The Teaching Manual on Plant Taxonomy
Anjula Pandey Kuldeep Tripathi K Pradheep S Rajkumar Veena Gupta
ICAR-National Bureau of Plant Genetic Resources Pusa Campus, New Delhi 110 012, India Pandey et al.
Citation: Anjula Pandey, Kuldeep Tripathi, K Pradheep, S Rajkumar and Veena Gupta (2019) The Teaching Manual on Plant Taxonomy. ICAR-National Bureau of Plant Genetic Resources, New Delhi, India, 119p.
Layout and design: Sh Shashi Kant Sharma
Cover page photo identity: (top to bottom) flowers of Vigna stipulacea, Papaver rhoeos, Abelmoschus tetraphyllus; herbarium specimen of Momordica cochinchinensis
Technical support: Ms Rita Gupta and Ms Urmila Singh
Published by: The Director ICAR-National Bureau of Plant Genetic Resources New Delhi 110 012, India
© 2019 ICAR-National Bureau of Plant Genetic Resources New Delhi 110 012, India
Printed at: Yugantar Prakashan Pvt. Ltd. WH-23, Mayapuri Industrial Area Phase-I, New Delhi-64 Ph.: 011-28115949, 28116018, 9811349619, 9953134595 E-mail: [email protected], [email protected] The Teaching Manual on Plant Taxonomy About the Teaching Manual
The ‘Teaching Manual on Plant Taxonomy’ has been developed for students of plant genetic resources (PGR) with an objective to provide an overview on taxonomy relevance to agriculture and PGR. The teaching course in PGR at ICAR-Indian Agricultural Research Institute, Post Graduate School was started in 1999 when taxonomy was included as a ‘core course’ in the discipline of PGR. Since then the syllabus in Plant Taxonomy for post-graduate studies was revised several times. Simplistic approach with basic understanding of various topics of taxonomy for the students coming from different backgrounds of agricultural sciences created interest towards better learning. Need to develop the “Teaching Manual on Taxonomy” was felt as there was insufficient information in various taxonomic treatises with respect to PGRs.
This manual contains ten chapters, including various concepts used in understanding the basic aspects of taxonomy covering theory and practical exercises. “Learning by observing” has been emphasized while conducting of practical exercises. Study of taxonomy has been demonstrated through use of few simple equipment like measuring scale, pen and pencil, dissection needle, hand- lens and dissection microscope. In this manual, for smooth flow of the text, some topics have been divided whereas others have been merged together with the relevant topics. The practical considerations are put in chapter 10 of manual including important families (only agriculturally important ones) to ‘How to describe’ a taxon. We hope that the contents are not only useful to the students of PGR but also the agriculturists, amateur scientists, non-taxonomists, parabotanists and others working in related fields. Technical terms have been simplified and put as the understandable words; botanical terms have been included to know the traits associated with the species.
The authors put on record the motivation and guidance by the Director, ICAR-NBPGR and Head, Division of Plant Exploration and Germplasm Collection, ICAR-NBPGR. While preparing this manual, contributions of our colleagues especially Dr ER Nayar the founder course leader for the Taxonomy Course in 1999 and other scientists particularly Dr KC Bhatt are greatly acknowledged. Chapter on Modern tools in Taxonomy for chemotaxonomy part was developed with the help of Dr R Bhardwaj and Ms Poonam Suneja, Division of Germplasm Evaluation, ICAR-NBPGR for which we greatly acknowledge their contributions. Our colleagues at the ICAR-NBPGR who have directly or indirectly helped in developing this manual but their names have not been reflected individually are also duly acknowledged.
Authors
The Teaching Manual on Plant Taxonomy Table of Contents
About the Teaching Manual
Introduction i
Theory
1 Plant Taxonomy in Relation to Plant Genetic Resources 1
2 Terminology Used for Plant Description 7
3 The Species Concept and Variation in Species 15
4 Rules of Taxonomy, International Codes of Nomenclature (ICN) and 21 International Code of Nomenclature : Cultivated Plants (ICNCP)
5 Taxonomic System of Classification 31
6 Biosystematics Studies on Crop Taxa 37
7 Modern Tools in Plant Taxonomy 47
8 Field Studies: Collection and Identification of Plants 59
9 Field & Herbarium Methods 65
10 Taxonomic Literature: Role in Plant Systematics Study 79
Practical Exercise
11 Study of Angiosperm Families 87 a Alliaceae 98 b Asteraceae 100 c Brassicaceae 102 d Cucurbitaceae 104 e Fabaceae 106 f Malvaceae 108 g Poaceae 110 h Rosaceae 112 i Rutaceae 114 j Solanaceae 116
References / Selected Readings 118
The Teaching Manual on Plant Taxonomy Introduction
Taxonomy is a basic science catering to other fields of science through its application. Majority of users working in agricultural crops are ignorant of taxonomic boundaries, intergeneric and intertribal hierarchy and hybridization potential in many crops. Traditional taxonomic methods generally use flowers, seeds and other identifiable parts to ascertain species the identity of a plant. But the Plant Genetic Resources (PGR) science deals with 'part of material' in the form of seed/or pod and vegetative propagules which are augmented while collecting and conserving the germplasm.
Taxonomy of crop wild relatives and their use in crop improvement has been studied in some important taxa but there exists a gap for less-known crop/potential/underutilized crops. ‘Seed and seedling biology as aid in identification’ goes beyond the traditional methods to resolve identity issues. Taxonomic treatment of agriculturally important families will facilitate in generating interest of the users in taxonomy and will guide them to be confident while working with PGRs. Some of the important issues on plant taxonomic research in India are: z Confusion arising due to presence of large number of morphological variants leading polymorphism and identification of new species/taxa z Neglect of taxonomy of cultivated plants by the genetic resource personnel and agriculturists z Difficulty in Taxonomic validation/authentication z Meager referable material (as herbarium specimens) and information z Missing evidences on source data on gross morphology vs. phylogeny of species of PGR value
Updating the knowledge on botanical nomenclature and information on economic plants is must before initiating an experimental work. There are many standard websites currently available - IPNI, Kew grasses, synonyms database, ILDIS database (for legumes), Conifer database, Checklist of selected families by Royal Botanical Gardens, Kew, Efloras, Species 2008, GRIN database, TROPICOS, etc. which can be used for validation; identification of voucher specimens of experimental material at herbarium can also serve as reference material.
Training of the scientific/technical staff in field of taxonomy and phylogenetics such as cladistics, phenentics, and molecular approaches is desired for holistic understanding of various aspects in taxonomy and systematics.
i
The Teaching Manual on Plant Taxonomy 1 Plant Taxonomy in Relation to Plant Genetic Resources
Introduction
Taxonomy plays a direct or indirect role in execution of major activities of PGR management including plant exploration and germplasm collection, exchange and quarantine, characterization/ evaluation and multiplication, conservation and documentation. The knowledge on taxonomy with reference to genepools of crop taxa and crossability aspects among the related taxa are well understood and applied in PGR science in a broader way.
In PGR management, correct identification of materials is the first step to enhance its utilization which can be achieved through knowledge of taxonomy. By furnishing correct information and references to a plant, an identifier helps all other fields of science. Unlike the traditional methodology used for identification of plants, identification of germplasm using material received as seed, vegetative buds, tubers, rhizomes, etc. for ex situ conservation requires good knowledge on taxonomy. Material incorporated into genebanks as unknown species or species identified only up to genus level (Triticum sp., Solanum sp., Mangifera sp.) or group level (as cucurbits, orchids, legumes) is of limited conservation and utilization value. Large germplasm holdings when processed for evaluation, seed increase or for growing out for validation have resulted into misidentification of the material. The PGR researchers should be familiar with fundamentals of plant taxonomy and identification procedures to enable them to identify the material.
Indian Council of Agricultural Research-National Bureau of Plant Genetic Resources (ICAR- NBPGR) is continuously involved in capacity building in field of PGRs including plant taxonomy teaching programmes affiliated to the Post Graduate School, ICAR-IARI, New Delhi in developing taxonomic skills among the students. Awareness on value of taxonomy was imparted through conducting various trainings, workshops and brainstorming sessions at various platforms. This chapter provides information on PGR management with special reference to plant taxonomy.
Plant exploration and germplasm collection
Plant exploration and germplasm collection activity pertains to the collection of materials from cultivated and wild habitats. In addition to knowledge of plant morphology, the details of characters of the propagules (seed/tubers, rhizomes, etc.) (e.g. in seed-shape, size, colour, seed coat texture, etc. and in vegetatively propagated materials-bulb/ rhizome shape, size, colour, etc.) are helpful to an identifier. In absence of such referable information and large number of floristic records, distinguishing closely related taxa is a challange.
Collecting germplasm: Germplasm collection and exploration missions are undertaken by ICAR- NBPGR in collaborative and independently for collecting targeted material in diversity rich areas. While collecting the germplasm, correct identification of material requires the updated taxonomic skill. Mistaken identity or wrong identification is generally observed due to limitation of knowledge
1 Pandey et al. base, lack of specialization and incomplete samples available for study. Species showing tendency for natural hybridization are generally confusing. A taxonomist, by virtue of his experience/studies on plant characters and distinct traits places a taxon in correct family, followed by genus and species. Diagnostic characters help in placing taxon to nearest matching of the taxon based on similarity of major traits. If taxonomists are not convinced of placement in best matched species, possibility of a new form/botanical variety, subspecies, species and genus may be presumed. Thus with accurate observations followed by plant description, identification, correct naming of plant can be achieved.
Collecting herbarium vouchers: Herbarium vouchers help germplasm collectors to identify species collected from particular areas. The germplasm of wild species, rare/ endangered species needs to be maintained as voucher (Pandey et al. 2003). Vouchers may represent range of variation from mass samples gathered from areas of occurrence, host species of diseased or pest samples, floristic records, less-known/ underutilized species collected from a site or any other experimental material kept for referral use (ref. NBPGR-NHPC vouchers). Complementary collections such as edible parts and products of economic value can make identification process easier. Specimens collected with detailed information on labels (habit, flower colour, bark characters, ethnobotanical uses) provide information for related studies.
Recording of passport data: Documentation helps the breeders in assessing the potential of the germplasm, the extent and magnitude of diversity and the cultural management practices followed across an area/ eco-geographic region (Refer to Chapter 8 for Annexure a, b).
The material submitted to ICAR-NBPGR by different stakeholders is checked for its essential descriptors like collector number, date and site of collection prior to the allotment of national identity number Indigenous Collector Number (IC No.) or for the conservation in National Genebank (NGB). The correct taxonomic processing for identity of the collected species especially of wild relatives and wild economic plants is essentially validated at this stage to avoid any confusion and to help utilization and for future planning. Special notes on big fruits/ perishable material are required during collecting and handling the germplasm. Range of variability of germplasm, even if not collected, have bird's-eye view on extent of variability. Photographic collections are also advisable in case of difficult to collect materials (bulky); and also for vulnerable or rare types.
It is difficult to note down all details of a species during collection but noted diagnostic characters serve as the most important clue in identification. Supplementary information on local / vernacular names, ecological data, associated flora, economic use, indigenous knowledge and associated information/ ethnobotanical notes, etc. are also helpful. But one should be sure not to use supplementary information in isolation to establish the taxonomic identity. Grow out tests play the safest and confirmatory role to fix the identity of germplasm in seed/ vegetatively propagated material.
Exchange and quarantine
ICAR-NBPGR undertakes exchange of desired germplasm (new crops, elite material, promising genetic stocks, improved varieties and wild species) for many desirable traits. Requests for germplasm exports are undertaken as per norms and MOUs signed by the respective countries. Every year large number of samples of diverse crops are introduced and processed for quarantine clearance and only the pest free germplasm is released to the users. The increasing import of
2 The Teaching Manual on Plant Taxonomy germplasm including trial material has enhanced the chances of introduction of unwanted pests/ pathogens. Need based supportive research is conducted for developing user friendly identification detection keys for facilitating weeds identification.
PGR scientists dealing with exchange and introduction of germplasm should have sound knowledge of host plants for pathogens, invasive and quarantine weeds (at least up to species level), distinguishing those species not covered under material transfer agreement (MTA), especially their propagules (including seeds) to avoid any chance of willful and non-willful default. Familiarity with knowledge on taxonomy, especially synonymy can help avoiding repeated introductions into the country, thus protecting the national interests.
Characterization of germplasm
The characterization and preliminary evaluation involve recording of highly heritable morphological characters and identifying promising accessions. Scoring of new characters of plant breeders use and evaluation of same is carried out at different agro-ecological zones of the country through its regional stations and networks with other organizations. Focus on identification of unique, distinct, newer and superior genotypes in crops are considered to be useful and most desirable.
Morphological and molecular characterization have proved more useful and powerful tools in establishing uniqueness and identity of a taxon. While evaluating germplasm, infraspecific variation (i.e. subsp./var./form) needs to be handled and studied properly, especially in data analysis and interpretation of results. Distinct and unique type of material, development of descriptors and descriptor states for database recording can be visualized with good knowledge on plant taxonomy. Visible traits linked with economic traits (for example quality traits/ pigmentation) may help to sort out F1 plants from their parents. Understanding on relatedness of crop wild relative (CWR) to the cultivated plants may serve as a guide for success in crossing programme including wide hybridization. Agricultural practices -rogue out of off-types and undesirable plant leading to genetic contamination due to crossability with progenitors/related wild relatives (especially when the transgenic crops) can be handled with adequate knowledge on taxonomy.
Conservation of germplasm
In ICAR-NBPGR, acquired germplasm from indigenous and exotic sources is conserved in the genebank. Orthodox seeds are conserved in seed genebank (-180C) for long-term (25-100 years) or medium-term (upto 10 years) depending on the use of germplasm. The materials stored in the long-term (called base collections) is generally not disturbed. Stored germplasm is routinely monitored for viability, quantity and seed health as per genebank standards. Working collections are maintained for routine research for use and distribution purpose.
The facilities of in vitro and cryopreservation are handling complementary collections like clonally propagated species and species producing recalcitrant seeds. Cryopreservation storage of material is done using liquid nitrogen (-1960C) with limited maintenance. Field genebanks maintain vegetative/ clonally propagated material at different National Active Germplasm Sites (NAGS) attached to various
3 Pandey et al. institutions in the country. There are chances of mechanical mixture during handling of germplasm from collection to conservation. It is mandatory to validate it with the help of expertise available, use of herbarium facilities (National Herbarium of Cultivated Plants, ICAR-NBPGR, New Delhi) and supportive aids like seed atlas/ literature.
Documentation and inventorization of PGR
Utilization of germplasm depends on the availability of passport information for an individual accession. The passport information on conserved material is centralized and updated for identified fields. ICAR-NBPGR has a computerized documentation system operational through AKMU/ Agricultural Research Information System. The databases dealing with PGR programmes include important fields- botanical name (valid name), synonym(s), local/ vernacular name, identification numbers (primary/ secondary identity) areas of collection, status (cultivated/wild), occurrence, uses, etc. In dealing with this, the problems of identity pertaining to correct botanical name (including correct nomenclature), synonyms, local/ vernacular name etc. are commonly recorded and thus there is need to have good knowledge base on taxonomy to overcome these complications.
Information based on taxonomic knowledge combined with floristic and exploratory studies brought out a scientific monographs on “Wild Relatives of Crop Plants in India” (Arora and Nayar 1984; Arora and Pandey 1996). To build up collection and study crop plant taxonomy and systematics was made to publish a document “Check-list of Crop Plants” based on systematics studies, literature, etc. These published inventories and documents are routinely referred by the users/PGR managers to check the identity related issues.
Taxonomic identification of PGR
The characters of roots, tubers, rhizomes, bulbs, stem, leaves, etc. in some genera/ species are useful key characters for identification (Porter1959; Lawrence 1951). Some of the notable features are habit (woodiness or herbaceous), characters of stipule, leaf (morphology, hairiness), root (nodules, aerial root system), fruit (capsule, pepo, berry), presence of exudates (milky juices or gums, resinous substances) and characters of specific parts in tree (bark, lenticels) and bamboos (spathe). The anatomical characters as presence of clusters of tissues in stem (Cucurbitaceae), specialized structures (oleoresin ducts in rhizomes in Zingiberaceae), bast fibres of unique nature (Urticaceae), seed/ seedling morphological characters, presence of endosperm, embryo type and aril on seed are useful key markers for taxonomic identification.
Observations on petals (presence or absence; if present whether united or free) give the primary subdivisions of dicots as apetalae (without petals) or polypetalae (separated petals) and sympetalae (united petals), perianth characters, ovary position (hypogynous, perigynous or epigynous). Family Cucurbitaceae is characterized by presence of inferior ovary. Sometimes the fruit characters are quick parameters for identifying the plant families. For example Cucurbitaceae (the melon family), Poaceae (the grass family), Malvaceae (the marsh mallow family) and Fabaceae (the pea family) represent unique fruit type and are readily distinguishable. The type of placentation such as the marginal, free central and basal placentation is generally associated with whole group or family.
4 The Teaching Manual on Plant Taxonomy
Synonym of a taxon is generally considered as a major factor responsible for confusions in identification and to be handled carefully while dealing with a taxon. Wider knowledge on variability pattern (in seed, seed coat, flowers, etc.) and factors responsible for phenotypic variation in a species (soils, irrigation, temperature), polymorphism, distribution range, plasticity, crossability/ swarm hybrids/ intermediate forms, etc. help character development in species.
While working in PGR, it is difficult to acquire detailed knowledge on characters of all taxa/ families of economic values. But one can attempt to narrow down the major/ economic plant families of much relevance to agri-horticultural crop-groups. Out of over two dozen families those having greater relevance to the PGR management (Poaceae, Cucurbitaceae, Malvaceae, Fabaceae, etc.) are significantly represented in the germplasm. Diagnostic characters of an individual family can help in understanding and provide clue to nearest possible level of hierarchy during collection/ conservation. To reduce the time the PGR workers can prepare a check-list /tips for family, genus and species characters that he intends to explore. Identification aids especially for seed/ propagules need to be developed region-wise or crop-group wise. For basic information, literature (monographs, floras, check-lists) and availability of materials of PGR relevance the readers may refer Arora and Paroda (1991) and Zeven and de Wet (1982).
National Herbarium of Cultivated Plants (NHCP) at ICAR-NBPGR, New Delhi, is a specialized herbarium, maintains collections of crop genepools comprising of wild, weedy taxa, primitive landraces, obsolete cultivars, modern cultivars, etc. both of indigenous and exotic plants provide the basis for PGR studies. Besides supplementary collections of seeds, economic products/ carpological samples, illustrations and photographic records are helpful in validating germplasm frequently handled as seed material or seed propagules (as rhizomes, bulbs, bulbils, tubers, etc.) and economic products. Holdings are complementary to that of the herbaria of the Botanical Survey of India (BSI), Kolkata, Forest Research Institute (FRI), Dehradun and National Botanical Research Institute (NBRI), Lucknow.
NHCP with over 23,000 herbarium specimens including digitital images of herbarium specimens added from diverse sources, including those collected during explorations, vouchers deposited of experimental studies, material under characterization, novel variants, ecotypes and natural hybrids are used for reference purposes.
NHCP works through linkages with other PGR based institutes (BSI, NBRI, SAUs, etc.) on aspects of taxonomy. PGR programmes in India can be strengthened with better linkages with national organizations (BSI, FRI, regional/ local herbaria, universities), researchers and experts in various crop groups and can facilitate the promotion of taxonomy in PGR.
Conclusions
The role of plant taxonomy in PGR science has been crucial and serves directly or indirectly to those involved in research, management, policy making and stakeholders in agricultural and non-agricultural fields.
5 Pandey et al.
Box 1: Difficulties in identification
z Preparing ideal voucher herbarium specimens during germplasm collection (due to plant attaining maturity).
z Lack of information on diagnostic characters of fruit, seed, rhizomes, bulbs and tubers.
z Lack of ecological, distributional or agronomic data particularly for wild species, related species, wild and weedy types of crop taxa.
z Separation of germplasm (seed) received from the bulk collections (as fruit) during assembling, sorting and indexing.
z Lack of expertise and thrust on taxonomic research and training/teaching.
PGR institutions must put an emphasis on taxonomic research pertaining to species of Indian origin and species having rich diversity. The following thrust areas need more emphasis: z Build-up of reference material (herbarium specimens, seed/economic product) for identification/ validation of taxa for desirable traits z Developing identification keys primarily based on vegetative characters/ seed/ propagules especially in problem taxa z Developing digitized identification tools/ databases of major economic taxa in the Indian perspective, and z Spreading awareness on value of taxonomy at various education levels through teaching/ trainings at schools, collages, universities, etc.
In view of the importance of taxonomy in PGR programmes, taxonomic research should be given high priority to revive and rejuvenate interest of students and scientists to find new dimension in this field of science.
6 The Teaching Manual on Plant Taxonomy 2 Terminlogy Used for Plant Description
Introduction
Plant description is an integral part of taxonomic data and it is intended to understand the biology of a species with minimum usage of words. The terminology helps improve readability and understanding of the contents and therefore facilitates in correct usage of terms and their universal meanings. In taxonomic and systematic study, the contents of description through use of terminology make it more consistent and standardized. It is an integral part of many books on botany/taxonomy that appears in the form of glossary. The purpose of this chapter is to guide the students for usage of right terminology in plant description. Students are suggested to observe a plant part, draw shapes or characters with pencil and then match with the standard drawings available, thereby choosing appropriate terms. Plant formal description of a newly discovered species, usually in the form of a scientific paper is in practice while publishing a new taxon. Readers must refer to chapter 8 on identification of plants for details.
Characters used for describing plants
There are two types of characters used for plant description: descriptive characters and diagnostic characters. Use of expanded characters for plant type: shape, size, colour, hairiness, etc. of plant part(s) are the descriptive characters. Among some of these characters those that can be used to identify and diagnose a species or taxon are called diagnostic characters. Example Luffa acutangula and L. aegyptiaca are two sponge gourds cultivated in India. Presence of striped angular fruit pericarp delineates the former taxon from the latter one. Colour of plant parts are not very variable and change with age of the plant, eco-geography, soil conditions, and temperature and therefore should be given lower weightage while using them for plant description and identification. Anthocyanin in petals is variable and same plant may show different shades in different habitats. For the sake of better understanding we will study terminology used for plant state- vegetative and reproductive. Descriptive and diagnostic characters in each category are discussed under the major category.
Vegetative
Plant habit
The terrestrial plant species may be classified as: woody plants (trees, shrubs, and lianas/woody vines). They typically persist over many growing seasons as above-ground woody plants. Herbaceous plants (sometimes called herbs) consist of succulent green tissue which does not persist through an entire year (typically dying back in winter). Plants which form rosettes of leaves close to the ground are an exception. Sub-shrubs are mostly herbaceous plants with a small amount of persistent woody tissue but the aerial parts dry out in off-season. Depending on their habitat of occurrance, plants may be aquatic (submerged, floating, emergent), or growing in very wet soil at edge.
7 Pandey et al.
The species may apparently show plants as upright (erect) or prostrate, growing completely flat on or along the ground. They may be decumbent (stems trail along the ground, but tips are erect), spreading (stems lie horizontal), or ascending (stems angle upward). Plants dependent on other plants or objects for support are usually considered to be vines. In order to sustain plant to grow actively climbers may develop thorns, tendrils, or branches (twiners) or other modified/ support systems.
Depending on the period of maturation and flowering species may be perennial (plant survives for more than two growing seasons and also produce flowers). Herbaceous perennials may dry down in unfavourable season but root system may survive and may regrow in next growing season. In contrast the annual plants germinate from seed, produce flowers and fruits and later die in one growing season completing their life cycle. Biennials germinate in one growing season, over-winter and reproduce in the next growing season.
Leaves
The leaf consists of a petiole (usually stalk-like) and an expanded blade. The leaf is attached to the stem at the node, while the length of the stem between leaf attachments is the internode. Either the petiole or the blade may be modified or missing; the leaves of some plants lack blades and consist only of petioles, flattened or not. Sessile leaves only have a blade. In other leaves, the petiole may be flattened to form a sheath, which encircles the stem; a ligule, a ridge of tissue at the top of the sheath, may be present. Leaf like structures, often present at each side of the point of leaf attachment are called the stipules. The space described by the angle between the upper side of the leaf attachment and the stem is called axil. The axillary bud may eventually expand to produce a branch or a flower.
Leaf venation is an important character for identification. Generally the lamina has most prominent central vein (the midrib). When other especially prominent veins are visible, they are called nerves. In leaves with net venation, two patterns of venation are possible. Secondary veins arise in two rows along the midrib in a leaf in pinnate venation, while secondary veins arise from a central point near the petiole in palmate venation. In leaves with parallel venation, all major veins are parallel to the midrib. Examples Musa paradisiaca (banana).
Leaf arrangement may be alternate, in which one leaf is attached at a node, opposite, with a pair of leaves at a node, or whorled, with three or more leaves at a node. Leaves may have an undivided blade (a simple leaf), or may be divided into leaflets (a compound leaf). Pinnately compound leaves are based on pinnate venation, with parts of the midrib exposed between individual leaflets. Palmately compound leaves are based on palmate venation, with leaflets meeting at a central point. Compound leaf has three leaflets, based on palmate venation.
A simple leaf can be distinguished from a leaflets through a compound leaf in presence of an axillary bud (simple leaves have them, leaflets do not). Based on leaflet number a leaf may be trifoliolate (three leaflets. Leaves may also show two or even three levels of compoundness; a twice- pinnately compound (bipinnate), thrice pinnately compound (tripinnate).
Terms for the shape of the leaf apex and leaf base are illustrated in Fig. 1. Commonly used terms are peltate leaves (round, with a centrally attached petiole) example Nymphaea, lotus; perfoliate leaves (sessile, with the leaf base entirely surrounding the stem- Brassica, Sonchus), decurrent leaf
8 The Teaching Manual on Plant Taxonomy bases (continue down the stem as ridges of tissue). Leaf margins may be entire (lacking teeth or indentations), or have extra growth as toothed, or lobed or spines, etc.
Leaves may be pinnately lobed (based on pinnate venation) or palmately lobed. Deeply lobed leaves, with sinuses extending three quarters of the distance from the margin to the midrib or more, are called divided. Leaves divided into many narrow segments, producing a feathery appearance, are dissected or parted (Fig. 1) for example coriander Coriandrum sativum. In lobed, divided, and dissected leaves some tissue of lamina remains along the midrib, in contrast to compound leaves. the terminology used for different types of leaf margins is illustrated in Fig. 1.
Fig. 1. Terminology used for vegetative characters (Source: Graf 1982)
Plant surfaces
Plant surfaces are the most typical and identification morphological marker characters especially the bark in trees, fruit surface in okra. Two varieties of wild Abelmoschus, A. manihot var. tetraphyllus and var. pungens are differentiated on the basis of hairiness of surface of fruits. A surface without
9 Pandey et al. hairs is glabrous and hairy surface is called 'pubescent'. A pilose surface is covered with fine, thin hairs, while a tomentose surface is densely hairy. Hairs may have special shapes, such as hooked or stellate (star-shaped). A glaucous surface is noticeably waxy; a glandular surface has visible, often darker, glands. Surfaces may be punctate, with tiny depressions, or tuberculate with small protrusions (Abelmoschus tuberculatus with tuberculated hairs on fruits distinguish it from other wild okra species). Surface extensions in the form of prickles or tubercles (sharp pointed present on plant surface), or thorns (hard, sharp modified branches present on leaf axils) or modified parts are seen in species of Acacia, Ziziphus, etc.
Reproductive parts
Plant description provides an essential clue for identification numbers of floral parts are sometimes shown in ranges; with numbers in parentheses representing unusual conditions. Description as: small, monoecious (look for two sexes of flowers on one plant); flowers regular, unisexual (staminate or pistillate), small, 1-2 per leaf axil (either condition is likely); sepals 0; petals 0 (sepals and petals are absent); stamens 1-3(5) (usually 1-3 stamens, but can have up to 5); pistil 1, styles 2 (a single ovary with two styles); ovary superior (a longitudinal section will show that the ovary located on top of the receptacle), 4- celled (a cross-section of the ovary will show four compartments); fruit splitting.
Inflorescences
Flowers occur in arrangements which are often characteristic of the plant species. The entire flowering portion of the plant, including flowers, “stems” (pedicels), and bracts, is referred to as the inflorescence. When the flower or inflorescence is at the top or end of the stem peduncle, it is terminal. When the inflorescence or flower is located in an axil (usually subtended by leaves), it is axillary (or lateral). Solitary flowers are often terminal, sometimes on a scape arising from a rosette of leaves. Flowers on pedicels along a single unbranched axis, erect or drooping, form a raceme (Fig. 2). When pedicels are not present, the flowers are sessile and the inflorescence is a spike. The basic branched inflorescence is the panicle, in which pedicels are located along several branches arising from a central axis. In an umbel, all pedicels arise from a central point, with the flowers arranged in a flat plane or a convex rounded cluster. An scape is a peduncle/leafless flower stalk rising from the ground or from a subterranean stem, as in the stemless violets, tulips, alliums. A corymb has a similar appearance, but the pedicels arise at different points along the stem. Both the umbel and corymb may be compound, with different tiers of pedicels within the inflorescence (compounded umbel). Combinations of two inflorescence types may occur, such as a panicle of racemes (Fig. 2). The cyme may take many forms, but is always characterized by a single central flower which matures before the rest of the inflorescence. The head is composed of flowers tightly arranged on a flat or discoid axis. Typical inflorescence of the Araceae is the spadix, a fleshy spike, subtended by a large bract, the spathe. Catkins are typical of many taxa in Moraceae, Piperaceae (spikes or racemes of unisexual flowers). Single flowers, racemes, cymes and capitulum are unique to family and taxa.
Flowers
Floral/ reproductive plant characters are the most stable characters and are very important in classification of plants. Taxonomic keys based on morphological characters of the flower or fruit characters. A description of the typical floral structure is included in each family description. For keys details refer to Chapter 8.
10 The Teaching Manual on Plant Taxonomy
Flowers are attached to plants with stalk (pedicel); pistil (or pistils), stamens, petals, and sepals are attached to the receptacle. When both stamens (containing male gametes) and pistil (containing female gametes) are in the same flower, the flower is perfect; when only one of these organs is present, the flower is imperfect. If flowers are imperfect but flowers of both sexes (both staminate and pistillate flowers) are present on one plant, the plant is monoecious. When a single sex is present on one plant (i.e., two plants of different sexes are necessary for pollination),the plant is called dioecious. Based on symmetry flowers may be regular (radially symmetrical) with all parts of a whorl being the same size and shape called actinomorphic. A cut through more than one direction to produce two similar halves decides the state of flower (flower actinomorphic). Irregular flowers (bilaterally symmetrical) have floral parts grouped or fused in a way that a cut through only one plane will produce two equal halves or they may be entirely asymmetrical (zygomorphic flower).
A pistil consists of an ovary containing one or more ovules (which develop into seeds), the (often) slender style, and the stigma is the receptive surface at the tip of style. The pistil is formed from one or more ovule-bearing units known as carpels. The number of carpels included in a pistil (often) can be determined by counting the number of styles and/or stigmas arising from the ovary. The interior of the ovary is often divided into chambers called locules. Their numbers are noted in family descriptions as, for example, tricarpellary ovary in Cucurbitaceae. Generally the number of locules is related to the number of carpels, but at times due to development of septa they may be more or less in number. A flower may have more than one pistil; in such flowers, each pistil consists of a single carpel and each style can be traced to a different ovary.
The position of the ovary with respect to the receptacle is also an important character. The ovary may be above the receptacle, so that the petals and sepals are attached beneath the ovary this is a superior ovary. When the ovary is enclosed by the floral tissue, so that the petals and sepals are attached at the top of the ovary, it is an inferior ovary. However, to determine whether the ovary of a flower is superior or inferior, it may be helpful to use a knife to make longitudinal cut through the center of the flower.
A fertile stamen consists of a slender filament and the anther, which contains pollen. Some stamens may be sterile, meaning that a stamen-like structure exists without a pollen-producing anther. This sterile stamen are called staminode may also be petal-like (petaloid) in appearance, i.e., expanded and coloured stamens. The fusion of filaments with each other (so that they are connate) or the other floral parts can be significant in identification. The sepals and petals together are the perianth of the flower. The number of sepals (together called the calyx) and petals (the corolla) is often an important character; a plant description might indicate parts in 4s” or that the “calyx and corolla are 4-merous”. While the sepals of most plants are green, they may sometimes be petaloid. In some flowers, it is difficult to distinguish sepals from petals, thus the plant description may simply refer to tepals (examples Allium cepa; Alliaceae). The sepals and petals may be separate (free; polysepalous, polypetalous) or more or less fused to one another (united, gamosepalous, gamopetalous).
There are other extra floral specialized parts known as bracts. In Euphorbiaceae, the bracts may be coloured or otherwise prominent and resemble petals. A tightly organized arrangement of bracts called the involucre forms the base of the head of the Asteraceae and is also present in flowers of some other families. Spathe (banana), epicalyx (okra) are some more extra floral parts distinctive of a taxon.
11 Pandey et al.
Fruits
The type of fruit produced in a taxon is often a key character for plant identification. Fruits are the ripened ovaries of flowers, contain the seeds, and may include accessory structures. Some types of fruit are dry at maturity, while others have a fleshy fruit wall. Indehiscent dry fruits do not open to release seeds at maturity. The fruit wall and the seed coat are fused together in the grain, the characteristic fruit of the Poaceae. The achene is also a small single seeded fruit, with a dry thin fruit wall closely appressed to the seed coat. Wings or other appendages may be attached to the achene; a samara is a winged achene typical of some woody plants Ailanthus altissima, maple. A utricle is a small single-seeded fruit resembling an achene, but with the fruit wall loose from the seed coat. Nuts and nutlets are dry indehiscent fruits with hard fruit walls. Sometimes there is an involucre attached to the nut, as in the acorn (the characteristic fruit of Quercus spp. oaks).
Fig. 2. Terminology used for reproductive characters (Source: Graf 1982)
12 The Teaching Manual on Plant Taxonomy
Dehiscent dry fruits open at maturity and release seeds (Fig. 3). The capsule develops from an ovary with more than one carpel and seeds are released when the capsule opens at the top or sides. A follicle forms from one carpel and splits along one seam. A legume is also formed from one carpel but splits along two parts (Fabaceae). In silicle and silique each split along both sides, leaving a membranous partition in the middle; they are typical of the Brassicaceae. Dry fruit wall which separate from one another during dehiscence are called valves. A schizocarp arises from an ovary where the mature carpels split away from one another, so that each unit (a mericarp) resembles an entire indehiscent fruit; for example fruits of Apiaceae (the coriander family).
Fig. 3. A key to the main types of true fruits
Fleshy fruits are all indehiscent. The berry is several-celled (though partitions may not be visible at maturity) and many-seeded. Hesperidium is a type of berry in which septation and leathery rind occurs (Example Citrus). A drupe has a single, usually large seed. A pome is typical of some Rosaceae (Malus), in which the swollen, fleshy receptacle encloses the papery fruit wall.
Conclusions
Due to the limitation of space here it is not possible to cover all the terms used while describing a taxon through terminology description. However, understanding of the importance of usage of right term(s) in describing taxa will open up a new vision among the students dealing with taxonomy. Glossary and links can be refered for detailed knowledge on meanings of descriptive terminology (Lawrence 1951).
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The Teaching Manual on Plant Taxonomy 3 The Species Concept and Variation in Species
Introduction
The term ‘‘Species” is a Latin word which means ‘kind’. It is frequently used by the taxonomists and systematists worldwide. Species is a basic unit of biological classification used for ranking the group of similar organisms showing the same level of hierarchy. Putting in simpler words, the organisms with morphological similarities are grouped in one ‘Species’.
For a long time, the taxonomists were not able to properly define ‘Species’ and ‘Species boundaries’ to determine the variation in species. This has resulted in development of several concepts. These species concepts are well understood through the process and factors leading to the process of speciation. Better understanding of these concepts is likely to create a practical classification system.
Speciation is the origin and evolution of populations in genetical processes (Davis and Heywood 1963). Different steps in speciation are: origin, expansion and spread, isolation of species and decrease and extinction of population. Abrupt and gradual changes in species may result into development of races and species. Differences in ecological, geographical and cytological factors may result into “abrupt speciation”. Whereas the character variation developed in a species due to the process of mutation, selection, isolation and gene recombination leads to “gradual speciation”.
The key factors such as natural selection and environmental factors have played a key role in developing species “as the fundamental units of evolution” (Charles Darwin 1809-1882). The genetics deals with focus on the understanding the species evolution led to development of modern species concepts. The “Biological species concept” developed in the late nineteenth century was one of the most widely accepted concepts. The modes of speciation could be well explained on the basis of the geography (sympatric, allopatric and parapatric) and chromosomal biology. Several studies explaining this concept depend on species delimitation, ecological and interactive factors (the biotic and abiotic).
Species is the basic identifiable unit of natural diversity and the most commonly used category of the classificatory systems by the taxonomists. The taxonomists proposed various phenetic or phylogenetic concepts for classification based on different theories. This chapter mainly discusses some of the important species concepts and the merits and demerits of each one of them. Some selected terms explained in Annexure I can facilitate better understanding of the contents of this chapter.
Study on variation patterns in plants
The concepts of variation in species in general and genetic diversity in particular are important for basic activities in PGR programme from collection to conservation. The natural variation in plant
15 Pandey et al. species represents genetic diversity of a single wild plant which is beneficial traits for plant breeding. Variations in plants can be grouped under: interspecific and infraspecific variation. Study on variation patterns within a species in natural habitat can be studied using biosystematics approach through the following steps:
1. Collection of plants: From distinct habitats, ecotypes recognition, recognising clinal patterns, across the range of distribution of the species; for role of environmental factors in modification and changes in genotypes within population 2. Assessing environmental impact: Growing plants in uniform conditions to assess the genetic basis of variation; study of crossability and hybrid distinctness; reciprocal transplants; experimental studies of the population in relation to the environment (ecotypes) 3. Biosystematics study: Using species as the unit of study genus (examples: Allium, Trichosanthes, Luffa, Amaranthus ) 4. Study on adaptability: Species variants created due to adaptation to different set of environment- ecospecies 5. Genetic barriers: Artificial barriers in a species lead to changes in characters over period of generations
Variation within populations may be with respect to the phenotype and phenotype versus genotype. Studies on biosystematics using populations as the unit of study in genus include: wild/weedy Oryza populations growing along fields of paddy, extending to the forest margins, waterlogged areas, and annual to perennial forms. Contiguous populations occurring as complex of species which may not be clearly delineated a distinct taxon- Oryza sativa var. spontanea or O. nivara- O. rufipogon.
Species and species variation
The concept on species and species variation was proposed by John Ray (1627-1705). He defined species as “groups of plant truly breed within their limits of variation” (Ray 1686). A new definition of species concept mainly based on the floral and sexual characters was proposed by Linnaeus (1707– 1778) in his publication ‘Species Plantarum’ (Linnaeus 1753). Species as the definition proposed by De Candolle (1778–1841) is ‘‘a collection of the individuals resembling each other more than they resemble anything else and can naturally produce fertile individuals”. He classified plants into - vascular and non-vascular plants groups. His major contributions are the introduction of term ‘taxonomy’ and the species concept presently being used by the taxonomists with some modifications.
Modern species concepts
The phenetic classification system was based on similarities between the organisms without the support from the evolutionary evidences. This approach needs data from different fields of science- morphology, cytology, phytochemistry, embryology, anatomy, etc. Approach for the phylogenetic classification also called cladistic classification is based on development of characters in the organisms during in evolutionary process irrespective of their present state.
Some of the important species concepts are given below:
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Biological species concept
According to ‘‘Biological Species” concept (proposed by Mayr 1942) the species are defined as: ‘‘groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups”. Distinct biological species do not interbreed even when growing in the same natural environment despite of their relatedness. This species concept is not applicable to asexual organisms and to the allopatric populations. The reproductively isolated populations remain discontinuous from all other species.
Morphological species concept
The morphological species concept is defined as species as smallest group of organisms distinguishable in the form of a community, or a number of related communities, having distinct morphological characters so as to discrete them for specific name. Species can be identified by morphological gaps in variation between individual plants. For example a population of Primula veris and P. elatior, considered as variety of the same species having many intermediate forms between the two distinct species. Identification of morphological characteristics in a species depend on ‘expert’ opinion. The species despite of their sympatric lineage (morphologically indistinguishable) may arise from different lineages.
Ecological species concept
This concept deals with populations constituting distinct discrete phenetic clusters identified as species on the basis of ecological and evolutionary processes. Ecological competition among the species leads to adaptation for particular environmental conditions (niche). Closely related species occupying a niche area demonstrate the differences between species in form and behavior are often related to differences in the ecological condition where they are occurring. Likewise two similar organisms likely to overlap in their ecological need may belong to same species. There are some issues such as divergent forms of an organism grouped into new species during identification; and the degree to which species are competing ecologically may lead to differences in life forms.
Cohesion species concept
Cohesion species concept is based on role of micro evolutionary factors as influenced by the process of gene flow, genetic drift, natural selection, etc. As per the cohesion species concept the population genetic stress results into origins of phenotypic similarity within species.
Phenetic species concept
The phenetic species concept is based on measuring large number of characters in organisms to classify them into discrete phenetic clusters using multivariate analysis. As per this analysis the smallest unit in the group with greater similarity is classified under a ‘species’. The degree of phenetic similarity is measured in terms of phenetic remoteness. Some of the limitations in this concept are: that the members of the same species may be phenetically very different and very distinct species may resemble too much. Two distinct taxa (units) may have overall similarity as a result of resemblance
17 Pandey et al. in several characters. The data generated from phenetic classification or numerical classification (numerical taxonomy) organizes information is more presentable.
Phylogenetic species concept
Several theories such as Darwin and Wallace theory of evolution, the rediscovery of G. Mendel’s laws of inheritance in 1900 and the modern chromosome theory have led to development of the cladistic speciation. Species having high degree of similarities in some unique traits are grouped in monophyletic clusters based on the discriminative phenotypes. The phylogenetic species concept emphasizes on the degree of relatedness of a new taxon to previously defined taxon. This concept has merit over other concepts due to as it is applicable to the sexual and allopatric populations.
Conclusions
The species concepts discussed above can be applied to those individual(s) having sexual reproduction in same community or geographical region(s). Sometimes more than one concepts may be applied in combination (for example the ecological species concept with morphological and phenetic concept separately or in combination). The phylogenetic classification considers the evolutionary changes in organisms leading to characters modification(s) due to divergent transformation. The following criteria may clearly explain the meaning of ‘‘species”: z Close resemblance between the individuals in a way to ‘sufficiently identify them as distinct’ members of that group. z Confinenement of individual(s) or population to the geographical area occupied by a species adapted to the environmental conditions. z Crossability between the individuals with no or meager loss of fertility.
An ideal species concept would be the one to explain the lineage from the most primitive to the most advanced organism and to classify each one of them to define its origin in terms of monophyletic or polyphyletic.
18 The Teaching Manual on Plant Taxonomy
Annexure I
Terms used in this chapter
Biosystematics: comparative study of taxa using evidences from the discipline of morphology, cytology, genetics and ecology to understand micro-evolutionary process operating in populations, define and delimit biological units and categorise them.
Biotype: a collection of individuals that are genotypically the same
Hybrids: introgressed forms leading to new variants
Infraspecific variation: can be explained under the following categories:
Form: sporadic variant, different in a single or few characters, no distributional differences
Variety: a local type of variant; with morphology and differences in characters
Subspecies: more or less separated by a combination of characters but not usually isolated genetically; i.e. it is a regional representation
Ecotype: is the unit of variation within population that is the product of the reaction of the genotype of the species with the environment
Genecology: study of the patterns of variation within species in response to habitat factors
Population biology: study of micro-evolutionary factors
Tests of characters: repeated evaluation of varied material and recording data on observations in the field and in cultivation, and then analysis using statistical methods
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The Teaching Manual on Plant Taxonomy 4 Rules of Taxonomy, International Code of Nomenclature (ICN) and International Code of Nomenclature for Cultivated Plants (ICNCP)*
Introduction
Taxonomy forms the major part of systematics and includes description, identification, nomenclature, and classification. Taxonomists are basically involved in determining what is a species (or their subdivisions), distinguishing these from others through keys and descriptions and geographic boundaries and thereby mapping their distributions and determining proper names of species and higher order ranks (as genera or families) using international rules of nomenclature.
Plant nomenclature is the process of assigning the correct names to plants using an established system of nomenclature. They provide communication of information and are essential for classification. The rules of nomenclature referred to as “Code” are formally listed in the International Code of Nomenclature for Algae, Fungi and Plants.
Plants are identified with the common names (vernacular, local or folk names) or scientific names. In contrast, botanists use scientific names to address plants.
Box 1: Why use of the 'common names' creates problem in their usage
z They are not universal; may vary from language, region of use and country to country (scientific names are universal, globally accepted and used).
z They may not provide any information regarding the interrelationship of plants.
z There may be more than one common name(s) for a species or sometimes two or more plants may have same common names.
z Some rare or un-common species may not have any common names.
There is one scientific name as correct name (only in case of taxonomic dispute in naming). They are always written in the Latin alphabet and italicised.
Polynomial Nomenclature: the system was followed by many botanists during eighteenth century. Such names were composed of several words based on brief description of the plant. For example: Salix pumila angustifolia altera. These names were difficult to remember and also to prepare identification key. Linnaeus replaced this polynomial system of nomenclature by binomial nomenclature.
*adapted from Pradheep et al. (2015)
21 Pandey et al.
Binomial Nomenclature: a scientific name is a binomial made up of generic name and specific epithet. The species name consists of both the generic name and specific epithet. A complete binomial is always followed by the name of person(s) who originally described the plant. For example, the complete scientific name of common onion is Allium cepa L. Allium is genus epithet, cepa is specific epithet, and L. (Linnaeus) is the author or authority. Thus, species name of common onion is Allium cepa L.; similarly okra binomial name is Abelmoschus esculentus (L.) Moench.
Generic epithet z It is a singular Latinized noun or a word treated as noun. z It is always written with initial capital letter. z If a generic name occurs more than once in a citation, it may be abbreviated by using initial capital letter. For example: Brassica alba, B. nigra, B. juncea z The generic name can be taken from any source; it can be an aboriginal name. Many ancient common Greek names like Asparagus, Narcissus have been adopted as generic names. z It may be given in honour of a person. Example: Linnaea, Bauhinia, Caesalpinia. z Generic name may depict a certain characteristic of a plant. Example: Rhododendron (colour of the wood is red), Xanthoxylum (yellow wood).
Specific epithet z It is always written with small initial letter. z It depicts distinguishing feature of the species like colour, shape, size, habit, habitat etc. [Solanum nigrum (black nightshade) and Calotropis gigantea (big size)]. z It may be given in honour of a person, or may be derived from an old common name, a geographic locality, or some characteristic of plant, or they may be even composed arbitrarily. z It may consists of two words are hyphenated. Example Trigonella foenum-graecum L.
Rules of plant nomenclature and codes
Botanical nomenclature requires knowledge of Latin. The rules of plant nomenclature govern and deal with formal botanical names that are given to plants, fungi and a few other groups of organisms, all those “traditionally treated as Algae, Fungi, or Plants”. The International Code of Nomenclature for Algae, Fungi, and Plants (ICN), was formerly called as International Code of Botanical Nomenclature (ICBN). The name was changed at the International Botanical Congress in Melbourne in July 2011 as part of the Melbourne Code which replaces the Vienna Code of 2005. The code is updated periodically at the International Botanical Congresses at the interval of six years. The ICN can only be changed by an International Botanical Congress (IBC), with the International Association for Plant Taxonomy providing the supporting infrastructure. Each new edition supersedes the earlier editions [now latest code is Schezwan Code (2017)]. Rules for naming of the cultivated plants are dealt in a separate code called 'The International Code of Nomenclature for Cultivated Plants (ICNCP)'.
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In addition to the change in the title of the Code, there were five other major changes to the rules of nomenclature adopted in the 18th ICB held in Melbourne, which are:
1. Electronic publication of names of new taxa permitted from January 1, 2012: Thus new names can be published in Portable Document Format (PDF) in online publications with an International Standard Serial Number (ISSN) or International Standard Book Number (ISBN). This means that it will no longer be necessary for new names of fungi, algae and plants (and designated types) to appear in printed matter in order to be effectively published. No longer will it be a requirement to deposit some paper copies in libraries.
2. Language for description and/or diagnosis: New publication can be either in English or Latin language. Earlier, it was necessary to provide a description and/or diagnosis in Latin, in order to validly publish name of a new taxon.
3. Registration of fungal names: Starting on January 1, 2013, all new fungal names, including new taxa, new combinations, names at new ranks, and replacement names, must have an identifier issued by a recognized repository. After this date new fungal names published without an identifier from a recognized repository are not considered to be validly published. In the past ten years, an increasing number of mycologists have been using MycoBank (www.mycobank.org) to register new fungal names. A unique number is issued by MycoBank for each registered fungal name, which serves as an identifier to be cited in the publication where the name is proposed. Recently it was decided that three repositories may serve as official repositories of fungal names, i.e., MycoBank, Fungal Names (fungalinfo.im.ac.cn/fungalname/fungalname.html) and Index Fungorum (www.indexfungorum.org).
4. One fungus one name: Over more than a century the Code has allowed the use of separate names for asexual stage (anamorph) and sexual stage (telomorph) of pleomorphic fungi. Using modern tools of identification like - molecular tools sexual and asexual phase of one fungal species has been put as one. Starting on January 1, 2013, the dual naming system for pleomorphic fungi, fungi with asexual state (anamorph) and sexual state (teleomorph) is replaced with one scientific name for each species based on priority.
5. One fossil one name: Earlier Code has permitted to use separate names to different parts of a fossil plant called as “morphotaxa’. The Melbourne Code has now put one fossil to have only one scientific name (in case if two or more morphotaxa are of the same organism).
First proper set of rules of nomenclature of plants was drafted by Alphonse de Candolle and passed by the International Botanical Congress at Paris in 1867. The code is known as Paris Code. Subsequent Congresses and codes like Rochester Code (1882), Vienna code (1905), American code (1907) and Brussels’s code (1910) discussed various aspects of nomenclature and suggested many modifications and amendments in the rules. Two codes, American vs. European, existed till late 1800s and early 1900s. Efforts were made to harmonize the basic difference between the Vienna and the American codes at the Fifth International Botanical Congress held in Cambridge in 1930 and for the first time in botanical history, a code of nomenclature came into being that was international in function as well in name. International Botanical Congress is held at an interval of 5- 6 years and the code is named after the name of the place where the congress is held. Several
23 Pandey et al. changes have been made in the code during the last 100 years and now the rules of nomenclature are almost stabilized.
According to the code May 1, 1753, the date of publication of Linnaeus’ Species Plantarum, is considered the starting point of present day nomenclature. Over the period of time several versions of code have been published, the most recent one is Melbourne code which the XVIII International Botanical Congress adopted in 2011. This supersedes the earlier Viena Code (2006).
The code is divided into three divisions and five appendices: The Divisions: are: I. Principles; II. Rules and Recommendations; further divided into 07 Chapters and 62 Articles; III. Provisions for the governance of the of code
Appendices
I. Names of hybrids IIA. Nomina familiarum, fungorum, pteridophytorum et fossilium conservenda et rejicienda (conserved and rejected family name of fungi, pteridophytes and fossils) IIB. Nomina familiorum bryophytorum et spermophytorum conservenda (conserve bryophyte and spermophyte family names) IIIA. Nomina generica conservends et rejicienda (conserved and rejected generic names) IIIB. Nomina specifica conservenda et rejicienda (conserved and rejected specific names) IV. Nomina utique rejicienda (rejected names and all combinations based on these names) V. Opera utique oppressa (list of publications and the category of taxa that are not validly published)
The principle forms the basis of botanical nomenclature. The detailed provisions of the code are divided into rules, set out in the articles and recommendations. The main objective of the rules is to put nomenclature of the past into order and also provide for that for future. Names contrary to rules are considered illegitimate and cannot be maintained.
Box 2: Principles of ICN
I. Botanical nomenclature is independent of zoological and bacteriological nomenclature. II. The application of the taxonomic groups is determined by means of nomenclatural types. III. The nomenclature of a taxonomic group is based on priority of publication. IV. Each taxonomic group with particular circumscription, position and rank can bear only one correct name, the earliest that is in accordance with the rules, except in specified cases. V. Scientific names of taxonomic groups are treated as Latin regardless of their derivation. VI. Rules of nomenclature are retroactive unless expressly limited.
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Some significant rules
1. Taxonomic hierarchy
It was Linnaeus who for the first time introduced hierarchical classification by placing each organism into a layered hierarchy of taxonomic categories or groups. Different groups of plants classified for taxonomic purposes are called taxa. The principle ranks of taxa in descending order are: Kingdom, Division, Class, Order, Family, Genus and Species. Thus, each species is assignable to a genus, each genus to a family and so on.
I. Names of taxon above the rank of family are treated as plural noun and are written with an initial capital letter. Such names are generally based upon the name of an included genus, called the type genus. Each rank has a distinctive ending that is attached to the stem of the type genus. Suffixes used to form these names are: -aceae for family (e.g. Magnoliaceae, ending on the genus Magnolia); - ales for order (Magnoliales); - opsida for class (Magnoliopsida) ; -phyta for division (Magnoliophyta)
II. Names of genera are treated as nouns in the nominative singular, underlined (or italicized), and the first letter is capitalized.
III. The scientific name of a species is a binary combination consisting of the name of the genus followed by specific epithet.
IV. The specific epithet is usually considered to be an adjective; it is also italicized or underlined and written in all lower case. The specific epithet may be derived from any source, or may even be composed arbitrarily.
V. The scientific names include authority (name of the person who described the species); the author’s name is never italicized or underlined. Author’s names are generally abbreviated L. (vs.Linn. for Linnaeus).
VI. Alternative family names. Some family names, which were not according to rules. The code has suggested alternative names for such families (use of both is allowed by the code). Eight families where old names and their alternative names are give: Cruciferae (Brassicaceae); Guttiferae (Clusiaceae); Leguminosae (Fabaceae); Umbelliferae (Apiaceae); Compositae (Asteraceae); Labiatae (Lamiaceae); Palmae (Arecaceae) and Graminae (Poaceae).
2. Rule of priority
Priority of publication is an important part of the rules of nomenclature. Each family or taxon of lower rank can have only one correct name special exception being the families mentioned above. The earliest legitimately published name is the correct name. The correct name of a species is the combination of the earliest validly published generic name with the earliest validly published specific epithet, except in cases of limitation of priority by conservation. Conserved names are legitimate even though initially they may have been illegitimate. The conserved names may be at level of family, genus or species. The same taxon may have been given different names by different workers; the later names are called ‘synonyms’ and are illegitimate.
25 Pandey et al.
Priority begins with the date of publication of Linnaeus’ Species Plantarum (May 1, 1753) for Spermatophytes and Pteridophytes, and applies to the rank of family and below. Publication of the names of Spermatophytes and Pteridophytes earlier than 1753 has no status of priority. The principle of priority does not apply above the rank of family. Principle of priority has also been limited for other groups of plants by ICN.
3. The type method or typification
The names of taxonomic groups will be based on nomenclatural types the principle II and rules of ICN. This means that all names are permanently attached with some taxon or specimen designated as type. For species and infraspecific taxa the type is a specimen on which the species was based and originally described. Names of the taxa above the species, viz. genus, family etc. are based on the name of that immediate lower taxon on which that group was originally based. For example, the family Lamiaceae was based on the genus Lamium, and thus, Lamium is the type genus of the family Lamiaceae. Manisuris myuros L. was the species on which the genus Manisuris was based and thus Manisuris myuros is the type species of the genus Manisuris. The principle of typifcation does not apply to names of taxa above the rank of family.
Box 3: Different 'types' designated by the Code
Holotype: is that single specimen (which may be whole plant or part of a plant) designated by the author of the species to represent the type of the species. As per the nomenclatural rules, it is obligatory to designate the 'holotype'.
Isotype: are the duplicate specimens of the same plant from which the 'Holotype' was made; collected from the same place, same time and by the same author.
Syntype: any specimen cited in the protologue when no holotype was designated, or any one of two or more specimens simultaneously designated as types.
Lectotype: a specimen or illustration designated from the original material as the nomenclatural type, if no holotype was selected at the time of publication, or if holotype is missing.
Paratype: the specimens other than the holotype and the Isotypes studied by the founding author at the time of describing new taxon are called 'Paratype'.
Neotype: if Holotype, Isotype, Syntype or Paratype are lost, or are not available, a specimen from the describing locality or illustration is selected to serve as nomenclatural type is called 'Neotype'.
Epitype: a specimen or illustration selected to serve as an interpretative type when the holotype, lectotype or previously designated neotype, or all original material associated with a validly published name, is demonstrably ambiguous and cannot be critically identified for purpose of the precise application of the name of the taxon.
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Valid and effective publications: Requirements of the code for the publication of new names are: z The name must have proper ending for its rank, for eg., -ceae for family,-ales for order. z The name of the author and the rank must be given. z The name must be accompanied with a full description and a diagnostic description either in Latin or English. z The nomenclatural type must be designated. z In case of new combination, the full reference of the basionym must be given.
The publication is made effective by making printed matter available to the scientific community through its publication in a journal and its distribution to the libraries. However, Melbourne code has permitted electronic publication; hence no longer will it be a requirement to deposit some paper copies in libraries.
Author citation: A botanical nomenclature, author citation refers to citing the person(s) who validly published a botanical name. Author’s name provide historical information about the plant i.e. when and where was the name published. The names of the authors are generally abbreviated.
Single author citation: Linnaeus gave the name Argemone mexicana, and hence it should be written as Argemone mexicana L.
Multiple author citation: z If two or more authors are associated with the publication of a new species, their name are joined by et or &, e.g. Millettia auriculata Wight et Arn. or Wight & Arn. z When a name proposed by one author is published validly by another author, the name of two authors are linked by ex, e.g. Berberis asiatica Roxb. ex DC. z If an author publish a new species in the work or publication of another author, the names of authors are linked by in, e.g. Nepeta ciliaris Benth. in Wall. z Parenthetical authors denote a change in the name of a taxon by transfer or by upgrading or downgrading the level of the taxon. When a species is changed from one genus to another, the name of the author whose specific epithet is being used in the changed name is placed within parenthesis, and the author who made the change outside the parenthesis, e.g. Leucas nutans (Roth) Spreng., based on the basionym Phlomis nutans Roth. (genus Phlomis changed to Leucas). z When the circumscription or the diagnostic characters of a taxon are altered, the names of original author and the author who has made the changes is joined by “ emend”. e.g., Phyllanthus Linn. emend. Muell.
27 Pandey et al.
Authorship of subsidiary ranks: When a species is splitted into two or more subspecies, one of the resulting subspecies retains the same epithet as that of original species. This is called autonym (self created name). The other subspecies are given different epithets. For example,
Acacia nilotica (L.) Del. ssp. nilotica (autonym)
Acacia nilotica (L.) Del. ssp. indica (Benth.) Brenan.
Other indications: Other indications which may be found appended to scientific name (e.g. “nom illeg.”, “sensu Smith”, etc.) technically do not form the part of author citation, but represent supplementary text. Some specific examples include: z Carex babbii Onley, nom. nud (or nomen nudum) – for a taxon name published without an acceptable description or diagnosis z Lindera Thunb., Nov. Gen. Pl.: 64. 1783, non Adans. – for a homonym – indicating that Thunberg’s Lindera is not the same taxon as that named previously by Adanson. z Betula alba L. 1753, nom. rej. (indicates a rejected) z Ficus exasperata auct. non Vahl – (indicates a misapplied names to a taxon by different authors) z nom. cons. (nomen conservandum) – means a conserved name z nom.nov. (nomen novum) – means a new name z nom. nud. (nomen nudum) – means a name published without a description or diagnosis, making the name invalid z non – means not z orth. cons. (orthographia conservanda) – means a conserved spelling z stat. nov. (status novus) - means a change in rank z vide (video) – means to cite a reference z ! (symbol for vidi, I have seen it) – means a confirmation of name
Legitimacy of names: To be legitimate, a name should not only be effectively and validly published, but should fulfill certain other criteria too. It should be the first validly published name for the taxon, because if there is already a validly published name for the taxon, the second name becomes a superfluous name.
Rejection of names: All names that are not validly and validly published, and lacking typification are rejected. z Superfluous names (new names given to taxa already having legitimate names) are rejected.
28 The Teaching Manual on Plant Taxonomy z Later homonyms (a name spelled exactly like a name previously and validly published for a taxon of same rank) are rejected. Astragalus rhizanthus Boiss. (1843) is a later homonym of Astragalus rhizanthus Royle (1835) and must be rejected. z A tautonym (a name where specific epithet repeats the generic name unaltered) is illegitimate and rejected. e.g. Malus malus, Nasturtium nasturtium. z Nomen nudum ( a name without description). e.g. Quercus dialatata Wall. nom.nud.; Q. floribunda Lindl. ex A. Camus is new/correct name for this species.
Change of names: Changes in names are necessitated due to: i) Detection of illegitimate names, such as tautonyms, later homonyms, etc. ii) Discovery of an earlier valid name. iii) Change in the concept of the taxon, such as merger with the another taxon (reducing to synonymy), or splitting of one taxon in to two (creation of new taxon), raising the rank of a taxon, or transfer of a taxon from one higher taxon to another (new combination).
Other codes
PhyloCode
Some authors encountered problems in using the Linnean system in phylogenetic classification. Since 1998 another Code in development was the PhyloCode, which would regulate what their creators called phylogenetic nomenclature instead of the traditional Linnaean nomenclature (that is, it requires phylogenetic definitions as a “type” attached to every name, and does not contain mandatory ranks). The International Code of Phylogenetic Nomenclature (PhyloCode) is a developing draft for a formal set of rules governing phylogenetic nomenclature. The PhyloCode is associated with the International Society for Phylogenetic Nomenclature (ISPN). Its current version (4b, 2007) is specifically designed to regulate the naming of clades.
Unlike previous, rank-based nomenclatural codes (ICBN, ICZN, ICNB), the PhyloCode does not require the use of ranks, although it does optionally allow their use. The rank-based codes define taxa using a rank (such as genus, family, etc.) and, in many cases, a type specimen or type subtaxon.
In contrast, under phylogenetic nomenclature, the content of taxa are delimited using a definition that is based on phylogeny (i.e., ancestry and descent) and uses specifiers (e.g., species, specimens, apomorphies) to indicate actual organisms. The formula of the definition indicates an ancestor. The defined taxon, is that ancestor and all of its descendants. Thus, the content of a phylogenetically defined taxon relies on a phylogenetic hypothesis.
BioCode
At present there are five codes (ICBN, ICZN, BC, ICNCP and ICTV) having different sets of rules for naming different types of organisms. BioCode is the prospective international rules for the scientific
29 Pandey et al. names of organisms aimed at harmonizing all biological codes. It is basically a synthesis of existing codes.
A more radical approach was made in 1997 when draft of the BioCode has received little attention towards a unified code; the IUBS/IUMS International Committee on Bionomenclature (ICB) presented the long debated Draft BioCode, proposed to replace all existing Codes with an harmonization of them. The originally planned implementation date for the BioCode draft was January 1, 2000, but agreement to replace the existing Codes was not reached. In 2011 a revised BioCode proposed that instead of replacing the existing Codes, it would provide a unified context for them, referring to them when necessary.
30 The Teaching Manual on Plant Taxonomy 5 Taxonomic System of Classification
Introduction
Taxonomic system of classification is a hierarchical arrangement of plant taxa used for classifying the species at different level. In 18th century Carl Linnaeus was the first scientist to develop a hierarchal naming of taxa to denote information on species name and its closest relatives (Fig. 1). After Linnean classification system, many classificatory systems were developed. Globally, there exists tremendous species diversity which cannot be easily studied for understanding their hierarchy. Classificatory systems enable assemblage of taxa into groups on the basis of their similarities and dissimilarities, and there by arranging them at lower hierarchical levels. This chapter includes different classification systems with comparison among some important ones.
Fig. 1. Linnean classification system
Major systems of classification
Of several classificatory systems in use, major ones can be grouped under: Artificial Systems, Natural Systems and Phylogenetic Systems.
Artificial system: also called vertical classification, classifies organisms usually by one or a few characters, irrespective of any relationship amongst them. In comparison to others, this system is easy to handle and convenient to use for identification.
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Natural system: It is also known as horizontal classification or phenetic classification. All known plants are grouped according to the degree of resemblance (similarity or dissimilarity) mainly on morphological features which can be visually examined. The correlated characteristics facilitate classifying the closely related taxa together various hierarchical orders. Several advantages of this system are: (a) plants similar in hereditary constitution are grouped together; (b) a great deal of information is available based on similarity or dissimilarity; (c) new taxon identified can be incorporated into existing system with great ease. One of the best natural systems of classification of George Bentham (1800-1884) and Sir Joseph Dalton Hooker (1817-1911) is even now found most convenient for field identification of plants.
Phylogenetic system: is known as evolutionary classification, as it mainly depends upon evolutionary relationship, or presumed ancestry. It is based on the theory of evolution proposed by Darwin (1859) brought forward the fact that the present-day plants originated from some ancestral ones after undergoing periodical modification. The phylogenetic system by two German botanists, Adolf Engler (1844-1930) and Kari Prantl (1842-1893) was published in their classical work- Die Naturlichen Pflanzenfamilien during the post-evolution era. It includes the modern keys and provides data for identification of all the known genera from the primitive algae to the advanced seed plants.
John Hutchinson (1887-1972) a British botanist considered that the angiosperms have originated from the 'Hypothetical Pro-angiosperms'. The classification of plants was published in his book on: The Families of Flowering Plants in two volumes (Vol. I Dicotyledons in 1926 and Vol. II Monocotyledons) in 1934. Hutchinson made the error of splitting the dicotyledons into two linear evolutionary lines, the Herbaceae and the Lignosae. The system of classification was revised in British Flowering Plants (1948) and again the second edition of the families of flowering plants 1959. He was well-versed in the families of angiosperms all over the world, and therefore his treatments on families were the most informative. Based on the principles of progressive and retrogressive he suggested that all parts of a plant may not be involved in evolution at the same time (Annexure I).
This phyogenetic system is based on the assumption that i) Plants with petals and sepals associated with other floral and anatomical character primitive and more ancient than the plants without sepals. ii) Free floral parts more primitive than the connate (united) parts. iii) Spiral arrangement of floral parts (sepals, petals) and stamens more primitive than cyclic arrangement. iv) Hermaphrodite condition and free stamens primitive over the unisexual flowers and connate stamens. v) A regular or actinomorphic flower to be primitive than zygomorphic flowers. vi) Solitary flower more primitive than the flowers arranged in an inflorescenced.
32 The Teaching Manual on Plant Taxonomy vii) Hypogyny more primitive than epigyny and perigyny conditions. viii) A flower with indefinite number of floral parts primitive over few numbers of floral parts. ix) Complete flower primitive than incomplete flowers.
Some of the merits of Hutchinson’s Classification are: that it is most phylogenetic system of classification based on natural characteristics of plants and is based on evolutionary tendencies and interrelationship among angiospermic plants. Magnoliales representing arborescent plants and Ranales representing herbaceaous plants both show parallel evolution. Reshuffling of genera and families has led to several big orders broken into small orders like Rosales, Paritales, Malveles, Leguminales, etc.; families raised to the rank of orders, Leguminosae family raised to order Malvales/ Leguminales. Origin of monocots from dicots and placement of first dicot and then monocot families is correct in all respect. Gymnosperms were placed before the angiosperms.
Armen Takhtajan’s System based on evidences from all branches of botany (anatomy, embryology, palynology, chromosome number, vegetative and floral morphology, chemical features and geographical distribution) was more phylogenetic than any other system published. However, derivation of the monocots from the Takhtajan’s System was first published as Die Evolution der Angiospermen in 1959. The important features of this system are – (a) Magnoliales s.l is the most primitive group that gave rise to all the branches of angiosperms, and (b) Monocotyledons and Nymphaeales are derived from a hypothetical common dicotyledonous ancestor with vessel-less wood and monocolpate pollen. The angiosperms are considered monophyletic in origin, from primitive fossil orders like Bennettitales. Angiosperms are termed Magnoliophyta, which is classified into classes Magnoliopsida and Liliopsida: Liliopsida or the monocots are derived from the Nymphaeales. Amentifera is considered to be an advanced group; the naked, unisexual inflorescences are derived from multiwhorled, bisexual flowers and inflorescences. Gymnosperms are not considered.
Families in different systems are provided below:
Bentham and Hooker’s System: This system essentially deals with seed and flowering plants, and around 97,000 species in 202 families are described. It was refined based on the system developed by de Candolle. The seed plants are divided into three major classes- Class I - Dicotyledons, Class II-Gymnosperms, and Class-III- Monocotyledons. Monocotyledons are treated as the most advanced. Each class is further divided into subclasses, each subclass into series, and each series into cohorts; the cohorts include the families. One of the unusual features of this system is the position of the gymnosperms between the Dicotyledons and the monocotyledons. Although the system was more natural than that of the earlier workers like de Candolle, a number of taxa could still not be classified satisfactorily.
Engler and Prantl’s System of classification considered the entire plant kingdom (algae to angiosperms). This system emphasized that the incomplete or unisexual flowers were primitive. In this system the angiosperms were treated as a division – Angiospermae – divided into classes –
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Monocotyledonae and Dicotyledonae. Monocots treated as primitive. The Class Monocotyledonae includes 11 orders, some of which are further divided into subordes and families. The class Dicotyledonae was divided into orders and families. The Gymnospermae were placed before the monocots and were presumed to be the progenitor of the catkin-bearing Amentiferae. Angiosperms were considered to be polyphyletic; derived from seed ferns as well as gymnosperms through Amentiferae. Although intended otherwise, the system proved to be more natural and less phylogenetic. Interpretation of simple unisexual flowers (Amentiferae) as primitive is one of the main demerits. Refer to Annexure II for comparison between two major classificatory systems.
Classification system developed by Dahlgren was a modification of Takhtajan’s System and mainly concerned with angiosperms. An imaginary phylogenetic shrub in transaction has been prepared to show the placement of different orders in accordance to their “closeness” to each other. Angiosperms were considered monophyletic in origin because the combination of important features. Like Takhtajan’s System of Classification, it took support from different branches of botany to make this system both natural and phylogenetic one.
Conclusions
An ideal classificatory system should reflect evolutionary relationships by highlighting all the merits of different systems proposed so far. Presently none of the classificatory system is ideal. As a result of new developments and improved techniques in science, species are being reevaluated for re- assessment for the newer classificatory system.
An ideal classification system should be able to address the issues pertaining to: (a) primitive and advanced features, (b) interrelationships between different taxa (at species, genera, families and orders level) based on evidences (on vegetative features; reproductive, anatomy, embryology, cytology, reproductive biology, chemotaxonomy, biochemistry, physiology, cell and molecular biology, histochemistry, ultrastructure, numerical taxonomy) and other inter-related fields (computer taxonomy, ecology and eco-geography). The major goal of taxonomic studies is to develop a truly phylogenetic classificatory system. With further progress in our knowledge on taxonomy of plants this ideal system is likely to be developed.
34 The Teaching Manual on Plant Taxonomy
Annexure I
24 points* covered in the Hutchinson's classification:
1. The evolution is both upward and downward, the former tending towards preservation and the later to their reduction and degeneration of characters.
2. Evolution does not necessarily involve organs at one time or simultaneously.
3. Aquatic plants are derived from terrestrial and saprophytes, parasites, epiphytes are more recent.
4. Trees and shrubs are more primitive than herbs.
5. Perennials are more primitive than biennials and annuals.
6. Plants with vascular bundles arranged in a ring are more primitive those in which vascular bundles are scattered.
7. Spiral phyllotaxy is primitive than whorled and opposite phyllotaxy.
8. Dioecious plants are more advanced than bisexual flowers.
9. Unisexual flowers are more primitive than bisexual flowers.
10. Petalled flowers are more primitive than apetalous flowers.
11. Gamopetalae is more advanced than polypetalae.
12. Zygomorphic flowers are more advanced than actinomorphic flowers.
13. Hypogyny is more primitive than perigyny and epigyny.
14. Simple leaves are more primitive than compound leaves.
15. Solitary flower is more primitive than inflorescenced flowers.
16. Spirally imbricate floral parts are more primitive than whorled and valvate arrangement.
17. Apocarpy is more primitive than syncarpy.
18. Polycarpy precedes oligocarpy.
19. Endospermic seeds with small embryo are more primitive than non endospermic seeds with large embryo.
20. Flowers with numerous stamens are more primitive than those with fewer stamens.
21. Free stamens precede the fused ones.
22. Aggregate fruits are more evolved than single fruit and capsule preceedes berry or drupe.
23. Parietal placentation is more primitive than axial and free central placentation.
24. Trees or arboreal habit are more primitive than climbers are twiners in any one family or genus.
*Source: http://www.preservearticles.com/botany/hutchinsons-system-classification/64
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Annexure II
Comparison of Bentham & Hooker and Engler & Prantl’s System of Classification
Bentham & Hooker Engler & Prantl’s 1. This system is a natural one and is based on several 1. This system is phylogenetic and is based on the idea common and constant natural characters of the plant. of evolution from less specialized to more specialized groups in ascending order. 2. Spermatophytes (seed plants) are classified into 2. Spermatophytes are divided into gymnosperms and dicotyledons, gymnosperms and monocotyledons. The angiosperms. The origin of angiosperms is from origin of angiosperms is not established and position hypothetical gymnosperms like coniferales. The of a gymnosperm is anomalous. position of gymnosperms in not anomalous. Angiosperms are considered to be polyphyletic. 3. Dicotyledons are placed before monocotyledons and 3. Monocotyledons are placed first as they are thought probably dicotyledons were considered to be more to be more primitive than the dicotyledons. The primitive than monocotyledons. In all 202 families are evolutions of dicots and monocots have taken place recognized. parallel from hypothetical gymnosperms. In all 303 families in 55 orders are recognized. 4. Monocotyledons are divided into 7 series beginning 4. Monocotyledons are divided into 12 series beginning with Microspermeae and ending in Glumaceae with Pandanales and ending in Microspermae. 5. Arborous and herbaceous habit are not considered 5. like Bentham & Hooker’s system. as important in the classification of angiosperms. 6. This system is slight modification of de Condolle’s 6. This system is based on Eichler’s system of system of classification. classification. 7. The work of Bentham and Hooker was published in 7. The work of Engler and Prantl was published in "Die "Genera Plantarum". Naturilichen Pflanzenfamilien".
36 The Teaching Manual on Plant Taxonomy 6 Biosystematic Studies on Plant Taxa
Introduction
In the Indian gene centre some of the major crops like brinjal, cucumber, melon, sesame, okra, etc. and their crop wild relatives (CWR) have unresolved issues on the origin and diversity. Issues on identity with respect to allied/related species can be resolved using evidences from morphology, cytology, cytogenetics, and molecular tools. Tools such as predictive characterization models can facilitate in better understanding of useful diversity in genetic resources programme including issues relating to origin and diversity through use of biosystematics.
Term ‘Biosystematics’ deals with evaluation of phenotypic expression taking evidences from fields of morphology, ecology and phytogeography, supplemented from cytogenetics and cytotaxonomy and using new approaches on molecular evolution of genes in determining the taxonomic hierarchy. The term was first coined as ‘Biosystematy’ (by Camp and Gilly 1951) which later changed to Biosystematics. Biosystematics in a broader sense covers “the study of biodiversity and its origins”.
In taxonomic literature, besides the term ‘Biosystematics’, ‘Taxonomy’ and ‘Systematics’ are invariably and interchangeably used. These two terms use data from morphological, behavioural, genetical, and the biochemical observation and use modern tools. Taxonomy mainly differs from the systematics in the classification and naming of organisms whereas the latter deals with determination of evolutionary relationships among taxa (some believe taxonomy as a subset of systematics). These can help in resolving nomenclatural disputes and delimitation of taxa by establishing relationship among domesticated and wild taxa.
This chapter discusses brief about the Biosystematics, Taxonomy and Systematics. The systematics study of selected taxa- Allium (representing diversity rich region) and Trichosanthes, Luffa and leafy Amaranthus (taxa with Indian centre of origin and diversity) were taken up with primarily data from field/ herbarium study and experimental work undertaken at ICAR-NBPGR.
Biosystematics study on selected taxa
Since the inception of the ICAR-NBPGR, biosystematics work has always been a high priority more particularly during 1980s when taxa like Asiatic Vigna, Macrotyloma, and other legumes were collected and studied. Sub-project on “Biosystematics of the genera Vigna, Cucumis, Abelmoschus” undertaken by ICAR-NBPGR [in collaboration with Shivaji University, Kolhapur, North Eastern Hill University, Shillong (NEHU) under National Agricultural Innovative Project (NAIP)] with prime objective to resolve issues on the lines of biosystematics using tools such as micro-morphology, crossability study, wide hybridization, conservation of wide crosses, meiotic study in inter-specific hybrids, molecular cytology and molecular taxonomy was completed.
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of acc.
Fig. 1. Activities in biosystematics studies on taxa of PGR
38 The Teaching Manual on Plant Taxonomy
During 2009-18 some of the prioritised taxa i.e. Allium, Trichosanthes, Amaranthus and Luffa were studied through field, experimental and herbarium work under the institute project (Box 1):
Box 1: Objectives of the Systematics Study
z Delineate taxon boundaries, update on taxonomic status and ecogeography of wild and cultivated taxa
z Trace the morphological relationship among various taxa with an emphasis to closest relatives of cultivated taxa
z Develop field diagnostic keys (mainly using characters of fruit, seed and vegetative parts) for species identification and use by the PGR personnel.
Samples of populations belonging to the same taxonomic category (species, sub-species) from different environments were grown in a common experimental plot/controlled environmental conditions. Selection of taxa depends on level of priority to which a crop may fall in national priority and research priority; however the rare/threatened and endemic taxa always attain top priority. In Trichosanthes in addition to rich species diversity there are identity and nomenclature-related issues. In Allium wild taxa related to cultivated and less-known useful types were takenup. Field and herbarium studies were undertaken and characters were recorded during explorations in areas of availability of the species. Botanical notes were taken in the prescribed format, covering details on herbarium no., collector no., place and date of collection along with remarks. Usually ten plants were used to record data in field/on-site; additionally 3-5 herbarium specimens were collected. Taxonomically good characters were noted especially for micro-characters (bulb membrane, pattern of flower opening, colour, shape of tepals and stamens) in Allium and characters of probract, sepal, fruit and seed in Trichosanthes, flower and seed in Amaranthus and flower, pericarp, seed, fibre and fruit of Luffa.
Need-based herbarium studies were undertaken to understand character variation with respect to ecogeography and distribution range. Rare/endangered species (e.g. Allium gilgiticum), not observed from area of distribution was studied from herbarium material). The images of seed morphology were captured using Image Analyzer; in some cases where the seed coat morphology did not show clear distinction on pattern of testa, the scanning electron microscopic images were taken (300dpi). The vouchers of field collected and experimental material were prepared as herbarium specimens and deposited in recognized herbaria such as NHCP.
Case study
Allium
Genus Allium represents tremendous genetic diversity in the Indian region. Of about 35-40 species reported from the Indian region, species diversity concentrated in alpine and temperate zones of Himalaya. Wild taxa of Allium occur as a part of natural flora, as less-known wild species and sporadic cultivation in backyards. Utility of wild species as donors of genes to widen the base of crop plants has earned wide acceptability. Accomplishment of interspecific crosses between Allium ancepa and A. roylei (an Indian wild species) has indicated the possibility of achieving this goal. Transferring
39 Pandey et al. resistance trait from A. roylei to A. cepa for powdery mildew (Peronospora destructor) and for leaf blight (Botrytis squamosa) (de Vries et al. 1992) has opened new avenue for using the Indian species.
A. atrosanguineum subsp. atrosanguineum, A. atrosanguineum subsp. fedtschenkoanum, and A. semenovii have been prioritized as they are distant relatives of the cultivated Allium (onion and garlic). A. roylei (a wild species that belongs to different subgenus) has been used in onion breeding and shares similarity with cultivated onion based on molecular analysis needs further study. Also many wild Allium taxa under protected habitats or grown in home gardens (in Indian Himalaya) without much changes in characters from the wild types need to be studied for change in character(s) under domestication.
Flower characters were compared among newly collected variants of A. tuberosum (from Leh, Jammu & Kashmir) and accessions collected earlier from north-eastern hill region and western Himalaya (Uttarakhand). Preliminary studies showed that pink flowered form from Jammu & Kashmir was apparently similar to white flowered forms. Phylogenetic and molecular evolutionary analyses have confirmed that Allium tuberosum is distinct from A. ramosum (EC328498) on the basis of sequence of ITS region amplification. Field identification key was developed for Indian alliums for sect. Cepa and Bromatorrhiza. Species of subg. Amerallium, sec. Bromatorrhiza - A. hookeri, A. fasciculatum, A. wallichi and A. macranthum were well distinguishable based on bulb and root characters. Allium hookeri (two variants) were studied for selected characters in field genebank at Bhowali showed variability in plant height, leaf and inflorescence characters. Endemic species of Allium viz. A. kachrooi, A. rosenbachianum and A. oreoprasum, and A. farctum Wendelbo, and A. rhabdotum were studied using herbarium specimens at University of Kashmir, Srinagar. Distinct identity of Himalayan species, often confused/merged with allied ones such as A. przewalskianum Regel (vs A. stoliczkii Regel), A. fedshenkoanum Regel (vs. A. semenovii Regel), A. prattii C.H.Wright (vs. A. victorialis L.) and A. fasciculatum Rendle (vs. A. hookeri Thwaites) was confirmed through this study. While characters such as tunic texture, leaf cross-section and filament vs tepal length are important to distinguish subg. Cepa from other subgenera where as bulb shape, leaf vs scape length, nature of scape (hollow/ solid), tunic colour, presence of bulbils and perianth colour are useful in delimiting taxa within it. Molecular systematic study confirmed the distinctly-shaped (clavate) onion (locally called ‘dunna’), cultivated sporadically in Himalaya and NEH region as one of morpho-types of A. cepa var. aggregatum, (aggregate onion/bunching onion) based on matK sequences.
Assessment of diversity: Western Himalaya recorded maximum concentration (over 85%) of wild species followed by the Eastern Himalaya (6%); others from both the regions (9%). Vertical distribution of species was more confined to the alpine-sub-temperate region (2500-4500m; 29 species), followed by subalpine-alpine region (4500m and above; 5 species) and temperate region (1500-2500m; 4 species). A. fasciculatum and A. stracheyi were confirmed as species under domestication. Based on diversity and availability of material in the field genebank, priority uncollected diversity was worked out. A set of newly collected materials was maintained at field genebank by the ICAR-NBPGR RS Bhowali. During study a total of 31 accessions (7 taxa) from field collected material were raised in experimental conditions at Delhi and Bhowali.
Field and herbarium study: live material maintained in the field genebank at Bhowali and raised in experimental area in ICAR-NBPGR, New Delhi were used for study of vegetative and reproductive morphological traits. Observations were recorded through IPGRI descriptor list for vegetative and
40 The Teaching Manual on Plant Taxonomy flowering details: bulb (shape, size), membrane (colour), leaf (in section), scape (hollow/ round, angular), flower (anther structure), odour (onion like-/ garlic-like) and seed characters (shape, surface). Morphological study and grow-out of aerial bulbils of an unidentified Allium species collected from Himachal Pradesh, which was initially confused with unreported species from India (A. vineale) was identified as Allium ampeloprasum.
Herbarium based work involved study of over 400 herbarium specimens (800 digital scans) mainly housed in herbaria of Botanical Survey of India (Dehradun and Shillong) and Forest Research Institute (Dehradun). Some of the neglected key characters studied included- plant odour (mild, strong, onion/garlic type), bulb membrane (texture), length of pseudo-stem, pattern of flower opening in an inflorescence, stamen character (filament toothed/not toothed) and seed testa characters.
Seed morphological study: Seed morphological study was done in 31 samples (20 taxa maintained in the NHCP) testa. Seeds were studied for micro-morphological characters (seed structure, size, shape, ornamentation of testa, etc.) and seed shape. The images of seed morphology (11 species) were captured using Image Analyzer. Seeds of wild species were black-coloured, width ranging from 1 mm [(A. tuberosum (IC353524; A. carolinianum VDV/AK/37)] to 3 mm. A. fistulosum (IC353547) had the smallest, and A. tuberosum (IC353524) and A. ramosum (EC328498) had the largest sized seeds. As compared to seed shape, seed coat pattern was more variable (convex, granulate, verrucose). Seeds of A. victorialis and A. carolinianum could be identified on the basis of seed shape (using hand lens), while that of A. stracheyi, A. roylei, A. ramosum and A. tuberosum needed use of microscopic aids (high resolution images) for delineating their identity.
Developing identification key: identification key was prepared based on characters- bulb, leaves, scape and spathe characters, shape/size and compactness of inflorescence, structure of capsules, seed/seedlings and quality traits as taste/odour, flower fragrance, etc. (Appendix 1). These keys included characters over and above given in the available floras/ taxonomic treatise/published literature.
Trichosanthes
Field study: explorations/field-trips were carried out across the country viz. parts of Madhya Pradesh, Uttar Pradesh, Western Ghats, Odisha, Eastern Himalaya, Manipur and Meghalaya in order to understand the diversity in Trichosanthes in native habitat across diverse area of distribution of various species and to collect germplasm for study/conservation. Field notes such as place of collection and habitat particulars, habit, sexual condition and those characters lost on drying of herbarium specimens were recorded. About 200 herbarium material augmented during the study were submitted to NHCP. Accessions showing interesting/unique traits were further grown to corroborate the findings.
Augmentation of material and experimental study: accessions augmented/collected during field study and also through various sources such as genebank collections at national and regional level formed the material for study at ICAR-NBPGR, New Delhi (in pots) and at ICAR-NBPGR Base Centre, Cuttack (in experimental field). About 5-10 plants/accession were maintained and observations were taken on 65 characters (using a number of character states; Appendix II).
41 Pandey et al.
Herbarium study: herbarium study involved about 1,200 specimens from NHCP, Central National Herbarium, Kolkata and two Regional Centres Botanical Survey of India (Dehradun and Shillong), Forest Research Institute (Dehradun) and North-Eastern Hill University (Shillong). In addition, on-line digital herbarium of Royal Botanic Gardens, Kew (K), Royal Botanic Gardens, Edinburgh (E), Chinese Academy of Sciences Herbarium (PE), muséum national d’histoire naturelle, Paris (P); and of type specimens were also consulted.
Distinguishing two forms of Trichosanthes bracteata, and distribution of T. himalensis in Eastern Ghats of Andhra Pradesh, were first time recorded during field study of the region. Herbarium studies revealed that the specimen (M.S. Ramaswami 1398), claiming the presence of Gymnopetalum chinense in Andhra Pradesh, turned out to be Solena; also studies indicated the probable occurrence of (true) T. tricuspidata in Andaman Nicobar Islands. Type specimen (in Kew and Harvard Herbarium) study revealed that the type (male and female specimens) of T. khasiana in fact represent two different species (T. khasiana and an unknown species), and confirmed the occurrence of T. subrosea in India. Infrageneric classification of 16 Indian species at subgeneric and sectional level was worked out.
Field study of Eastern Himalayan endemic species T. dicoelosperma C.B.Clarke was carried out; this possesses red pulp (akin to snake gourd) and seeds are tridentate on distal end (central one prominent). Herbarium studies indicated the extended distribution of T. cucumerina L. subsp. sublobata (Kundu) K.Pradheep, D.R.Pani & K.C.Bhatt in Gujarat and T. cordata Roxb. in terai region of Upper Gangetic Plains. Analyses of the rbcL sequence amplified in 71 accessions comprising of three species of Trichosanthes (T. cucumerina, T. dioica and T. nervifolia) and two species of Gymnopetalum (G. chinense and G. wightii) revealed that this locus has grouped almost all the accessions as per the species they belong to.
Outcome of the work suggested modification in the key in the light of observations recorded and knowledge generated in the range of some continuous characters and overlooked underestimated or misinterpreted characters. Identification keys were developed for valid taxa using all the information obtained from above studies; spot-characters enabling quick identification of various species in field are given (Appendix 2). Four taxa have been recognised as accepted ones namely T. cucumerina L. subsp. cucumerina (syn. T. lobata Roxb.); T. cucumerina L. subsp. cucumerina ‘Anguina’ (L.) K.Pradheep, D.R.Pani & K.C.Bhatt; T. cucumerina L. subsp. villosula (Cogn.) K.Pradheep, D.R.Pani & K.C.Bhatt (syn. T. perrottetiana Cogn.); T. cucumerina L. subsp. sublobata (Kundu) K.Pradheep, D.R.Pani & K.C.Bhatt; and their diagnostic keys worked out.
Amaranthus
Gap analysis revealed nil collection of wild species - Amaranthus polygonoides, A. x caturus, A. tenuifolius and different subspecies of A. graecizans, and poor representation of A. graecizans subsp. graecizans, A. blitum and A. dubius indicating the need for proper collection and identification. A. graecizans (4 accn.) and A. blitum (8) have been studied in detail; in A. blitum, characters like sub-erect plant habit and retuse leaf were observed to be stable, whereas ‘lanceolate’ bract shape as reported was validated as ‘linear’ in all the accessions. Study of types of intended taxa in virtual herbaria revealed high level of variation in A. tricolor complex. Molecular systematics supported these findings using 50 SSR primer pairs and optimizing amplification conditions at 36 loci in 60 accessions.
42 The Teaching Manual on Plant Taxonomy
Field studies revealed variation among cultivated and wild/weedy types in A. graecizans L. (in Rajasthan), A. tricolor L. (in Tamil Nadu and Jharkhand) and A. dubius Mart. & Thell. (in Jharkhand and Arunachal Pradesh); fast spread of A. palmeri S.Watson in North India were recorded. Amaranthus blitum, A. dubius, A. tricolor, A. graecizans and A. powellii were augmented from Assam, Jammu & Kashmir, Kerala, Nagaland and Tamil Nadu.
Experimental study: in A. tricolor complex (86 acc.) revealed some mistaken taxonomic identity in about one third of the studied material. Micro-morphological study for selected characters in this complex identified some stable characters (branching pattern of lower stem, length of petiole vs lamina, leaf shape) and some linked characters. Diagnostic characters- bract vs tepal length, bract shape, tepal shape, branching of terminal inflorescence and filament length were unreliable. Amaranthus tricolor var. tristis is traditionally distinguished from var. tricolor by branching from base of stem (vs branching above middle). Besides A. tricolor var. tristis is further different from the typical variety by stem being yellowish-green, petiole as long as lamina, leaves ovate with subcordate to obtuse base. A. mangostanus, presently subsumed under A. tricolor, deserves distinct identity at infraspecific level due to semi-perennial, decumbent-ascending habit, rooting at nodes, small rhombic- ovate leaves.
Herbarium study: studies made in Botanical Survey of India (PBL, Port Blair; MH, Coimbatore) and PCM, Chennai and Rapinat Herbarium, Trichy with an emphasis on differences between wild and cultivated forms of A. tricolor and spiny nature of Amaranthus spinosus from different habitats. Study of type specimen revealed that A. parganensis Saubhik Das and A. bengalensis Saubhik Das & Iamonico are not sufficiently distinct from A. tricolor var. tricolor and A. mangostanus, respectively. Good taxonomic /field characters were identified for all taxa in leafy amaranth. Study helped in understanding the distribution of unfamiliar taxa A. polygonoides L., A. tenuifolius Willd., A. x caturus B.Heyne ex Hook.f. was worked out. Meagre herbarium holdings of A. dubius indicated recent naturalisation of this weedy species in the country, supported by its exclusion in past floristic literature.
Luffa
Field study: experimental study undertaken using 48 accessions (all 5 taxa) revealed that 18 out of 44 characters were of taxonomic value- leaf pubescence, stem angularity, probract shape, sex form, flower bud shape, flower colour, time of flower opening, calyx and petal colour, stamen shape (anther -thecae), stigma length (vs stamen), fruit surface, fruit distal tip, flesh colour, sponge/fibre texture and seed shape, colour and surface. Some linked characters identified were: fruit ridges and seed surface (in L. acutangula); pericarp fibre netting pattern in wild vs cultivated taxa; and fruit shape and seed orientation. At infraspecific level, leaf shape, flower opening time, flower colour, stamen shape and fruit/seed surface were found to be important for identification.
In contrast to usual treatment of L. hermaphrodita Singh & Bhandari under L. acutangula (L.) Roxb. (on the basis of crossability and molecular evidences), there is need to place this cultigen infra-specifically under ridge gourd owing to distinguishing characters such as short plant stature, earliness, bisexuality, small and less-fleshy fruit, loose fibre and smaller seeds. Grouping was evident based on data on fruit and seed characters in L. acutangula and a closely related cluster-fruit bearing L. hermaphrodita and also its solitary-fruited type. Luffa acutangula var. amara from Uttarakhand
43 Pandey et al. and Rajasthan showed variation among fruit and seed characters especially mosaic pattern. In L. echinata characters studied in material from Haryana and Uttarakhand and plants grown under experimental conditions showed good variation.
Experimental study: gap analysis revealed the need for augmenting germplasm of wild Luffa collections in L. echinata and L. graveolens across the distribution range especially north and eastern India (Bihar, Uttar Pradesh and parts of Madhya Pradesh). Poor growth of Luffa hermaphrodita (no healthy fruit formation), and L. graveolens in Delhi conditions indicated habitat specificity.
Herbarium study: revealed the occurrence of L. echinata Roxb. in Andhra Pradesh, and the rare status of L. graveolens Roxb. Luffa echinata studied in herbarium revealed that var. echinata as much variable in shape and size of fruit as well as echines on pericarp; var. longistylis (only available in K) only as type was not available in India.
Conclusions
Biosystematics studies from PGR point of view can help in resolving issues on identity and nomenclature. Based on prioritization, focus is currently on collection/study of not-yet-collected/niche- specific species, material and employing cytological and molecular tools to validate the research results was emphasised. Micro-morphological investigation for seed coat texture, trichome, epidermal and pollen characters and other often neglected traits needed study to correlate the status among the related groups.
44 The Teaching Manual on Plant Taxonomy
Appendix I
Key vegetative and reproductive characters used for study of different species of Allium
S. No. Plant part Character(s)
1. Storage organ bulb, rhizomes, swollen roots (shape, size, longitudinal/ transverse section) 2. Bulb well developed, single/ clustered, shape (cylindrical, oval, etc.), size, bulb colour, texture of outer covering (membranous, fibrous), bulblets (if present exterior to the main bulb); not developed (A. hookeri, A. fasciculatum) 3. Roots normal, swollen (storage roots) 4. Pseudo-stem if well developed (length, diameter) 5. Leaf fistular/ flat, erectness; flat leaves not folded length wise (A. tuberosum), keeled (A. ampeloprasum, leek); fistular (circular outline in section; triquetrous in section) 6. Scape enclosed in bulb, shorter or equal to, longer than pseudo-stem, tapering at tip, straight/ coiled, hollow/ solid (full or partly) 7. Inflorescence spathe size (LxB), shape (globular, oval, elliptical), tailed when in bud, if persistent; size of the inflorescence, number of flowers, compactness 8. Bulbils presence of bulbils (aerial/underground) 9. Flower size, colour, shape of flower when completely opened 10. Perianth shape, colour / markings 11. Stamens equal/ unequal sized, exserted/ not exserted, anthers and filament colour, position in relation to stigma 12. Pistil tip, colour, shape/ size, etc. 13. Fruit capsule with or without persistent spathe 14. Seed colour, shape, size (LXB), seeds coat texture (rough/ shiny), 100 seed weight 15. Seedling cotyledonary leaf, if coiled Other characters 16. Anatomy of leaf structure of mesophyll cells and stomata, stomata index 17. Pollen shape (oblate, super-oblate, elliptical), ornamentation 18. Odour garlic or onion type (strong/lighter odour)
45 Pandey et al.
Appendix II
Spot characters for field-level identification of some taxa of Trichosanthes
Trichosanthes z Male flower solitary z White fringed flowers (night flowering) z Fruit yellow-orange z Smooth & red fruits (round to oblong) z Seed round T. cucumerina subsp. cucumerina T. bracteata (syn. T. palmata) z Occur in disturbed areas z Frequent z Annual climber z Liana z Leaves soft, 3-7 lobed z Leaves scabrous z No probracts, bracts z Bracts large ovate z Fruits ovate-oblong, white striped z Calyx entire/dentate z Seed edges toothed z Fruits round-ovate
T. cucumerina subsp. cucumerina ‘Anguina’ z Seeds marginated z Cultigen T. majuscula z Plant parts- larger (than subsp. cucumerina) z Forests in north eastern India, deeply lobed, membranous z Prominent peduncle merging with snake like fruits z Leaves big T. himalensis z Calyx segments entire z Mid-hill forests of north eastern India z Fruits always oblong z Perennial, tuberous-rooted z Seed with raised central line, ± angular z Leaves shiny, rarely lobed T. truncata z Probract absent, bract small z Mid-hill forests in north-eastern India z Seed turgid, drum-shaped z Liana along with Hodgsonia T. dioica z Leaves entire, glabrous, ovate, 3-prominent nerved z Cultigen z Fruit big, round-oblong, greenish yellow at maturity z Dioecious z Seed 2 x 1.2 cm z Leaves scabrous
46 The Teaching Manual on Plant Taxonomy 7 Modern Tools in Plant Taxonomy
Introduction
Modern approaches in plant taxonomy provide a better understanding of evolutionary processes, and delimitation of species particularly in some taxonomic complex groups. One of the advantages of molecular techniques for plant taxonomy is that analysis can be performed at early developmental stages, from living plant material as well as from voucher herbarium specimens. This allows an “integrative” approach combining modern molecular data with taxonomic description of reference species. Data from other advanced fields such as serology, phytochemistry, cytology and molecular science along with morphological data are proving important in interpreting taxonomy of the plants. It may be useful in understanding phylogenetic relationships, especially considering that species of some genera are not easily identified. Similarly ease of use of the chemotaxonomic tools has gained popularity especially in resolving the identity issues. This chapter deals with some of the non-traditional modern tools-serotaxonomy, chemotaxonomy, cytotaxonomy and molecular taxonomy in dealing with plant taxonomy issues.
Serotaxonomy
Serology deals with interactions of antigenic material and antibodies. When foreign cells or particles (antigens) are introduced into an organism, antibodies are produced in the blood (antiserum). Proteins most widely used as antigens in serotaxonomy are those, which carry useful taxonomic information and are easy to handle. Both structural and reserve proteins (mostly the storage and pollen proteins) belonging to same group can be used in systematics interpretation. Phytoserology, which deals with immunochemical reactions, between serum antibodies and antigens, has also established itself as a valid method in systematics, because it helps to detect homologous proteins. Nuttall was the first biologist to compare the immunochemical specificity of serum proteins for systematic purposes. Kowarski, Bertarelli and Magnus were the other early notable serologists, who compared proteins from various grass and legume species, showing similarities and differences.
Serotaxonomy methods
In this method, a crude protein extract of a particular plant taxa (antigen) is injected into the blood stream of an experimental animal, usually a rabbit or a rat, to develop antibodies. In response to the specific antigen injected, a specific antibody is produced in the blood of the animal. The serum (termed the antiserum) containing the antibody is then collected and made to react in vitro with the antigenic proteins as well as proteins from other related taxa, of which the affinities are in question.
Serological reactions between antibodies and antigenic material form of a precipitate and degree of protein homology is determined by the amount of precipitation and hence is taken as a phylogenetic marker and taxonomic character. Crude protein extracts have the limitation in their specificity and reactivity due to large number of proteins stimulated through range of antibodies.
47 Pandey et al.
A novel method of pre-absorption i.e., an antibody system induced by immunization with a crude protein extract (the antigen system) of one species is ‘pre-absorbed’ by the antigen system of a second species and then tested with the antigen systems of other species. The recent development of powerful analytical techniques and instrumentation has facilitated use of monoclonal antibodies (single kinds or species of antibody directed against single epitopes). a. Immuno-diffusion in Agarose Gels: this method includes antigen-antibody reaction in gels, mostly of agarose, in petri dishes. The antiserum containing antibodies is filled in a well at the centre of the gel and the antigens from related taxa are placed in outer or radial wells. The antigen and antibody react to produce the insoluble antigen-antibody complex, forming a thin immobile band of precipitin (protein) at equilibrium, which can be visualized either directly or after protein staining for interpretation. There are two basic methods: i. Single radial immunodiffusion method (antigen is allowed to diffuse into the gel containing the antiserum); and ii. Ouchterlony (double immunodiffusion method (both the antigen and antibody are allowed to diffuse into the gel and meet each other). b. Rocket Immunoelectrophoresis: in this method in which, rocket-like immunoprecipitate is formed when the desired protein (antigen) is electrophoresed in an agarose gel containing its mono-specific antiserum. A comparison of the height of the peaks of the unknown and standard samples also allows the unknown protein concentration to be determined. c. Enzyme-Linked Immunosorbant Assay (ELISA): ELISA is used for quantitative estimation of a particular protein in a mixture, but can also be used to study the antigen-antibody reaction. The antibodies against a particular antigen are adsorbed to a solid support, in most cases a polystyrene micro titer plate. The support after coating with antibody is washed and then the antigen is added, which binds to the adsorbed antibodies. An enzyme-linked antibody molecule called the conjugate is then added, which also binds to the antigen, which is followed by a chromogenic substrate for the enzyme. The colored product generated is observed for confirmation of antigen-antibody reaction as well as measured for quantitative estimation. Intensity of the colour is proportional to the bound enzyme and thus to the amount of the bound antigen.
Cytotaxonomy
When cytological evidences are utilized for delineating the two taxa, it is called as cytotaxonomy. Chromosome number is the karyotype feature most commonly used in cytotaxonomical analyses. The chromosome number can be a plesiomorphic characteristic of a large clade or a recurrent trait which arose independently in two or more clades. Some concepts regarding chromosome number variation, such as base number, aneuploidy, paleopolyploidy, and neopolyploidy have been used by different authors in quite different ways. Therefore, these concepts in cytotaxonomy and karyotype evolution deserves much attention.
Chromosome number: diversity of chromosome numbers and their relative constancy within populations and species provide an important character for taxonomic groupings of large number of plants (with some exceptions). These changes usually occur in chromosomes during the process of division, and these changes may affect the gene sequence, their number or even there may be loss of chromosomes themselves. The perpetuation of this slow process, results in the evolution of new
48 The Teaching Manual on Plant Taxonomy chromosomal races. Ophioglossum species (Pteridophyte) has the highest number of chromosomes in the plant kingdom (2n = 1240). i. Constant Number: In certain groups of vascular plants, the chromosome number is constant throughout the whole group, as in Quercus and other members of the Fagaceae have the same basic number, n = 12. In such cases chromosome number is not of relevance in taxonomic significance for taxa within the group. ii. Euploidy: When chromosome numbers in various members of a taxon are in the proportion of exact multiples, the series is described as euploidy. For example in Malvaceae, the somatic numbers in various species range from 10, 15, 20, 25, 40; from 12, 18, 24 to 30; from 14, 28, 42, 56 to 70 and so on.
a. Basic number: In an euploid series, the various members may be unified by a basic number (x) which is the gametic number of a diploid species. As in the above example of Malvaceae, the basic number x = 5. The other species in the series are described as triploids (3x), tetraploids (4x), hexaploids (6x) … polyploids (nx). The basic number is usually constant for a genus or higher taxa and has proved useful in supra-specific studies.
b. Primary and secondary basic numbers: In many cases, more than one basic number can be present in a group. For example, in the living species of Chlorophytum (Liliaceae), the chromosome numbers vary from 14 to 28, 42, 56, 84, etc. and also from 16 to 32, which means that Chlorophytum has two basic numbers x = 7 and x = 8. In such cases, the inferred base numbers ranging between 2 and 13 may be referred to as the primary basic numbers in the absence of living diploid members, while the remaining are termed secondary basic numbers. In case of Chlorophytum however, Naik (1976 ) from his detailed analysis of the meiotic behavior of chromosomes in one of the species, C. laxum, has shown that the two base numbers 7 and 8 should be considered as secondary, most probably derived from the primary basic number x = 4.
c. Polyploid pairs: Closely related species in certain groups of plants may be cytologically distinct i.e., one may be diploid while the other a tetraploid. Such related pairs are termed polyploid pairs. For example, Cardamine hirsuta (2n = 16) and C. flexuosa (2n = 32) of the Brassicaceae is a polyploid pair.
d. Dibasic Polyploidy: It is now a well known fact that hybridization has a dominant role in evolution and such hybridization may involve crossing of any two genetically unlike individuals, which have different base numbers of chromosomes. Such hybrids undergo polyploidy since each chromosome is doubled as the pairing at meiosis is restored, and this type of polyploidy is termed as dibasic polyploidy. An excellent example of this type of polyploidy is artificially synthesized Raphanobrassica, which is a hybrid between Brassica oleracea (2n = 18) and Raphanus sativus (2n = 20) and has 2n = 38 chromosomes. iii. Aneuploidy: If the chromosome numbers in the different members within a group bear no simple numerical relationship to each other, then the series is termed as an aneuploid series or simply aneuploidy. Various species of Carex (Cyperaceae) for example show a wide range of chromosome numbers from n = 6 to 112 with multiples of 5,6, 7, and 8 thus exhibiting aneuploidy.
49 Pandey et al.
Aneuploidy may result due to either of the following:
(i) Change in the basic number: An increase or decrease in the number of chromosomes may take place, whereby the same genetic material becomes distributed in a different number, leading to a change in the basic number. This phenomenon is important from the taxonomic and evolutionary point of view, as change in the basic number results in new variations and recombination’s, leading to the evolution of new varieties and ultimately to new species. The changes in the basic number of chromosomes can be brought about by a process called polysomaly. This is very common and results in increased sets of genes if there is a duplication of one or a pair of chromosomes. This means that any one pair may undergo polyploidy. Due to this some of them can afford to lose one or two chromosomes and get stabilized in nature with this new chromosome number. This naturally brings about a different basic number. For example, most of the species of Dahlia (Asteraceae), have x=8, but D. merckii is regarded as a polyploid, with n= 18, resulting by addition of two pairs of chromosomes.Polyploidy has also been reported in Datura, Nicotiana, etc. Polysomics can be of various types:
a. Trisomies: plants containing one extra chromosome are known as trisomies i.e., 2n + 1. b. Tetrasomics: plants containing two extra chromosomes are known as tetrasomics i.e., 2n + 2, etc. c. Monosomies: plants with one chromosome less are known as monosomies i.e., 2n – 1. Normally diploid monosomies are inviable. d. Nullisomics: plants with two chromosomes less are known as nullisomics i.e., 2n – 2, etc. Polysomics are usually unstable and as they are not isolated genetically from their relatives under natural conditions, they would lose their identity through crossing with normal plants followed by selection for more viable, genetically balanced normal disomic types. ii) Basic number remaining unaltered: The basic number may remain unaltered, but the genetic material present may be changed due to the addition or loss of chromosomes. This phenomenon is less important from the evolutionary point of view as the genetic make-up of a taxon becomes unbalanced due to loss or addition, resulting in an unstable condition, which cannot be perpetuated and thus cannot give rise to well differentiated novelties.
(iii) B-Chromosomes: They are one or more accessory or supernumerary chromosomes, in addition to normal chromosomes and have been detected in a large number of plants. In plants, when compared to the other members of the chromosome complement, they are generally of a much smaller size and are of unknown origin. They reduce fertility or increase the vigour of plants. It has been found that they perpetuate in certain natural populations and may have some evolutionary significance.
Chromosome size: The individual chromosomes of some taxa show marked differences in shape and size at mitotic metaphase. The size of chromosome varies greatly in different families and also amongst members of the same family. The monocotyledons usually have larger chromosomes than the dicotyledons. In general, woody plants have smaller chromosomes than their herbaceous relatives. Chromosome size is not related to the phylogeny of angiosperms in general but is characteristic of only certain groups and families.
50 The Teaching Manual on Plant Taxonomy
Chromosome morphology: Apart from the number and size of the chromosomes in flowering plants, conspicuous differences in appearances of the karyotype of the chromosomes have also been found in species having the same chromosome number. The chromosomes are best discernible at mitotic metaphase. The karyotype of the chromosomes can be characterized on the following basis: a. Relative length of the arms of chromosomes; b. Position of the centromere ; c. Presence of satellites. Accordingly the chromosome symmetry, it can be characterized as:
Symmetrical: A karyotype consisting of chromosomes all essentially similar to each other in size and with median or sub-median centromeres and with two equal arms are termed as a symmetrical chromosomes. Metacentric or V-shaped (Chromosomes with median centromere); (ii) Sub- metacentric or L-shaped (Chromosomes with sub-median centromere). Karyotypes of this nature are the most common ones.
Asymmetrical: this type of karyotype possess many chromosomes with sub-terminal or terminal centromeres, or great differences in size between the largest and the smallest chromosomes, or both. Depending on the position of the centromere they may be of: (i) Acrocentric or J-shaped- Chromosomes with sub-terminal centromere; (ii) Telocentric or I-shaped- Chromosomes with terminal centromere.
Karyotypes of this nature are considered as specialized types. For example, in the advanced genera Aconitum and Delphinium (Ranunculaceae), the flowers have the largest number of J-shaped chromosomes.
III. Secondary constrictions and satellites: Secondary constrictions, which are small bead-like appendages. Occasionally they occur at the terminal ends of one or more pairs of chromosomes in many species and are known as satellites. These structures are widely distributed in the plant kingdom, which shows that they are a valuable, if not essential, part of the chromosomal complement. However, very little is known about the evolutionary changes in the satellites and nucleoli. Generally, the asymmetrical karyotypes are most common in plants, which are usually specialized morphologically, while symmetrical ones are found in more or less generalized plants, but also occur in morphologically specialized ones too. Unequal translocations and inversions involving the centromere seem to be responsible for this.
Chromosome behaviour at meiosis: pairing behaviour at meiosis is mostly determined by chromosome number and chromosome homology.
1. Show whether hybridization has occurred: degree of chromosome homology, in hybrids is an indication of the degree of relationship of the parental species.
2. Indicate structural differences in the parental chromosomes: meiotic pairing behaviour in hybrids can also point to structural differences in the chromosomes of its parents.
a. Translocations- a chromosomal segment is removed from one place and reinserted somewhere else in the genome, either in the same or in some other chromosome.
b. Inversion of segments- a segment of a chromosome becomes reinserted in the same chromosome but the opposite way around.
51 Pandey et al.
It can be further of two types: (i) Paracentric- inversions involving only one chromosomal arm; (ii) Pericentric- inversion incorporating the centromere i.e., involving both chromosomal arms. Ther could be two conditions- Deletions (an interstitial or terminal chromosomal segment is lost) or Duplications (segment of the chromosome is represented two or more times in a chromosome of a homologous pair).
A study of the process of meiosis in hybrids yields information of great evolutionary significance. The fertility of a hybrid depends upon the degree of homology between the chromosomes of its parents. When this process is irregular in hybrids, it results in disharmony between the genetic systems of the parents involved. The more the number of non-homologous segments in the hybrid, the more is the incidence of irregularities, the greater the degree of sterility and greater the magnitude of evolutionary distance between the parents. Thus, whether the hybrid is vigorous or weak, whether it produces viable or in-viable pollen, and whether it is capable of producing greater or lesser amount of seed, helps in estimating the degree of homology of the genomes involved, which ultimately reflects a measure of species relationships i.e., degree of pairing is proportional to the degree of homology of the genomes.
Molecular taxonomy
Genomic approaches makes use of the diversity among DNA sequences to identify organisms. These sequences being embedded in every cell are considered as genetic ‘barcodes’. Barcodes have only four choices of nucleotides at each position but the string of sites is huge. It should show higher level of variation among the species and should be conserved enough to show no variation within the species. The barcode should contain enough phylogenetic information to assign the species to a particular taxonomic group. The region should have highly conserved primer binding sites for the case of amplification and sequencing. The sequence should be short enough to amplify even from degraded DNA. The insertions, deletions and substitutions at nucleotide level of the barcodes are the characteristic of the evolutionary path which makes barcoding technique as a valuable tool to classify even cryptic species. The overall components of the barcoding technology consists of sample to be barcoded, laboratory technique including the use of universal primers to amplify barcodes from the sample and online databases that contains the sequences of standard barcodes most of the species. The success of barcoding depends on the construction of an online library that contains the standard sequences of barcodes of almost all species. The Consortia for Barcode of life (CBOL) has recommended the use of ITS, matK and rbcL as universal barcode loci for land plants.
The internally transcribed spacers (ITS) 700bp long sequence, present in the rRNA genes of all eukaryotes serves as a barcoding region. The ITS 1 and ITS 2 on the either side of 5.8s rRNA gene shows variation at length and nucleotide level which is useful to assign an organism into a specific taxon/family. As ITS 1 and 2 are flanked by conserved rRNA genes universal primers can be synthesized for the amplification in PCR.
The rbcL is present in the chloroplast genome codes for larger sub unit of the enzyme ribulose- 1,5- bisphosphate carboxylase which is an important enzyme in the process of photosynthesis, is used as an universal barcode for land plants. The variation due to substitutions of nucleotides in this gene infers to the amino acid sequence of the enzyme. This characteristic of rbcL gene favours the use of this region in classifying plants. The length of the locus is 1380bp. As a barcode should be
52 The Teaching Manual on Plant Taxonomy short enough for ease of amplification and sequencing, this property of rbcL may be a draw back in the use of barcoding. Even though, the high substation rates and evolutionarily informative sites of this gene makes it as a standard barcode.
The group II intron named trnk (lysine tRNA) codes for the enzyme ‘maturase’ that serves as a putative protein in the RNA splicing process is used as an universal barcode for plants as the maturase activity on splicing depend upon the intron of a particular species, the matk shows variation at molecular level to diverge species.
Molecular taxonomic methods
Materials
1. Authenticate plant materials (group of species of a genus/genera/family) 2. Thermal cycler 3. Electrophoresis unit with power pack 4. Microcentrifuge 5. Micropipettes 6. Micro centrifuge tubes 7. PCR tubes 8. Tips 9. Gloves
Laboratory regents
1. Plant genomic DNA (20-30 ng/ul) 2. PCR reaction components: a. Taq polymerase (5U/ul) (Cat no. TQ252 Geneaid) b. Taq buffer (10X) (Cat no. TQ252 Geneaid) c. dNTP’s (10mM) (Cat no. DN4400 Geneaid) d. Nuclease free water (Cat. No.P1193 Promega) e. PCR primers (custom synthesized Eurofins Bangalore) 3. Electrophoresis reagents a. Agarose (0.8%) (Cat. No.A2132 Biomatik) b. TAE Buffer (50X) (Cat. No. B49 Fermentas) c. Loading dye(1x) (Cat. No.DM010-R500 Biobasic) d. 100 bp DNA ladder (Cat. No.DM010-R500 Biobasic) e. Ethidium bromide (Cat. No. 2512 Biomatik)
4. PCR purification kit (Hipur A Cat.No.MB512 Himedia) 5. DNA sequencing (Eurofins Bangalore)
53 Pandey et al.
PCR and Sequencing primer map for ITS, matK and rbcL loci
trnK570F TCC AAA ATC AAA AGA GCG ATT GG matK80F CTA TAC CCA CTT ATC TTT CGG GAG T matK390F CGA TCT ATT CAT TCA ATA TTT C matK800F CAT GCA TTA TGT TAG ATA TCA AGG matk1200F GAY TCT GAT ATT ATC AAC CGA TTT G matK190R ATT CGA GTA ATT AAA CGT TTT ACA A matK530R GTT CCA ATT CCA ATA CTC GTG AAG matK950R AAA ATM ACA TTG ACA TAA ATT GAC AAM G
ITS1 CTT GGT CAT TTA GAG GAA GTA A ITS2 GCT GCG TTC TTC ATC GAT GC ITS3 GCA TCG ATG AAG AAC GCA GC ITS4 TCC TCC GCT TAT TGA TAT GC
rbcL 1F ATG TCA CCA CAA ACA GAA ACT AAA GC rbcL 560F GTT TAT GAA TGT CTT CGT rbcL 724F GCT ACT GCA GGT ACA TG rbcL 724R CAT GTA CCT GCA GTA GC rbcL 1352R CTT CAC AAG CAG CAG CTA GTT C
Procedures
Composition of PCR amplification mix
S.no Component Volume (μl) 1. Taq polymerase (5U/ul) 0.3 2. Taq buffer (10X) 5
3. Mgcl2 (15mM) 5 4. dNTPs (15mM) 2.5 5. Forward primer (5 pmoles) 1 6. Reverse primer (5 pmoles) 1 7. Template (20-30ng) 2 8. Nuclease free water 33.2 Total 50
54 The Teaching Manual on Plant Taxonomy
PCR amplification condition for ITS
Step 1.Initial denaturation : 94° C for 3 minutes Step 2. Cycle Denaturation : 94° C for 30 seconds Step 3. Annealing : 50° C for 1 minute Step 4. Cycle Extension : 72° C for 1 minute Step 5. Final Extension : 72° C for 5 minutes Step 6. Hold : 4° C for 30 cycles of PCR was carried out from Steps 2 to 4.
PCR amplification condition for matK
Step 1.Initial denaturation : 94° C for 3 minutes Step 2. Cycle Denaturation : 94° C for 30 seconds Step 3. Annealing : 47° C for 1 minute Step 4. Cycle Extension : 74° C for 1 minute Step 5. Final Extension : 74° C for 5 minutes Step 6. Hold : 4° C for 10 minutes 35 cycles were carried out from step 2 to 4.
PCR amplification condition for rbcL
Step 1.Initial denaturation : 94° C for 3 minutes Step 2. Cycle Denaturation : 94° C for 30 seconds Step 3. Annealing : 52° C for 1 minute Step 4. Cycle Extension : 74° C for 2 minutes Step 5. Final Extension : 74° C for 10 minutes Step 6. Hold : 4° C for 10 minutes 35 cycles were carried out from step 2 to 4.
Preparation 0.8% Agarose gel (earlier chapter): Load 5 μl above PCR reaction to check the amplification and determining the purity and size of the amplified fragment for further analysis.
PCR purification (Kit based): DNA is bound on a silica membrane within the spin column. The bound DNA is washed and the clean, concentrated DNA is eluted. This is to be done using Hi Pura (HI MEDIA)PCR purification kit.
1. Add 5 volumes of Binding Solution to 1 volume of the PCR reaction and mix. For example, add 500 μl of Binding Solution to 100 μl of the PCR reaction. Transfer the solution into the binding column.Centrifuge the column at maximum speed (12,000-16,000 Xg) for 1 minute. Discard the eluate, but retain the collection tube.
2. Replace the binding column into the collection tube. Apply 0.5 ml of diluted Wash Solution to the column and centrifuge at maximum speed for 1 minute Discard the eluate, but retain the collection tube.
55 Pandey et al.
3. Replace the column into the collection tube. Centrifuge the column at maximum speed for 2 minutes, without any additional wash solution, to remove excess ethanol. Discard any residual eluate as well as the collection tube.
4. Transfer the column to a fresh 2 ml collection tube. Apply 30 μl of Elution Solution to the center of each column. Incubate at room temperature for 1 minute.
5. To elute the DNA, centrifuge the column at maximum speed for 1 minute. The PCR amplification product is now present in the elute.
The purification product can be further checked by running it on 0.8% Agarose gel and used for sequencing using sequencing primers.
Chemotaxonomy*
Among the modern and advanced sciences, the field of ‘Chemotaxonomy’ in chemistry has served as a good support in classification of plants on the basis structure of the secondary metabolites. This is based on the concept of specificity of chemical structure of the secondary metabolites and biosynthetic pathways that has led to resolving taxonomic issues. Chemotaxonomic methods are useful to taxonomist, phytochemists and pharmacologists to resolve issues of identity and phylogeny. Chemotaxonomy involves the study of chemical variation at a level of genera/species/subspecies in plants including microorganisms. It is a useful tool for the investigation of distribution of chemical compounds or groups of biosynthetically related compounds in related genera. In plants primary metabolites (amino acids, fatty acids, oligosaccharides and organic acids) provides insight for distinguishing at genera/species level where as secondary metabolites such as phenols/flavones, essential oils provides more specific details. These methods are efficient, and flexibile to use form plant parts in fresh, dried or crushed form. Chemotaxonomic methods are more popular for analysis and interpretation of data for medicinal and aromatic plants as compared to the other group such as food plants. In angiosperm families- Malvaceae, Ranunculaceae, Magnoliaceae, Polygonaceae and Solanaceae chemotaxonomic methods have been used. In medicinal plants ‘Chemotypes’ were identified based on different sets of secondary metabolites. This difference must be consistent in changing environment and heritable. Seeds of cowpea are rich in caffeic acids, chlorogenic acid, daidzein and genistein which is absent in green gram while green gram has vanillic acid, apigenin, kaempferol and isorhamnetin which is absent in cowpea (Longvah et al. 2017). Pulse crops viz. mothbean, cowpea, blackgram, greengram and rice bean can be distinguished chemically on the basis of primary metabolites. On the basis of analysis of secondary metabolites viz. profile of phenols there is a clear distinction observed between cowpea and green gram. The taxonomy of aromatic plants of different genera from diverse geographical locations is complicated among species, varieties and cultivars without significant differences in morphology. Taxonomic identification of basil/Ocimum spp. and lemon grass/Cymbopogon spp. are linked to their chemical constituents; essential oil composition at inter and intra species level and over the
*Adapted from Suneja et al. (2019) Training Manual on Herbarium Methods. ICAR-NBPGR, New Delhi
56 The Teaching Manual on Plant Taxonomy year’s different chemo cultivars varying in their aroma type have been selected by crossing with other cultivars or closely related species. Estimation of essential oil content and composition of basil varieties is very important and can serve as a useful classification of basil from different regions. Basil is known to have several chemotypes based on variation in essential oil composition. In O. basilicum var. basilicum showed four chemotypes: linalool rich, methyl chavicol rich, (E)-methyl cinnamate and mixed type having both linalool and methyl chavicol type. Among the O. basilicum varieties, linalool-rich chemotype was identified in group thyrsiflora, difforme, purpurascens and glabratum, whereas methyl chavicol- rich chemotype was found in pilosum. Essential oils of most of the Cymbopogon spp. are characterized by citral, geraniol, citronellol, citronellal, linalool, elemol, 1, 8-cineole, limonene, b-carophyllene, methyl heptenone, geranyl acetate and geranyl formate. The essential oil of palmarosa (C. martinii) has high content of geraniol (90%) rose like odour; lemongrass/ Cymbopogon citratus mainly citral, neral and geranial, C. parkeri and C. olivieri from Iran rich in piperitone, C. nardus from Malaysia for linalool; C. proximus from Cameroon in carene, C. schoenanthus (Tunisia) in limonene and C. pendulus from India in elemicin. However, chemotypes of C. citratus from Brazil, India, West and Eastern Africa and Asia showed neral and geranial rich oil. In Rosa rugosa flavonol glycosides serve as chemotaxonomic markers for the classification. Chemical composition of artemisia oils has been investigated in many species of Artemisia for chemotaxonomic reasons. Camphor, 1,8-cineole, camphene, terpinen-4-ol and a-terpineol are the main oil components of A. sieberi (Weyerstahl et al., 1993), A. hololeuca, A. gmelinii and A. pontica (Bodrug et al. 1987), whereas artemisia ketone made up 94% of the total oil of A. alba (Bodrug et al. 1987). Chemotaxonomic markers sulfur compounds in the species of the Old and New World Allium could delineate taxa across different sections as revealed by characteristic chromatographic patterns. Chemotaxonomy methods Different chemotaxonomic methods are based on identification of chemical constituents in chemo- types viz. glycosides, glucosinolates, alkaloids, polyphenols, carotenoids, phyto-sterols (stigmasterols, saponins etc.), essential oils (terpenoids), organic acids, sugars, oligosaccharides, amino acids, fatty acids, starch granule structure. Targeted compounds in the genera/species for chemo-taxonomic purpose enables easy distinction. However, in certain cases pattern of distribution or ratio of compounds also provides clear insights about chemotypes such as ratios of different fatty acids in Brassica species. The methods used for chemotaxonomic classification are better and advanced than classical ones. Modern analytical tools – super critical fluid extraction, pressurized liquid extraction, sonication/microwave assisted extraction enable rapid and complete extraction with little loss/degradation plant sample extraction or quantitative and qualitative estimation of metabolites. Similarly for estimation use of UPLC/HPLC/HPTLC/GC coupled with versatile and powerful detectors like triple quadrapole mass spectroscopic detectors enables identification and quantization of trace quantities of μg/ng/pg level, even in absence of standard reference compounds. They are rapid, non-destructive, highly cost-effective and easy to perform. Conclusion Applicability of these modern tools along with data from basic fields-morphology, anatomy will give best result in understanding of plant taxonomy.
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The Teaching Manual on Plant Taxonomy 8 Field Studies: Collection and Identification of Plants
Introduction
Field studies are undertaken by the organizations dealing with plant genetic resource (PGR) management, floristic surveys and biodiversity study. These activities collectively play a role in strengthening of plant genetic resources field experience. Methods through for planning and organizing a successful field study visits for collection of germplasm are similar to those of the floristic surveys and can be applied with minor modifications. The guidelines have been framed to help the users in following standard procedures in conducting the field visits.
Field visits in relevance to taxonomy may be benificial for study of: a) plant characters (canopy, bark, leaf fall, orientation, plant colour etc.) as visible in live material vs herbarium and, b) enhanced knowledge perception in allied field - ecology, diversity, population biology, etc. While moving in field, one of the basic requirements is to understand the floristic richness. Normally well known crops are easily recognized but some less-known species, crop wild relatives and wild economic plant species may demand extra efforts for identification.
Field visits
Preparatory steps before the trip
Pre-field visit activities such as delivering lectures and demonstrations on plant collecting, methods to collect and processing of germplasm and herbarium are a part of preparatory steps. Before hand the gaps for collection are identified through literature survey, study of previous collection mission, and published information. Major preparatory steps before the trip include: z Discussion on purpose of the field trip z Overview on the schedule z Collect literature and data on area of visit, and plant species likely to occur with emphasis on species of PGR value z View route map and photographs of the site to be visited z Assigning role of the “specialists” during the field trip
Planning of field visits may vary with respect to the objectives of the visits for herbarium preparation, the samples are collected at full bloom stage whereas for collecting germplasm, the seeds are collected at full physiological maturity. In a single trip, the collector may find difficulty in assembling the germplasm and herbarium both; two trips may be planned by the same team or else two different teams can visit with different objectives. For seed producing crops/species, exploration should be
59 Pandey et al. undertaken when crops/species are physiologically mature and ready for harvest. In case of species with shattering behaviour (crop wild relatives/wild species) material may not be easily collected and hence bagging of identified plants prior to shattering is advisable (or else the collecting from the ground may be possible). One should keep recording information and additional data using field record book. Annexure I privides essential equipment neede during field work. Plants must be carefully uprooted to ensure that the maximum genetic diversity is retained on-site and not destroyed, and much research is required to determine the best way of storing each species. Visit to herbaria and online databases available should be referred gathering data on distribution pattern, localities, diversity pattern and period of collection particularly for wild species.
Areas of visit: selection of areas of visit is based on the objectives of field visits. Germplasm and herbarium collection of an unrepresented taxa are exclusively made in areas which are rich in species diversity of targeted taxa. In educational/teaching programmes, the visit is planned to expose the students to learn about ecological influence and also inculcate the knowledge on existing diversity. Areas like public parks, biodiversity parks, public/educational parks have well labeled plants and data on the holdings are generally available with curators/ in-charges. The MCD Herbal Garden, Punjabi Bagh, Aravali Biodiversity Park and Yamuna Biodiversity Parks are some of the identified in Delhi and National Capital Region for educational trips by PGR faculty. Agricultural fields with crops may be targeted for collecting germplasm of rabi and kharif crop. Forest margins and open forest areas harbour the wild/ weedy plants with extent of diversity.
Field equipment/tools: while proceeding on field visits, one has to be well equipped with tools and material essential for conducting trips (refer to Annexure I). Regional/ national flora, digital herbaria, list of local names of plants, road-map, vegetation/climate map, list of rest-houses/ lodges, hotels, resting/ stay places and list of local contacts (phone, fax, e-mail) are essentials items required during field visits.
Field photography is an essential tool to facilitate capturing entire picture of the area along with plant diversity. Closer-view of plants/parts may be helpful in identification of characters which otherwise upon preparing a herbarium may be lost. Photographs/information of associated plants, soil type, canopy and standing crop are also important.
Establishing taxonomic identity
Germplasm material with unknown identity, or identity only with vernacular name should be collected along with herbarium specimen and photographs for identification/authentication. When a collector is unable to collect herbarium specimens, efforts should be made to retain fruits, flowers and leaves along with seeds, and also effort should be made to raise plants in grow-out to establish correct identity.
Most floras begin with a key to the plant families, which may be cumbersome process to use for identification because they take into account the variation within the flora. Thus, knowing the general characteristics of families helps in proceeding directly to the key of genera within that family. Practical steps taken for identification of plant taxa often depend on the experience of the identifier/determiner. Similarly, if known to have an idea as to the general group within a family to which the taxon belongs (e.g., a suspected genus), keys, illustrations, descriptions, within the group can be consulted.
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Type of material: normally 4-5 individual plants/parts having representation of all parts viz. flowers, or fruits or both should be collected for preparing herbarium specimen. Locality, date of collection and field notes should be clearly recorded. Characters which are lost on drying, or which may not be represented in the herbarium specimen (plant height), flower colour, leaflets (which may be shed on drying) should be mentioned in field notes. The detailed guidelines for preparation and processing of herbarium specimen are discussed in Chapter 9.
Depending on the objective's of the collection mission seed, vegetative propagule, in vitro material and pollen are collected. The herbarium specimens in general and especially of the wild types and wild relatives should be collected to help in identification/ authentication. Efforts should be made to collect economic products of local/specific use as supportive samples.
Identification: the process of identification necessitates describing the plant in question with complete morphological characterization. One should check the geographic range of the flora used. Cultivated plants can be particularly difficult to identify. This is true in part because the number of plants taken into cultivation is very high and may also be difficult to identify as they are continually being evolved from original native species and also through introduction from abroad.
Among the most popular methods for identifying plants the keys are probably the most popular, practical and utilized method of identification. Taxonomic keys are of two types: dichotomous and polyclave (also called multiple access or synoptic). Dichotomous keys are also called ‘forked keys’ are the most common type, consisting of a series of paired statements, termed couplets that describe some feature of the organism. The statements, or leads, are in direct contrast (i.e., mutually exclusive). To use the key, begin with the first couplet and select the statement that best fits your specimen. This will direct you to another couplet and ultimately provide the identity of your specimen. There are two types of dichotomous keys viz. indented keys and bracketed keys. They differ in the method by which the couplets are organized and how the user is directed to successive choices (Refer chapter 11 practical exercise). Polyclave key consists of a list of numerous character states, whereby the user selects all of states that match the specimen. Till date the polyclave keys are available for a limited taxonomic groups.
Written description: this is a good method of determining with certainty whether the range of variation of the unknown plant corresponds to that listed in the description of a known plant. An identifier has to compare features of the unknown plant with written descriptions of the possible known taxa. For descriptions use of a flora is narrowing down the possibilities of expected identity. In addition, the diagnostic characteristics from a long list of features may be difficult. Thus, written descriptions are best used to verify an identity after one or a few possibilities are worked out.
Specimen comparison: use of an identified herbarium specimen for comparing the plant in question is a quick and reliable method. Comparison to a herbarium specimen is practically limited to verifying an identity after a subset of possibilities is narrowed down. Collections, which house generally one specimen of each taxon for a given region (e.g., a state, district, county) are very useful. If a taxon can be narrowed to a smaller group, such as a family or genus, a quick search through a synoptic collection for that region may often allow identification of the unknown specimen. However, one should ensure the correct identity of available referable herbarium specimens.
61 Pandey et al.
Image comparison: an unknown plant may be identified by visually comparing it to photographs or illustrations of known taxa. These are usually obtained from books, although webpage images have now become a very useful resource. A practical problem with this method is that photographs and illustrations are usually available only for a small subset of possible taxa. However, visual comparison to an image can still be an excellent way to identify a plant (though full reliability is a major issue), particularly if the possibilities can be narrowed down beforehand. The major precaution about this method is that two or more taxa may look very similar and the differences between them may reside on obscure morphological features that are not easily visible in images. Thus, any match of the unknown to a visual image should be confirmed with a technical description of the plant.
Expert determination: method seeking help, preferably of an expert in the group in question requires sending a specimen for identification. If the expert is familiar with all recent literature on the group, his or her determination is often more accurate and current than any other source. Expert determination is often essential for certain groups in which species or infraspecific identification is very difficult.
After the entire process, one should not over rule the possibility that indicates that the unknown plant in question may be a new record or even new species (either native or naturalized) for the geographic range of that flora.
Conclusions
Success of field study lies if the purpose of visit accomplished. In this respect, material collected (germplasm and herbarium specimens) are well identified and deposited in repository. Each field study should generate a referable report indicating the purpose of visit, flora available and major concerns of PGR where thrust needs to be laid by organisations.
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Annexure I
List of items and equipment*
Survey / collecting items z Global Positioning System (GPS), digital camera with additional memory card, binocular, magnifying glasses, handheld microscope, digital vernier calliper and portable balance.
z Haversack/ kitbag, seed envelopes, cloth bags, polythene bags, aluminium and tag labels, drying sheets, old newspapers, plant press, moss, rubber bands, packing tape, sutli (thick and thin), secateur, scissors, knife, digger, torch light, measuring tape, passport data book, field note book, pencil, ballpoint pen and permanent marker.
z Others: stapler, candle, match box, water bottle, formaldehyde, hunter shoes, hand gloves, waist pouch, rain suit (shirts, trousers), rucksacks, sun glasses, etc.
Reference material z Regional/ national flora, digital herbarium, lap-top and accessories, list of local names of plants, road-map, vegetation/climate map, list of rest-houses/ lodges, hotels, resting/ stay places and list of local contacts (phone, fax, e- mail).
First aid box z Anti-malaria pills, anti-allergen tablets, pain killers, anti- amoebic and anti- diarrhoeal tablets, mosquito repellent, antifungal/ antibacterial/ antiseptic creams or lotions, cotton-packs, band-aid
z Dressing gauze, water-purifying tablets, etc.
(*adapted from Arora 1991 with modifications)
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Appendix I NATIONAL BUREAU OF PLANT GENETIC RESOUCES, NEW DELHI 110 012 PASSPORT DATA SHEET Date…………………Collector’s No. …………………………………..Accession No………………..… Botanical Name……………………………….Common Name (English)……………………………….. Crop/Vernacular Name………………..Cultivar Name………………Region Explored……………….… Village/Block………………………….District……………………State……………………………...... N E Latitude…………….. Longitude………………………. Altitude……………………………….m SW Temp………………….Rainfall………….. COLLECTION SITE: 1. Natural wild 2. Disturbed wild 3. Farmer’s field 4. Threshing yard 5. Fallow 6. Farm store 7. Market 8. Garden 9. Institute 10………………… BIOLOGICAL STATUS: 1. Wild 2. Weed 3. Landrace 4.Primitive cultivar 5. Breeder’s line FREQUENCY: 1. Abundant 2. Frequent 3. Occasional 4. Rare MATERIAL 1. Seeds 2. Fruits 3. Inflorescence 4. Roots 5. Tubers 6. Rhizomes 7. Suckers 8. Live plants 9. Herbarium 10…………………. BREEDING SYSTEM: 1. Self-pollinated 2. Cross-pollinated 3. Vegetatively propagated SAMPLE TYPE: 1. Population 2. Pure line 3. Individual plant SAMPLE METHOD: 1. Bulk 2. Random 3. Selective (non-random) HABITAT: 1. Cultivated 2. Disturbed 3. Partly disturbed 4. Rangeland 5……………… DISEASE SYMPTOMS: 1. Susceptible 2. Mildly susceptible 3. Tolerant 4. Resistant 5. Immune INSECT/PEST/NEMATODE 1. Mild 2. Moderate 3. High INFECTION: CULTURAL PRACTICES: 1. Irrigated 2. Rainfed 3. Arid 4. Wet 5……………………….. SEASON: 1. Kharif 2. Rabi 3. Spring-summer 4. Perennial type Approx. Sowing Date………; Approx. Harvesting Date…………….. ASSOCIATED CROP: 1. Sole 2.Mixed with………………………. SOIL COLOUR: 1. Black 2. Yellow 3. Red 4. Brown 5…………………… SOIL TEXURE: 1. Sandy 2. Sandy loam 3. Loam 4. Silt loam 5. Clay 6. Silt TOPOGRAPHY: 1. Swamp 2. Food plain 3. level 4. Undulating 5. Hilly dissected 6. Steeply dissected 7. Mountainous 8. Valley AGRONOMIC SCOPE: 1. Very poor 2. Poor 3. Average 4. Good 5. Very good ETHNOBOTANICAL USES PART(S): 1. Stem 2. Leaf 3. Root 4. Fruit 5. Flower 6. Whole plant 6. Seed 7. Others KIND: 1. Food 2. Medicine 3. Fiber 4. Timber 5. Fodder 6. Fuel 7. Insecticide/ Pesticide 8. Others HOW USED: INFORMANT(S): 1. Local Vaidya 2. Housewife 3. Old folk 4.Grazir/shepherd 5. Others PHOTOGRAPH: 1. Color 2. BW 3. Transparency FARMR’S DONOR’S NAME: ……………………………………ETHNIC GROUP: ……...... ………………………. ADDRESS: ....…………………………………………………………………...... ………………..
PLANT CHARACTERISTICS/USES ADDL.: ...... NOTES: ……………………………………………………………………………………………………...... ………………………………………………………………………………………………………………………..……...... ………………………………………………………………………………………………………………………..……......
64 The Teaching Manual on Plant Taxonomy 9 Field and Herbarium Methods
Introduction
Ideal herbarium specimens act as a useful tool in taxonomic studies. The herbarium specimens are prepared (using standard procedures) with unique characters (vegetative characters- roots, tubers, bulbs and rhizome, stipule, spine, spathe, bark, etc.; floral characters- flower/inflorescence and fruit characters). An ideal herbarium specimen should represent all plant parts and information on locality, habitat and other details about characters of plant in an area of collection. Where plant parts are difficult to process using standard methods, for examples the herbarium specimens of cultivated plants with bulky parts, these procedures may need certain additional steps. Field and herbarium methods for processing into specimens are based on same principles and can be applied depending upon the need.
There are two methods for processing of herbarium specimens: the “dry processing method” and “wet processing method”. The second method may be used when collector may not be able to process the specimen immediately or the material are difficult and proned to get damaged. The collected specimens are placed between sheets of paper and about 40-50 such specimens are tied together. These bundles of specimens are then placed in large polythene bags and formaldehyde solution is added. These bags are then sealed and stored till the collectors return to their base. The wet specimens are then carefully taken out and spread on fresh dry blotting sheets and dried (Saldanha and Nicolson 1976). If there is any probable delay in pressing of specimen immediately after collection it can be kept with water at base in a sealed container/ pot or in airtight packs (in Ziplock bag) containing 5-10% formaldehyde. Depending on size of plant or the bag/container in which specimen is to be collected, the specimen number can be accommodated.
The procedure for preparation of specimens in field and in herbarium may vary depending on type of material and purpose of collection. “Bulky herbarium” may be prepared as wet collection in 4 per cent formalin/ rectified spirit/formalin or special dried form/ cut section (ex. flower, fruit, bamboo culms, spathe, trunk of a tree) to represent characters difficult to preserve using standard drying procedures. “Bulky herbarium” may be pickled, air-dried, naturally dried plants/ parts (woody flowers, cones, fruits, capsules), vegetatively propagated and tuberous forms that need to be represented in herbarium for special purpose. In some herbaria, they may be part of carpological samples/ economic botany collections. Handling bulky herbarium is not only cumbersome, but difficult for study and space consuming.
Standard herbarium specimens have advantages over bulky herbarium as they: 1) are easy to handle, refer and study; 2) exchange is simple; 3) drying and mounting is convenient and economical; 4) require less space. But the disadvantageous due to: 1) characters lost on drying; 2) representation of part population or few plants; and 3) needs regular maintenance for pest free/dust free storage. In case of bulky herbarium, preservation method has advantages due to: 1) shape and other structural characters are retained for study; 2) represent nearest possible features for study. But disadvantages
65 Pandey et al. are: 1) bulky and difficult to handle for identification or study; 2) soft material and fragile material lose colour after long time; 3) routine maintenance such as refilling of storage medium; and 4) more space consuming.
Build-up of herbarium collections
Ideally specimen selected for making into herbarium should have both flowers and young fruits, taken during late flowering stage. Selection of materials depends on the essential or desirable additional parts to be collected for identification. Flow chart (Figure 1) depicts the steps followed from collection to inclusion of herbarium specimen. Source of material depends on activity with
Fig. 1. Flow chart of herbarium processing: collection to inclusion
66 The Teaching Manual on Plant Taxonomy which the herbarium is associated. Additions are made through collections from fields, material raised in experimental gardens and voucher samples and seed material deposited by researchers (Fig. 2). If herbarium is associated with collage, or research organization, contents may vary.
Fig. 2. Voucher samples prepared, ready for mounting
Plants are collected to represent population in field; sometimes biased sampling can be done of the selected type. Using a strong knife, a pair of pruning shears or secateurs, plant is dug out to take the underground parts. Polythene bag or vasculum (metal collecting vessels) is also used to collect the material. While collecting formaldehyde (about 1 per cent) may be spread to avoid any infection especially with bulky fruits, cucurbit material. Delicate plants that tend to wilt fast may be collected and pressed right in the field using thick blotters. A tag with collector number, date of collection, is attached to individual plants while collecting. Latitude-longitude, soil, temperature, rainfall data should be recorded in the site of collection. Ideally about 20-25 cm length of plant/ parts may favourably fit in a herbarium sheet. Normally a minimum of two specimens of the same collection has to be made; however for unique variant(s), 4-5 such specimens from same plant/locality are desirable (helpful for describing as new taxa in the future). A field record book containing information about the range of occurrence, plant features (tree canopy, leaf fall), soil and associated vegetation forms the base for
67 Pandey et al.
Fig. 3. Herbarium processing in field from collecting to drying: (top row) selecting the ideal material, putting price tags/labelling; (middle row) putting the collected material in polythene bag, pressing material between the blotters; (bottom row) pressing herbarium specimens in field press, using corrugated sheets in-between the blotters
Fig. 4. Mounting of herbarium specimens for inclusion in collection (top row) mounting specimen on board, disinfecting herbarium specimen using poisoning method; (middle row) deep-freezing under -200C temperature, storing in herbarium cabinets; (bottom row) scanning for virtual herbarium; data documentation
68 The Teaching Manual on Plant Taxonomy the preparation of herbarium label (altitude, latitude, longitude, slope/direction), soil and type of vegetation should be maintained.
Normally the minimum number of specimens in a collection should be three-five but if the plants are small an attempt is made to collect several (at least 5-6) specimens of the same plant from the same locality. The specimen should consist of whole plants complete with roots, stem, leaves, flowers and if possible fruits. Where the plants are shrubs or trees, it is necessary to select a portion as a representative specimen the size of which is normally determined by the size of the mounting sheet. In case of dioecious plants try to collect both male and female plants/ branches (to be given different number). When flowers and fruits are too large to be pressed with the leaves, they are processed separately or if can be dried (especially sponge gourd, smooth gourd, okra, many fruits) stored as bulky collection (in boxes). Extra specimens of the same collection can be made depending on the requirement; duplicate specimens when collected may be used for exchange/studies. In some taxa, fruits characters (peel in bitter gourds and its wild species, fiber in Luffa are very unique as , All additional notes as collector’s name and collection number, place and date of collection, and features of the plant not shown by the dried specimen as soil types, associated flora, distribution, etc. should be recorded in the field note book.
Individual specimen is neatly arranged with all plant parts well spread using blotters or newspaper sheets. Number of sheets may depend on type of material, for examples the cereals generally can be easily taken care while the vegetables especially the ones with fleshy material need many sheets to avoid fungal growth during initial processing phase. Similarly it also depends on the season when plants are dried. Generally during wet season much care with more sheets can be put for good results. Care should be taken to avoid overlapping of plant parts; corrugated sheets are placed between the blotters and the specimen if processing done using artificial drying method or during wet season. The whole bundle is tied using a strong belt/strap and placed in a plant press. Figure 3- 4 highlight the procedures involved in processing of herbarium vouchers.
Processing cultivated plants: cultivated plants have comparatively fleshy parts especially the fruit plants (cucurbits, solanaceous fruits), those with large leaves/ flower buds (cauliflower, cabbage) and many succulent leaves (spinach, portulaca, Malabar spinach) therefore difficult to press as herbarium specimen. There is choice to represent them in wet collection (4-10 per cent formalin) or in died form/ cut-section so as not to miss out characters during drying.
Drying methods
Pressing and drying are the two simultaneous processes in the processing of herbarium and majorly contribute to quality of herbarium specimen. When plucked from plant, the specimen should be arranged in such a way that all the characters are well represented. The ‘plant press’ containing the bundle of specimens (20-30 cm height) is left tied using a strong belt/strap is again put in the press for 24-36 hours. During this period (sweating period) maximum water loss is there from plant. When first opened, all plant parts are neatly rearranged on fresh blotters. Care must be taken to remove the damaged or pest-infected/infested portion, if any. Leaves shouldn’t be crowded or piled on top of each other. Bulky parts, e.g., bulbs, corms, tubers and fleshy rhizomes may be reduced by slicing off in such a manner not to affect the exposed surface. Some leaves should be turned upside down in
69 Pandey et al. order to make visible both the surfaces in the final specimen. If the parts are bulky, e.g., onion bulbs, expose a portion of them in the specimen.
The same process is repeated for about a week or until drying is complete (especially in succulent/ fleshy material). Plant specimens must be processed for drying right in the field (using field press) or at least on the same day (using heavy lab press). Used blotters may be recycled after drying (ensuring no infection). Extra blotters and corrugated sheets used between the specimens can enhance the drying process especially during humid or wet season. Plant specimens are usually processed right in the field or at least the same day. In case of any unintentional delay, wet preservation method may help. Pads of paper and cotton are helpful around the bulky portions of thick/ bulky specimens to avoid shrinkage. The excess moisture is lost (naturally or under artificial heat or microwave) (Fuller and Barber 1981). Gradual increase of pressure aids in gradual squeezing and water expression from parts and prevents curling and crushing of plant tissues. Sectioning flowers longitudinally and pressing them flat to exhibit the inner parts.
Box 1: Some Dos’ and Don’ts’ for NHCP users
Dos’
z Use only the visitors’ area designated for study in NHCP; observe silence while working z Do enter your name and address in visitors’ book before starting the work z Handle the specimen with utmost care as they are the most precious vouchers for genetic resource study z Immediately inform the curator on finding any discrepancy/ damage or misplacement of a specimen z Do put the ‘determinavet slip’, if sure of the wrong identity of herbarium specimen, if any z Handle the specimens after wearing mask and gloves especially while working with treated material; wash hands carefully after use z Close the storage chambers/ compactors immediately after use z Ensure to have emergency numbers/ contact numbers while working inside the herbarium; contact herbarium staff during emergency z Keep your valuables in safe custody while working
Don’ts
z Do not entre herbarium without permission of curator z Do not bring any raw material/wet material/ live plants/ other sources into the herbarium z Do not bring any eatables/ food material inside the herbarium z Do not bring any fire/ hazardous material inside the herbarium z Do not removed any specimen or part of the specimen during study; if broken keep it in pouch and inform curator z Do not stack herbarium folders one on the other or upside down z Do not take photographs without the permission from the authorities z Do not try to place back the specimens; it may tend to be in wrong place without consultation with herbarium staff
70 The Teaching Manual on Plant Taxonomy
Herbarium press for lab use is generally very heavy and may be madeup of metal; one can also prepare field press using card board/sun pack boards tied together by straps/ cord/bolts. During exploration trips, carrying hard wooden press is difficult. Instead of hardwood frames, lightwood frames may aid in better pressing of specimens.
New protocols on processing of cultivated plants need to be worked out. Material representation in physical form is essentially needed for PGR and teaching programmes. For this efforts are in progress for developing ecofriendly methods with low budgetary requirement and labour cost.
Alternative method, specimens after processing for 24 hours in field press are rearranged and placed over a heat source (drying chambers, ovens, stoves, etc.). The temperature is adjusted to 46-500C. The hot air passing through the corrugated sheets placed between the blotters dry the specimens. Time taken for drying varies with respect to type of material, season and habitat of collection and this procedure may be modified based. Technique are standardized using micro- wave for succulents or fleshy material such as fleshy roots in vegetables, big sized fruits as in cucurbits or large leaved plants like aroids roots/ tuberous material for effective drying (Pandey et al. 2006).
Fully dried specimens are grouped into bundles (containg 25-30 specimens/bundle) within thick sheets of cardboard, and tied tightly. Depending on weather they are to be retained for build-up or dispatched elsewhere they can be well labeled on outside sheet to designate them for further action. The packed bundle for dispatch may be clearly written with “Handle with Care” instruction as during transport extra care is needed for safe handling. Besides placing wet collection, bulky parts like fruits, succulent roots, stem etc. should be sectioned in longitudinal and transverse sections and dried separately and while mounting of specimen linked on same mounting sheet.
Preservation
The collected specimens are poisoned immediately after collection or at the time of mounting using chemical treatment (alcohol is particularly done to avoid the microbial damage under high humidity conditions in the field). Dipping/ spraying with saturated solution of mercuric chloride in ethyl alcohol and processing the same for drying is generally practiced. For mounted specimens, a brush may be used. Pouring 10% formalin over specimens contained in the press and placed in an airtight polythene bag.
Specimens housed in the cabinets over a period of time may need monitoring and fumigated when infestation of pests is high. Volatile poisonous liquids like carbon disulphide, methyl bromide, carbon tetrachloride are also used sometimes. Specimens should remain in airtight condition for 3- 4 days. These chemicals pose a health hazards and should be handled with great care.
A practice of deep freezing subjected to a period of 48-72 hours (at -200C) has been found effective in control of pests/pathogens during processing or under storage. This method is also used in new material received from outside. Repellants like naphthalene bolls kept in small muslin bags in between racks and regular dusting of powdered nephathelin is found to be effective to control mild infection by the storage pests. A roster of chart prepared for routine poisoning and dusting helps in managing/ monitoring damage (some families- Solanaceae, Cucurbitaceae, Apiaceae and Lamiaceae are more sensitive to infection than others and need routine treatment; grass family, zingibers, gymnosperms etc. are good storers).
71 Pandey et al.
Mounting of specimens
Completely dried, poisoned specimens are mounted on good quality heavy paper, standard-sized mounting sheets/boards of 29x41 cm. Different materials such as glue, paste, narrow strips of glued linen, a needle and thread, etc. are used for mounting (Fig. 5). The glue or paste is usually applied using a brush. An alternative procedure is to spread the glue over a sheet of glass over which the lower side of the plant is placed before mounting on sheet. Stiff/bulky plant parts are usually tied using needle and thread. The herbarium label (11x6.5cm) containing information on plant name, family, local name, date of collection, place of collection, collector number, status (flowering/vegetative) should be pasted on the bottom right hand corner with information typed or filled with permanent ink. A paper pouch for extra plant parts may be pasted on the bottom left hand corner. The herbarium sheet on which specimen is mounted records all information about the plant sampled. Herbarium label gives basic information on the specimen when collected from its natural habitat, the location, date of collection, collector’s name, identity etc. (Appendix 1-4). In the label, the latest accepted name should be filled.
The mounting board with pre-prepared label (typed/ handwritten) with botanical name written with correct author citation is pasted with glue and fixed on the lower right-hand corner before the specimens. For mounting, three different procedures are quite popular. Gluing/pasting is best for flat leaves and evenly placed. It is not easy to remove but difficult to mount. An efficient and effective way is to coat the surface of a glass or copper plate with glue (using paint brush), place the specimen on the plate and tap gently with forceps. The specimen (bottom side) is then lifted using forceps, inspected to check even distribution of glue and placed on the sheet. Leaves in many plants may be pasted/ glued to resemble their original position. Extra plant parts as segments of leaves, flower, bud, fruits and seeds should be placed in packets or envelopes and can be affixed to the herbarium sheet at this time. Herbarium pouch can be mounted later on the left side of board. Bulky herbarium can be placed in separate cabinets. Most specimens after gluing are strapped in some manner (with linen tape) and sewing with a heavy linen thread. Sewing is restricted to heavy stems, overlapping leaves, rhizomes, matted bases of grasses, large fruits, cones, heads, or other places where use of plastic or glue is impossible or impractical. Each knot on the back should be separate and not a continuous. Fig. 5. Herbarium specimen (mounted and processed)
72 The Teaching Manual on Plant Taxonomy
Herbarium disinfectants may be used by dipping or painting with an alcoholic solution (2%) of mercuric chloride. Specimens so treated should always be clearly labelled. Part of the material used for study if removed (microscopic study, sectional work) should be placed back in pouches for reuse. Any additional records like notes, observations can be drawn with pencil on the mounting sheet, or photograph etc. can be put in illustrative folder kept at the end of section.
Identification of the plant specimen and dispatch of material
Procedures for identification of taxa can be referred in chapter 7. Unidentified specimens when sent for identification or sent by post (ensure proper postage handing) to the institution/ specialist (packaging). Annotation or determinavit (det.) slip (small slip attached on the herbarium sheet) to indicate name changes/correct identity of a plant by person annotating should put on the herbarium sheet with his name and signature with date along with institutional affiliation. If herbarium is to be dispatched for study, donation, loan or for identification, the packaging has to be done appropriately. The box should be of the nearly of the same size of the specimen size to avoid any kind of rattling while movement or transit. If the size is a little more, put extra paper pads to avoid damage due to movement.
Indexing and documentation
After mounting, labeling and identification, specimens are given a Herbarium Accession Number to organize collection.
Types specimens are housed separately with special care and are not handled routinely. A system of different coloured genus folders for different geographic regions is used to facilitate quick review of general distribution of a species. Duplicate collections are properly numbered and placed separately and used in case of need for exchange or otherwise.
If as a result of changes in nomenclature, placement of specimen in herbarium is changed, a dummy folder can be put in the appropriate place noting for shift. Any additional collection associated with herbarium may be refer to additions of special collections, viz., wood samples, cones, capsules or any shattering plant material (which can be stored in boxes designed to fit on the shelves of herbarium cases). Photographs, drawings, maps etc. may be mounted on sheets or placed on envelopes. Illustrations, reprints and additional material may be kept at the end of species/ genus. Any unidentified materials may be kept at the last of each taxon section with label “Dubia” or “unidentified”. Incoming material should be indexed time to time and damaged specimen should be repaired / replaced. Details of herbarium label and record sheet duly filled with appropriate can be seen in Appendix I).
In recent years, to facilitate fast access (and avoid mishandling of dried specimens), digital scans/ images are being made available for use (www.kew.org/data/herb_digitisation.html; http:// www.efloras.org/object_page.aspx?object_id=60285&flora_id=2).
Storage
Classification based on family, alphabetic order, or uses as crop-groups such as cereals, millets, oilseeds, pulses, ornamentals, etc. and then alphabetic listing of genus and species (within the
73 Pandey et al. genus) may prove well to the agriculturists. If working on economically important plant groups, arrangement of specimens through alphabetic listing of families (genus, species, forma) as followed in NHCP, may be helpful. Collection from different localities/ regions can be demarcated in separate files with distinct colour codes (Pandey et al., 2015). Regardless of filing system used in herbarium, specimen should be arranged in an order that they will match to the label pasted adjacent to herbarium case. Type specimens should be kept in separate place from the main collections and should be treated with much care. For an established herbarium all the above activities are to be taken up in routine processes.
Herbarium methodology used in NHCP
Success of any system is based on quality of material handled and maintained. As a result of routine working, some essential guidelines (Pandey et al., 2019) are available which are strictly being followed. Herbarium specimens in the NHCP are processed in routine way as discussed above. In special case microwave drying methodology has been standardized and found suitable for crop taxa and fleshy material. This method is fast, efficient, economically viable and health friendly. Diverse forms of material received, processed and represented here needs case by case treatment (Allium technique). Some suggested methods for atypical material are discussed below:
Diversity in cultivars: Since the cultivated plants represent the spectrum of diversity, efforts should be made to represent the ideal specimens. Complementary material of cultivars, elite types, breeding lines should be represented in form of diversity charts, folders etc. and crossed referred to the representative material (with herbarium identity number). For example specimens of cultivars of cereals may be represented by few ideal specimens with variability in panicle//heads depicted in form of display material (mounted on herbarium boards). In maize, since the plants are tall, cobs are bulky, representative specimens with portions of tilt roots with underground roots and other aerial parts could be included; material representing shanks, silk color and kernel colour are to be displayed together, besides variability photographs to complement to main herbarium collection. Different cultivars of Abelmoschus esculentus are distinct in fruit morphology can best be represented as dried/ mature fruits.
Large specimens: pruning needs to be done to fold to the required size; give turn to form V or N shape. Specimens with big leaves/ parts like Musa, papaya, leafy brassicas, Araceae and Arecaceae are accommodated in standard herbarium sheet. Selected specimen may be split into two or three parts and pressed separately (put same number, e.g. NH232304a, b, c, d, etc.). Plants with large leaves can be represented by cutting the portion of leaf tip, base and striped from middle. Spathe of banana and ligule of bamboos, bark of trees are significant for identification and can be dried and put on full sheet with hand outline drawn on label.
Rhizomatous/tuberous/bulbous types: vegetatively propagated material/ bulky underground parts like potato, Dioscorea, Amorphophalus, taros etc. that lose their identity on drying may be depicted by photographs/outlines. Small sections of the peels, transverse section of succulent tuber/root can be dried and mounted with herbarium. In bulbous plants, Allium bulb with coat, portion of bulb cut open in longitudinal section, also the leaf if hollow/ flat can be noted as on drying this character is difficult to note. In rhizomatous taxa, Curcuma, Zingiber, Canna, Xanthosoma, leaf with petiole, rhizome cut in section and inflorescence (if available) can be represented. Root material like carrot,
74 The Teaching Manual on Plant Taxonomy radish, sugar beet, turnip etc can be represented as sections giving outline of the root shape and peel mount of the surface.
Aquatic plants: need to be collected along with water, transfer in muslin cloth and sheets (many fold) replace quickly to avoid any infection. Special drying with heavy blotters for Trapa, Euryale ferox, others can help quality processing. Artificial heat treatment for fast drying followed by repeated change (4-5 hrs) of heavy blotters (5-6 sheets in one plant) may yield best results. If the plants are very large specimens, can be cut into parts and dried in the same way but extra care has to be taken to avoid any fungal infection.
Fleshy material: mature fruit with longitudinal slit, horizontal slit opening the cavity to expose seeds are helpful in identification. A peel section with fruit surface showing texture of fruit wall, any ornamentation, etc. can be included in the mature-young stage and dried separately with same number and mounted with original material. Citrus fruits where the rind characters are very important for identification can be additionally be photographed or outline of fruit drawn on herbarium sheet. Cucurbit fruits have peel characters, fibres and shape to be unique and peel dried and pated with herbarium is desired, e.g. Luffa, Momordica, Cucumis (sativus/melo group).
Identification markers: Vigna species can be identified at the flowering or early fruiting with characters of ovary that can be represented with flower open. Gamopetalous flowers to be wide open by giving a slit mid way. photographs could be the best option. Delicate and small flowers like Cucumis, Luffa, Sesame can be pressed using tissue paper and handled carefully till they dry. In tree taxa, characters of wood/bark are unique and need to be sampled for identification.
Problem taxa: processing of certain taxa is difficult due to the problem of leaf or floral parts fall during drying. Citrus, many legumes, Moringa, etc. during drying can be treated using microwave heat in the beginning of processing to avoid formation of abscission layer and improve the quality of processed specimen (Fuller and Barber 1981). Using artificial sudden heat (electric iron press) at 600C or microwave drying followed by routine drying process can help. Specimens that tend to drop leaves due to abscission layer formation need boiling water treatment for one minute or more before pressing to kill the cells and prevent dropping of leaves. In NHCP, we have used heavy weight electric iron for this purpose. Treating specimens with formaldehyde before drying or preserving them in 5- 12% formaldehyde or various formalin-alcohol solutions with small amount of glycerine, extra blotters, applying salting ensure quick drying of difficult-to-dry specimens, such as succulents, basella, radish, etc. For extracting DNA for molecular or biochemical study to from herbarium material several method are adopted (Rogers and Bendich 1985; Drábková et al. 2002).
In NHCP a subset of herbarium material is also preserved for biosystematics study. Methodology of plant herbarium voucher preparation without involvement of chemicals and harsh environmental conditions is available with best results (Seshagirirao et al. 2016). Herbarium preparation using the “Plant Specimen Preparation Kit” (https://www.oshibana.com/herbarium/en/index.php) can be used for study of analysis of chemical, biochemical and molecular biology (Fig.6).
75 Pandey et al.
Fig. 6. Plant specimen preparation kit” (https://www.oshibana.com/herbarium/en/index.php)
Conclusions
New protocols on processing of cultivated plants need to be worked out. Material representation in physical form is essentially needed for PGR and teaching programmes. For this efforts are in progress for developing ecofriendly methods with low budgetary requirement and labour cost.
76 The Teaching Manual on Plant Taxonomy
Appendix I National Herbarium of Cultivated Plants (NHCP) NBPGR, New Delhi 110 012 Herbarium Record Botanical name :
Family :
Common / English name :
Local (place, town, dist., state) :
Date of collection :
Collector’s name and IC number :
Herbarium collected along with germplasm of wild relative : Yes / No
Field collection/grown in experimental conditions :
Identified by : Self /others
Number of specimens :
Additional material supplied :
Uses, if any, in locality of collection :
Notes : ......
......
......
......
Herbarium specimen number : ○○○○○○○○○○ ○○○○○○○○○○ ○○○○○○○○○○ ○○○○○○○○○○
12 3 4 5 ○○○○○○○○○ ○○○○○○○○○ ○○○○○○○○○ ○○○○○○○○○
77
The Teaching Manual on Plant Taxonomy 10 Taxonomic Literature: Role in Plant Systematics Study
Introduction
Plant taxonomic literature is one of the oldest and comprehensive literatures of science published/ documented. It appears in various forms such of flora, monographs, books, illustrations, indexes, and bibliographic references, guides, journals and other supportive documents which are the essential tool for taxonomy. Taxonomic literature is written in leading languages such as English, German, and Russian; though original descriptions are still written in Latin. Information about the newly described plants, their names and classification are quite often published in research journals, books and monographs. Taxonomy is fundamentally a descriptive and diagnostic science. Knowledge of taxonomic literature and related bibliographic aids are essential tools for scientific identification, nomenclature and classification of plants. This chapter illustrates on use of taxonomic literature in locating the relevant scientific information on a taxonomic group.
Types of taxonomic literature
Comprehensive taxonomic works in the form of floras, monographs, revisions, descriptions, illustrations and identification keys are useful for proper identification of unknown plants. Some of the historical works on literature in taxonomy are the works of Theophrastus, Pliny, Dioscorides, Albertus Magnus, Brunfels, Cesalpino, the Bauhins, Ray, Tournefort and Carolus Linnaeus, latter is regarded as the father of taxonomy. Some selected taxonomic literature is discussed below.
Indexes to plant names
Index of plant names is an alphabetical listing of taxa with reference to their publication. It provides references to the original publication of names and the placement of a particular plant in a classification
Table 1: Some information on important indices/lists Index Contents and other details Authority/linkage (abbreviated form) Index Kewensis (IK) Generic and binomial names of seed plants of the whole world Royal Botanic Gardens, given in an alphabetical order. Kew Gray Index (GI) All new names/new combinations of names of vascular plants Gray Herbarium, Harvard from the New World (America) University Australian Plant All Australian information on scientific plant names, author, Centre for Australian Names Index (APNI) original publication details (protologue), scientific literature, National Biodiversity typification details, distribution (in Australia); cultivars derived Research from the Australian flora Index Filicum Names of original publication of generic and species names of Williams and Norgate, ferns (included in the Index Kewensis) London Index Londinensis Vascular Plants (1753-1935) used in Index Londinensis (with Royal Botanic Gardens, the illustrations) Kew
79 Pandey et al. scheme and serve as an aid to quickly locate the source of original publication of a name, to learn if a particular name has been applied to a plant or to what order, family, subfamily or tribe, a plant of a given name may belong. Details on some indices are given below (table 1):
Other publications: Some other publications include, Biological Abstracts (a bi-weekly publication listing abstracts of papers appearing in scientific journals); Regnum Vegetabile (selective guide to older bibliographical details of botanical literature for type material, priority of names, dates of publication); Kew Records of Taxonomic Literature (Royal Botanic Gardens, Kew, listing all taxonomic literature published in periodicals, books and papers); Index to American Botanical Literature (Consortium for Educational Communication Bulletin Torrey Botanical Club listings arranged alphabetically by author under subject groups); Index to Author of Plant Names (the authors of plant scientific names of angiosperms, gymnosperms, pteridophytes, bryophytes, algae, fungi (IPN) and fossil plants); Index to Plant Chromosome Numbers (IPCN- original plant chromosome numbers of naturally occurring and cultivated plants); and Index Holmensis (lists plant distribution maps). Some selected one are discussed below.
Index Herbariorum (IH): IH is a directory of major herbaria of the world and associated staff. For any herbarium to make entry into the IH, it must have physical location, web address, contents (e.g., number and type of specimens), history, names, contact information and areas of expertise of associated staff. Only those collections that are permanent scientific repositories are included in IH. Each institution is assigned a permanent unique identifier number in the form of a single to four and eight letter code, a practice that dates from the founding of IH in 1935. For example, for the herbarium located in the ICAR-National Bureau of Plant Genetic resources, New Delhi called the National Herbarium of Crop Plants has the code ‘NHCP’. There are 3,001 active herbaria in the world, containing 387,007,790 specimens located in 176 countries. 12,174 staff members associated with these herbaria (Thiers 2017; sweetgum.nybg.org/science/ih/)
Floras, monographs and revisions
A flora is a systematic arrangement of the species of a given area or a particular region, usually restricted to a major segment of the plant kingdom (flowering plants, etc.), with keys and descriptions and often illustrations, by the use of which a user may determine the names and characteristics of the wild plants of an area. Based on the coverage, a flora may pertain to a country, a section of a country, a state, a valley, a desert, or a vicinity of a city.
A taxonomic monograph is a treatise including all significant information based on the analysis and synthesis of existing taxonomic knowledge of that taxon of the group (one family, tribe, or genus).
Taxonomic revision may be the preliminary work and differs from the monograph in its degree of scope and completeness. Often it accounts for only a section of a genus or any level taxon. In order to make revisions, comprehensive work from already attempted areas have to be studied.
Other supporting taxonomic literature
The above-mentioned taxonomic works of wider scope are more technical and take longer time to complete; there are other supporting sources of taxonomic literature, which are published within short duration of time. These publications are:
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Journals: the scientific journals (hard copy version and e-version) on systematic research published periodically are highly specialized and to update progress on new fields relating to the field of research, plants identification, new aspects studied. The research paper may focus on taxonomy or extended distribution of a taxon, new record of a species, nomenclatural changes, etc.
Field inventory: field inventory or also called the ‘botanical inventory’ is a list of the species occurring in an area. The composition of a field inventory may vary with growing season. Field inventories can be updated by repeatedly adding information. The inventories are developed for a specific goal, for example field inventories on: (i) floristic diversity, (ii) crop plant taxa, (iii) wild relatives of crops, (iv) weedy species of a region, etc. The most common types of field inventories in use are simple and advanced inventories.
Simple inventories (for routine use) may be prepared based on familiarity with the area as well as the plant species available. Person preparing simple inventory should be able to place an unidentified species in a larger taxonomic group (family or genus) and then use botanical keys and laboratory equipments to complete the identification. Less familiar species may either be new to the area or may occur in a different season; there are equal chances that they may have been overlooked during earlier studies. In contrast to the simple inventory, the advanced inventories provide comprehensive information on mapping of plant diversity, location data and additional details pertaining to the botanical study of an area. Field record books, data books, field guides, and modern equipments (polycorders for recording tree data, GIS- Global Information System, GPS-Global Positioning Systems) help in attaining more precision.
Fig. 1. Inventorization of crop plants: selecting material for study in farmer’s field (top); recording of information on plant use (bottom) (photo: Dr KC Bhatt, ICAR-NBPGR)
Catalogues: account for the taxonomy books in botanical titles, and are of special value in taxonomic studies. It is often necessary to settle information on full name of a particular author, the unabridged and exact title of a work, when it was published/edition issued.
Periodicals: periodicals appear at regular intervals (biweekly, monthly, or quarterly) and a volume usually comprises the issues of a calendar year. In evaluating their treatments an abstract is a brief factual summary of a paper, frequently prepared by its author, whereas a review is an often critical
81 Pandey et al. appraisal and evaluation of the paper, and is by a person other than the original author. Collectively these numbers or fascicles comprise a volume. Scientific periodicals usually are sponsored either by a scientific organization, such as a learned society, or an educational or non-profit research institution, viz. a university or museum.
Dictionaries and glossaries: a botanical dictionary may list and describe all known genera of certain plant groups e.g. A Dictionary of Flowering Plants and Ferns -JC Willis. A Portable Dictionary of Plants, their Classification and Users by Mabberley. A glossary is an alphabetical list of difficult terms with their interpretations. Modern manuals, and many floras include a glossary of the botanical terms employed. Several comprehensive and nearly all-inclusive glossaries in text have been published as separate works. Most botanical dictionaries are of plant names and are sources for the etymology of Latin or vernacular names, for biographical data of persons for whom plants have been named, and for vernacular names in various languages.
Legislation: since 1867 botanists have met somewhat regularly at the international level and agreed upon legislation in plant names. These rules and regulations are contained in the International Code of Botanical Nomenclature (ICBN now ICN). They are subject to revision at each Botanical Congress and a new edition is then prepared (Ref to chapter 4).
Illustrations/icons: these are compiled separately and serve as useful tool for identification. They are graphical details of the plant/parts with the text in the floras. Examples: Hooker’s Icones and Wight’s Icones. The non-botanical readers have no other means of acquiring knowledge than through the oral communication. This illustrates distinctive characters of the plants which acts as a ready reckoner of plant species of that area or region or part or state or country.
In addition to the above taxonomic literature, some significant sources given in Appendix I, II may be refered. Publications such as Prodromus Systematis Naturalis Regni Vegetabilis, Genera Plantarum, Genera Filicum, Die Naturlichen Pflanzenfamilien, Genera of Flowering Plants, Key to the Families of the Flowering Plants of the World and System et Phylogenia Magnoliophytorum are also available for similar use.
Conclusions
Taxonomic literatures are an important tools for plant systematics research. Centuries old reference data can be used to reconstruct the past climate history which can throw light on the modern day climate change. While different types of literatures (indices, floras, monographs, journals and keys) are most important sources of research, dictionaries, guides and illustrations serve as handy identification tools during the field survey and collection trips.
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Appendix I
Nomenclature/Taxonomy Databases
Grin Taxonomy www.ars-grin.gov/cgi-bin/npgs/html/index.pl) Includes accepted names, distribution, economic importance and bibliography for each plant. Searchable by scientific and common name.
International Code of Nomenclature for algae, fungi, and plants (http://www.iapt-taxon.org/nomen/main.php) An electronic version of the code adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011.
International Plant Names Index (www.ipni.org) A searchable database of names included in the Index Kewensis (IK), the Gray Card Index (GCI) and the Australian Plant Names Index (APNI). Includes names that have been published to date, but is not a source for verifying currently accepted names.
ITIS - Integrated Taxonomic Information System www.itis.gov Taxonomic database created through a partnership of U.S. federal and international agencies. Entries include authority, taxonomic rank, synonyms and common names, taxonomic serial number, and data source. Source for verifying current accepted names, but not complete like the Plant List.
The Plant List http://www.theplantlist.org The Plant List provides the Accepted Latin name for most plant species, with links to all Synonyms by which that species has been known.
Tropicos http://www.tropicos.org Missouri Botanical Garden’s VAST (VAScular Tropicos) nomenclature database and authority files. Searchable by scientific name. Source for current accepted names for selected vascular plants.
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Appendix II
Additional links, source of information/literature for identification and use of herbarium resources
Web links
z http://apps.kew.org/wcsp/prepareChecklist.do?checklist = selected_families%40%40204220720081409914 (for synonyms, distribution) z http://www.kew.org/data/grasses-syn.html (for grass synonymy) z http://www.iucnredlist.org/ (for threatened plants) z http://www.efloras.org/ (Pakistan, China, Nepal, North America) z http://www.ildis.org (for legumes) z http://envfor.nic.in/bsi/research.html (for threatened plants of India) z http://mobot.mobot.org/W3T/Search/ipcn.html (for chromosome numbers) z http://www.unep-wcmc.org/ (for threatened plants) z Flora of India (recent initiative) http://efloraindia.nic.in/efloraindia/homePage.action
Virtual Herbarium z JSTOR Global Plants z Kew herbarium catalogue (K) z Edinburgh herbarium catalogue (E) z Paris herbarium (P) z Chinese Virtual Herbarium (PE) z Harvard Herbarium (GH) z Linnean specimens typification project z IPK Gatersleben (GAT)- also botanical images
Indian Herbarium Online z JCB, Bengaluru z IIIM, Jammu z RPRC, Bhubaneswar z KFRI, Thrissur z NBRI, Lucknow z HIFT, Puducherry
Protologue/ Old literature z Biodiversity Heritage Library (its prototype was originally developed at the MOBOT as Botanicus) – 2005- ten major institutes have collaborated in bringing this to present form z Botanico-Periodicum-Huntianum (worldwide bibliography of periodicals published between 1665 and 1966 that included any botanical content and covered more than 12,000 titles published in more than 45 languages) z JSTOR by Ithaka Harbors, Inc.
Important Journals relating to Plant Taxonomy and Systematics z Bangladesh Journal of Botany z Blumea z Botanical Journal of The Linnean Society z Botanical Review z Botanical Studies (Botanical Bulletin of Academia Sinica) z Brittonia
84 The Teaching Manual on Plant Taxonomy z Genetic Resources and Crop Evolution z Journal of Threatened Taxa z Journal of the Torrey Botanical Society z Nordic Journal of Botany z Novon z Pakistan Journal of Botany z Silvae Genetica z Taxon z The Indian Forester z Annals of Missouri Botanical Garden z Rheedea z Bulletin of Botanical Survey of India (Nelumbo) z Phytomorphology z Journal of Economic and Taxonomic Botany z NEBios z Kew Bulletin z Garden’s Bulletin (Singapore)
Online Journal and their Links z American Journal of Botany (http://intl.amjbot.org) (http://www.amjbot.org/) z Annals of the Missouri Botanical Garden (http://www.botanicus.org/bibliography/b12973130) z Kew Bulletin (http://link.springer.com/journal/12225) z Plant Systematics and Evolution (http://link.springer.com/journal/606) z Systematic Botany (http://www.sysbot.org/)(http://www.bioone.org/loi/sbot); z Taxon (http://www.botanik.univie.ac.at/iapt/) z Rheedea (http://www.iaat.org.in/#) z PhytoKeys (http://phytokeys.pensoft.net/).
Databases z Solanaceae Source z Gymnosperm Database z Dipterocarpaceae Database z Gesneriaceae Database z Convolvulaceae Unlimited z BrassiBase z PALMweb z Grassbase-Kew z Index Herbariorum (http://sweetgum.nybg.org/science/ih/) z PGR Abstracts z ANGIOSPERM PHYLOGENY WEBSITE, version 13. z IAPT-APG
85
The Teaching Manual on Plant Taxonomy 11 Taxonomic Methods in Study of Angiosperm Families
Plant morphological (phytomorphological) tools based on visual identification of external plant parts/ structures of different species draw similarity or dissimilarity between the taxa to conclude the identity of a taxa. Application of plant morphology for taxonomic identification is convenient and is appreciated by field workers, surveyors and conservationists during field study, germplasm collection and conservation, biodiversity and plant systematics works. The aim of the practical exercise is to motivate students with enhanced perception, inculcate the habit to observe characters significant in identification and knowledge build-up on plant taxonomy. Study of minute details (ultra-structure) especially of floral and seed parts may be recorded through the microscopic observations (compound or scanning electron microscope). Out of over 140 plant families including Crop Wild Relatives of significant PGR value, only selected angiosperm families are dealt herein in detail through practical exercise. The students are asked to attempt: A) Exercise- Learning by Observing and; B) Exercise-Learning by Performing. For glossary of terms used in the text students should refer Lawrence 1951. Digital flower and floral formulae are denoted in illustration part of each family description. Practical Exercises A. Learning by observing The objective of this exercise is to learn taxonomy by way of repeated observations while visualising plants growing in the surroundings/an area. This is one of the most effective methods especially for the students/beginners of PGR science. For PGR taxonomy teaching programme, over 25 important families have been covered as a part of syllabus. Some of the selected families for the practical exercise are given below (Table 1). Some selected seeds studied for characters of shape, testa ornamentation and seed colour are given in table 2 below to facilitate identification. Characters of each selected family covering wide range of taxa are included here and may not always represent the small sample available with you.
Table 1: Salient features of selected angiosperm families with some examples Amaranthaceae (Amaranth family) Usually herbs, a few shrubs, leaves simple, opposite or alternate, often highly colored; flowers small, inconspicuous, showy in mass, actinomorphic; inflorescence a cymes; perianth 2-5, green or coloured, free or united; stamens 3-5 free, dithecous, antiphyllous (opposite the perianth segments), gynoecium bicarpellary or tricarpellary, unilocular with a single basal ovule; fruit one seeded nutletuticle. Examples: Achyranthes aspera, Alternanthera sessilis, Amaranthus viridis Photo: Amaranthus hypochondriacus inflorescence
87 Pandey et al.
Amaryllidaceae (Lily family) Perennial bulbous herbs; radical leaves and leafless scape, inflorescence monochasial cyme; two or many spathaceous bracts around the flowers; flowers hermaphrodite; perianth gamophyllous; stamens 6, epiphyllous; gynoecium tricarpellary, ovary trilocular inferior, axile placentation, fruit capsule (differs from family Liliaceae in having inferior ovary). Examples: Zephyranthes rosea, Cuban zephyrlily Photo: Zephyranthes rosea
Anacardiaceae (Mango family) Evergreen tree or shrubs, leaves alternate, simple or pinnately compound; inflorescence a panicle; flower pentamerous, acti- nomorphic, stamens 10, inserted at the base of an annular disc; carpels 1-2, ovary superior with one pendulous or ascending ovule; fruit a drupe. Examples: Mangifera indica/mango, Anacardium occidentale/ cashewnut Photo: Anacardium occidentale/cashew nut
Apocynaceae (Madar family) Herbs, shrubs and trees, with milky latex; leaves simple, flowers hermaphrodite, actinomorphic, hypogynous; calyx free or united; corolla gamopetalous, 5 lobed, campanulate, valvate; androecium epipetalous, gynoecium bicarpellary, syncarpous, ovary superior, fruit-follicle or berry; seeds with crown of hairs. Examples: Carissa carandus/karaunda; Vinca rosea/ sadabahar Photo: Vincao rosea/periwinkle flower
Apiaceae (Coriander family) Herbs with fistular stem, leaves much dissected mostly decompound, sheathing leaf base; inflorescence terminal umbelliform cymes; flowers epigynous, pentamerous, regular rarely zygomorphic, actinomorphic, pentamerous, stamens 5; gynoecium two carpeled, bicarpellary syncarpous, single, inferior ovary; fruit schizocarp two fused carpels separate to mericarps/ cremocarp (single seed) at maturity. Examples: Daucus carota subsp. sativus/ carrot; Coriandrum sativum/coriander Photo: Coriandrum sativum/coriander flower Foeniculum vulgare/fennel seed
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Araceae (Aroid family) Rhizomatous or tuberous large herbs with fleshly or woody stems, sometimes climbing through adventitious roots; leaf-forms variable, lamina incised or perforated, leaf-base sheathing; inflorescence densely flowered showy spadix, covered with a spathe or bract often coloured and subtented by spathe; spathe of bright colour; flowers di-or trimerous, unisexual (rarely bisexual), perianth absent or tepals 6, stamens forming synandrium, fruit berry. Examples: Colocasia esculenta/ arvi Photo: Tuberous stems of Colocasia esculanta/arvi
Arecaceae (Coconut family) Woody plants with stout unbranched stem terminating in crown of leaves; leaves large, compound, leathery, fan shaped/feather; inflorescence enclosed in a persistent spathe; flowers unisexual, perianth 6 (two whorls of 3 each), male flower 6 stamens (two whorls), anthers versatile; female flowers carpels three, ovary superior, trilocular or rarely unilocular; fruit berry or drupe; seed endospermic. Examples: Cocos nucifera/coconut; Areca catechu /arecanut Photo: Fruits of coconut
Dioscoreaceae (Yam family) Twining non-woody dioecious or monoecious vines with woody rhizomatous tuberous roots; leaves usually spiral, often cordate, or sagittate; inflorescences axillary panicles, racemes, spikes, flowers bracteates, bracteolate (one bracteole, rarely two), small regular, trimerous, perianth 6, in 2 whorls; androecium 6 or 3 (the inner whorl sometimes missing), stamens 6/3; isomerous with the perianth, or diplostemonous, anthers dorsifixed, or adnate; gynoecium syncarpous, tricapellary, pistil 3, inferior ovary trilocular, placentation axile, ovules 2 per locule, fruit fleshy, or non-fleshy; capsule or a berry or samara Examples: Dioscorea alata/ greater yam Photo: Vegetative greater yalm Euphorbiaceae (Indian gooseberry family) Annual perennial herbs, shrubs, or tree; sap often milky, stem fleshy, leaves simple; reduced to scales or spines; inflorescence racemose or cymose; cyathium, flower actinomorph; unisexual; hypogynous; perianth 5, free, sometimes totally absent; stamens: stamens 5; free; tricarpillary, syncarpous ovary superior; axile placentation; fruits shizocarpic Examples: Phyllanthus emblica/ aonla; Euphorbia tirucalli/ pencil tree Photo: Aonla fruit
Labiatae / Lamiaceae (Mint family) Annual herbs or rarely shrubs, stem herbaceous, quadrangular; glandular hairs present; leaves simple, opposite and decussate; inflorescence verticillaster (opposite axillary cymes), zygomorphic, bilabiate, hermaphrodite, hypogynous; sepals 4-5, fused, tubular of funnel shaped, petals 4-5, gamopetalous, stamens 4 didynamous; epipetalous, syncarpous, ovary superior; tetralocula due to formation of false septum; fruits carcerulus with persistant calyx, seeds with gelling quality on soaking in water. Examples: Ocimum tenuiflorum /sacred basil, basil; Salvia officinalis/garden sage. Photo: Verticillaster of holy basil
89 Pandey et al.
Moraceae (Mulberry-Fig family) Woody tree, herbs, shrubs or vines with gum/milky sap, leaves simple; inflorescence small, inconspicuous catkin or hypanthodium, flower actinomorphic, incomplete, unisexual, hypogynous; perianth 4 (in two whorls), stamens in male flowers 4-5, opposite to the perianth; female flowers with two carpels, ovary superior, apocarpous, placentation basal; fruits achene, drupe or nuts. Examples: Morus alba/ mulberry; Ficus benghalensis/ banyan. Photo: Ficus benghalensis/ripe fruit
Musaceae (Banana family) Very large perennial monoecious, or andromonoecious herbs (pseudo-stems constituted by succulent leaf bases), rhizomatous, leaves large, alternate, simple (becoming pseudo-pinnate by tearing between the lateral veins); flowers in boat shaped bracts, inflorescences terminal; unisexual flowers thyrses of few flowered cymes; flowers bracteates, zygomorphic, perianth 6 tepals, joined and free 2 whorled; corolla gamopetalous (5+1); bilabiate; androecium 5-6, free in 2 whorled; gynoecium tricapellary, 3 locular syncarpous; ovary inferior, 3 locular, placentation axile; fruit fleshy, indehiscent berry; seeds many. Examples: Musa acuminata/banana Photo: Banana plant
Myrtaceae (Jamun family) Tropical and subtropical evergreen trees/shrubs simple opposite leaves aromatic, gland dotted, entire margin; flower hermaphrodite, actinomorphic, epigynous; calyx 4-5, gamosepalous, sometimes thrown off as a lid; stamens indefinite, carpels 2-5 syncarpous, ovary inferior, placentation axile; fruit a berry or drupe. Examples: Syzygium cumini /jamun; Psidium guajava /guava Photo: Jamun fruits
Nymphaeaceae (Water-lily family) Aquatic herbs; large peltate/floating leaves; often showy flowers, perianth spiral, gradually passing from sepals to petals and petals to stamens; stamens many; carpels many in pits of torus; fruit a spongy berry or an etaerio of achene or nuts sunken in the pits of a torus. Related to lotus family/Nelumbonaceae) Examples: Euryale ferox / makhana Photo: Nymphaea / Water lily flower
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Papaveraceae (Poppy family) Herbs with coloured sap; flowers often showy, regular, 4 sepals four, free, petals short lived; stamens numerous, ovary superior, one-celled; fruit capsules having valves or pores. Examples: Papaver somniferum/opium poppy; Argemone mexicana/ Mexican poppy Photo: Papaver rhoeas/Reel poppy flower
Pedaliaceae (Sesame family) Herbs, mucilage containing glandular hairs; flowers zygomorphic, hoypogynous; calyx and corolla 5, fused, corolla bilabiate; stamens 4, epipetalous, sometimes 2; carpels 2, syncarpous, 4-loculed or incompletely 4-loculed, axile placentation; fruit capsule Examples: Sesamum indicum/ til; Pedalium murex/ bara gokhru Photo: Sesamum indicum / Til flower
Piperaceae (Papper family) Tropical herbs, shrubs, trees and vines; often ornamental, dioecious, synoecious; inflorescence a pendulous spike or catkin, fleshy axis; flower very reduced, without petals or sepals, stamen 1-10, distinct, ovary superior, 1 locule, 1 basal ovule, stigmas 2-5; fruit drupe or drupelet, fused with the bracts Examples: Piper nigrum/ black pepper; Piper betle/ betel leaf Photo: Piper nigrum / Herbarium specimen
Polygonaceae (Knotweed family) Herb, shrubs, and vines with jointed stems; leaves simple with sheaths encircling stems, nodes swollen; inflorescence racemose, flowers small, crowded, di-trimerous, hypogynous, hermaphrodite, polyphyllous in two whorls; stamens 6 (3 + 3) or more; carpels three united, unilocular, single basal ovule; fruit a nut, enclosed by persistent membranous perianth Examples: Fagopyrum esculentum/ kottu; Polygonum glabrum/ polygonum Photo: Fagopyrum esculentum flowers
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Zingiberaceae (Ginger gamily) Rhizomatous aromatic herbs; mostly with cane-like stem; juice often scented; zygomorphic usually showy marked differentiation of perianth into calyx and corolla, single stamen and large usually petaloid staminodium. Examples: Zingiber officinale/ ginger, Alpinia galangal/ galangal Photo: Kaempferia galangal flower
Table 2: Seed characters used for identification
Name of the species/ Seed photo, Name of the species/ Seed photo, Seed shape and size (mm) Seed shape and size (mm) colour/extension colour/extension Abutilon indicum (L.) Alternanthera pungens H. B. & K. Sweet Indian mallow Khaki weed (Malvaceae) (Amaranthaceae) Kidney shaped; with Ovate with marginal hilar concave face,colour notch at broad end; surface grey- purple smooth and shiny faint 2.55×2.44×1.53 reticulations, no visible 1.15×0.70×0.38 attached appendages Acalypha indica L. Indian copper leaf Amaranthus roxburghianus (Euphorbiaceae) H.W. Kung wild amaranth, pigweed (Amaranthaceae) Ovoid or obovate pointed apex; testa ornamentation Round to disc shaped or fine to deep longitudinal lenticular, small notch striations or rugose 1.07×1.23×0.97 apex; black- light brown; testa sculpturing or Achyranthes aspera L. Devils 1.03×0.93×0.41 appendage horsewhip (Amaranthaceae) Amaranthus spinosus L. Spiny pigweed Cylindrical and truncate (Amaranthaceae) above,surface smooth, shiny reticulations, apex Seed coat dark black, with non-persistent 3.87×1.31×1.22 obovate shaped, appendages surface shining. Ageratum conyzoides L. 0.92×0.90×0.46 Goat weed Amaranthus viridis Hook. F. (Asteraceae) Slender amaranth (Amaranthaceae) Achene, black colored, oblong hexagonal, Oval-roundish tapering white hairs on coloured towards the hilum; hilum testa; pappus, cream 3.45×0.95×0.85 small notched; surface coloured shining and no visible 1.01×0.94×0.43 appendages
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Name of the species/ Seed photo, Name of the species/ Seed photo, Seed shape and size (mm) Seed shape and size (mm) colour/extension colour/extension Anagallis arvensis L. Apluda mutica L. Scarlet pimpernel Mauritian grass (Primulaceae) (Poaceae) Globose- angular- Spikelet compressed pyramidal, surface (both dorsally and pitted, reddish- ventrally), glumes two brown scales, 1.03×0.93×0.41 and equal; lower 1.78×1.55×1.52 hilar scar narrow glume leathery, upper glume thin; awnless; Anethum sowa Kurz. caryopsis compressed Indian dill dorsiventrally, ovate, no (Apiaceae) special appendages Seed mericarp ellipsoid- Argemone mexicana L. oblong, dorsal and Mexican prickly poppy, intermediate ribs Satyanashi forms prominent 0.92×0.90×0.46 (Papavaraceae) striations, wings thin Surface black, globular, Antigonon leptopus Hook & Arn. pointed ;elongated hilum, Coral vine, Thai vine testa shiny, heavily (Polygonaceae) 2.80×1.41×1.33 reticulated giving pitted Smooth and shiny; angular appearance shaped, surface glossy; attached appendages formed by persistent 1.01×0.94×0.43 perianth, pointed beak
Students are asked to go around the institute campus and click pictures of plants belonging to different families. Note down the diagnostic features of each species observed by them, prepare a table as given above with photos of plant/part. Repeat this exercise till you learn the features and collect flowering specimen of plant with pictures of each quickly appearing in your mind.
For seed identification exercise, students should visit the Conservation Laboratory and try to record the seed characters of diverse germplasm being processed. Based on some identifiable features try to link seed characters to families discussed above.
B. Learning by performing
Collection: collect five plant species with flowers and fruits. Examine each character visually and list the one that make it different from other species. You may use hand lens for study of minute parts; for ultra-microscopic characters use a dissecting microscope.
Description: plant description is assigning features or attributes to an entity. An important concept in taxonomic description is to identify a character (a feature) and character states (two or more forms of a character). Obtain a shoot (stem + leaves) from each of several species. Discuss what is characters and corresponding character states, using table 3 below. The objective of this exercise is to discriminate characters and character states for each provided plant/plant family. Describe the
93 Pandey et al. vegetative and reproductive parts using appropriate terminology. Discuss why you have used the particular ‘term’ for describing each character or character state in descriptive morphology.
Examples z Habit: erect, prostrate z Root: simple, fibrous z Leaf: simple, compound; petiolate, sessile z Stem: green, yellow; smooth, spineless z Inflorescence: raceme, cyme, panicle z Flower: actinomorphic, zygomorphic; red, pink, white z Calyx: free or united, narrow, lanceolate, tip acute, mucronate z Corolla: white, pink, gamopetalous or polypetalous z Androecium: 4, 5; free, united; green/yellow, violet coloured filaments z Gynoecium: ovary inferior, superior; tricarpellary, bicarpellary; syncarpous; stigma tip flat, pointed z Fruit: berry, drupe; green, red on ripening z Seed: grey, black; size-2-5mm; surface smooth, rugose; hilum depressed, flat
Table 3: Recording of descriptive character(s) for five selected species S. no. Characters Species A Species B Species C Species D Species E 1 Habit 2 Root 3 Stem 4 Leaf 5 Inflorescence 6 Flower 7 Calyx 8 Corolla 9 Androecium 10 Gynoecium 11 Fruit 12 Seed
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Scoring of identification characters z A character is a measurable unit of a taxonomic trait (qualitative and quantitative). z Characters are chosen because they are informative and fixed for a taxon. z A character state is a value that the character is assigned to. z Based on the values, a character may give binary, discrete, continuous score; score each character/character state in grade of 0-9 or 1-10. z Construct a phylogeny tree based on the scoring of characters.
Methods for identification of a plant are discussed in chapter 8. In this chapter, we mainly focus on identification key as a tool. Working in a group, construct an indented and numbered dichotomous taxonomic key to the species that you studied above. Start grouping the given specimens into two groups based on the most distinguishing character (similarity or dissimilarity) that separates the two groups (each group having a different character/state of the character). This character and its character states are the first couplet (composed of two leads) of the key. Divide each of these groups into two subgroups. Continue this until left with one species/sample. In writing the key, be sure to list the organ or part first, then the character state. Prefer to use only those characteristics visible with the naked eye.
Table 4: Scoring of character Species Character no. 1 Character no. 2 Character no. 3 Character no. 4 Character no. 5 A B C D E
Nomenclature
Each and every taxon/species has a valid name (botanical name) and has to be pronounced in a certain way. We can practice correct pronunciation by repeating and understanding the nomenclature. Use references to record the etymology (derivation and meaning) of these scientific names. Working for memorizing the scientific names of the plant species facilitates fast understanding.
Observe five common species growing in your campus, record their names using methods discussed in chapter 4. Try to know plants by local/common names and link them to botanical names. Use one or more of three methods to remember names: learn the etymology of the genus and specific epithet names and mentally connect that meaning with the plant; use a an image, to associate the plant with a word that sounds like the scientific name of the species; and repeat until the name becomes familiar. Recite each of the name with a digital picture of the plant shown to you. For current nomenclature refer to chapter 4.
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Classification
Go around in your campus with tools required for collection of specimens for identification (Chapter 9). List plant species with the most diagnostic features (1-2 only). Try to identify family name based on these characters, and also data on uses (if known). The common name, family and native distribution of each of these species, may be recorded data in the table given below:
Species Diagnostic character(s) Family Wild/ cultivated; use A B C D E
Preparing key to selected plants in Old Campus, ICAR-NBPGR, New Delhi
1. Evergreen tree 2. Tall tree, stem no thorns, inflorescence with small many flowers 3. Leaves glossy in whorls of three to ten, inflorescence compound umbels Flowers off-white, very fragrant, fruit long hanging pods - Alstonia scholaris
3. Leaves simple, leathery, alternate, inflorescence hypenthodium or panicle 4. Leaf broad, villous, oval, glossy, branches with aerial roots, white milky fluid oozes on breaking, inflorescence a hypanthodium orange on ripening - Ficus benghalensis
4. Leaves, oblong-lanceolate, glossy dark green above margin unduting, inflorescence terminal panicles, flower off-white, small, fruit drupe - Mangifera indica
2. Short trees or shrubs (2.5-4.5 m), sometimes stem bearing small thorns Leaves gland dotted, dark glossy green, flowers white, borne singly or 2-5 fin number in leaf-axils, aromatic with citrus type odour - Citrus japonica
1. Deciduous tree Leaves pinnately compound, pods oblong, flat, thin, strap-like light brown - Dalbergia sissoo
Preparation of plant check-list a) For any floristic survey(s) to be undertaken, check-lists are the starting points. Plants are recorded as per their location in field and season of appearance/occurrence. Vouchers of herbarium specimens are prepared as per the standard procedures and deposited in a herbarium after
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due identification (if not known, provide all supporting data as per herbarium label information; refer chapter 10). b) Students are asked to make a check-list of plant species in your campus, and classify them in the table given below:
Species Family Distribution and nativity Economic uses Diagnostic character(s)
A B C D JE c) Record latitude and longitude data of the area of plant occurrence using GPS method. Cast the location data on layout map using standard method for DIVA-GIS application.
C. Taxonomic descriptions of Selected Plant Families
This exercise has been planned to help the students to practice ‘Plant Description’ of a given taxon. Correct usage of taxonomic terminology for describing a taxon leads to nearest and correct identity of a plant species. Before conducting this exercise, the students are advised to go through chapter 2. Part ‘C’ includes ten selected families, prioritized on the basis of their agricultural importance. Selected photographs and economic parts and digital flower and floral formula (disgramatic and numerical depiction of floral parts) are included. While studying a family, students should take support from the taxon sheet provided here. It may not always represent the observations made by you in a material provided for study.
97 Pandey et al. Family Alliaceae (Onion family)
Habit: perennial, bulbous scapigerous herbs, sometimes rhizomatous Roots: fibrous, sometimes swollen or fleshy Stem: condensed, discoid Leaves: radical, fistular (cylindrical-semi-cylindrical), angular, filiform, flat or lanceolate, leaf bases sheathing, grow from bulb base, alternately or spirally arranged Inflorescence: cymose umbel enclosed in a spathe when young Flower:many, pedicillate, actinomorphic, hermaphrodite, hypogynous, sometimes replaced by small bulblets Tepals: six (in two whorls), free or connate, variously colured Androecium: stamens six, free or connate Gynoecium: ovary trilocular, superior, one style, placentation axile Fruits: dry capsule, dehiscent, loculicidal Seed: compressed to sub-globose, black, sometimes winged, surface shining or rough Significant characters: onion-like or garlic-like odour on crushing Related family: Liliaceae Note: also put under family Amaryllidaceae (GRIN) but differs in ovaries position Examples: Onion, garlic, chives, shallot
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Fig. a. Alliaceae: Flowers of Allium schoenoprasum; A. chinese and A. tuberosum; diagramatic illustration of major parts of Allium; digital flower and formula
99 Pandey et al. Family Asteraceae (Aster family)
Habit: herbs, shrubs, rarely trees
Root: tap root, sometimes modified into tubers
Stem: erect or prostrate, herbaceous or woody (Artemisia), cylindrical, glabrous, solid or fistular, hairy, sometimes with latex, stem tubers
Leaf: alternate rarely opposite or whorled; leaves may be radical, petiolate or sessile, exstipulate, mostly simple sometimes scale-like, unicostate or multicostate reticulate venation.
Inflorescence: capitulum (head) with two types of florets- ray-florets and disc florets; ray-florets (female or neuter), disc florets (hermaphrodite or male); rarely complete head with unisexual florets; bracteate, sessile, pentamerous, epigynous and inconspicious
Ray-florets: zygomorphic, ligulate, pistillate, or neuter or sometimes bisexual, epigynous
Calyx: modified into pappus, absent or scale-like
Corolla: petals five, gamopetalous, variable in colour, ligulate, strap-shaped, valvate
Androecium: absent
Gynoecium: absent or bicarpellary, syncarpous, inferior, unilocular with basal placentation, style one, stigma bifid
Fruit: cypsela
Seed: non-endospermic
Disc-florets: sessile, hermaphrodite, actinomorphic, pentamerous, epigynous and tubular
Calyx: modified into pappus or scale, persistent
Corolla: petals five, gamopetalous, tubular, coloured
Androecium: stamens five, epipetalous, syngenesious dithecous, introrse, dehiscing longitudinally
Gynoecium: bicarpellary, syncarpous, ovary inferior, unilocular, basal placentation, style simple, stigma bifid
Fruit: cypsela
Seed: non-endospermic
Notes: family divided into two sub-families: a. sub-family Asteroideae (flowers disc not ligulate, latex rare); and b. sub-family Lactucoideae (flowers ligulate latex present)
Example: Helianthus annuus/Sunflower
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Vernonia pappus, ray floret and disc florets
Fig. b. Asteraceae: Field view of sunflower; flower with ray and disc florets; ray florets of Vernonia amygdatina; seeds of V. amygdalina; digital flower and formula
101 Pandey et al. Family Brassicaceae (Mustard family)
Habit: herbs, annual or biennial or shrubs; sometimes reproduce through bulbils
Roots: tap root, swollen conical, fusiform or napiform, coral roots
Stem: herbaceous, erect, rarely woody, glabrous or hairy
Leaves: alternate or opposite, simple, cauline or radical, generally sessile, hairy, entire and with unicostate reticulate venation
Inflorescence: raceme, corymbose
Flower: tetramerous, hermaphrodite, actinomorphic (rarely zygomorphic), hypogynous, complete or incomplete, nectarines discoid, variable in number, present at base of stamens
Calyx: sepals 4 (arranged in two whorls of two each), polysepalous (2 antero-posterior and 2 lateral), 2 lateral sepals may be saccate, imbricate aestivation, inferior
Corolla: petals 4, alternate with sepals, polypetalous, petals arranged in ‘cruciform’, equal
Androecium: stamens 6, arranged in two whorls, outer two stamens short and inner four long (2+4), tetradynamous, polyandrous, anthers dithecous basifixed, introrse; stamens variable in number
Gynoecium: bicarpellary (rarely tricarpellary), syncarpous, ovary superior, unilocular (becomes bilocular due to false septum called replum), parietal placentation, ovules many, style short, stigma simple or bifid
Fruit: siliqua, sometimes lomentum; splits on drying, seeds remain attached to the replum
Seed: ex-albuminous
Examples: Brassica oleracea var. botrytis/cauliflower; B. oleracea var. capitata/cabbage
Related families: Papaveraceae, Capparidaceae
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Fig. c. Brassicaceae: Field view of Brassica juncea; siliquae of B. juncea (photo-Dr Rashmi Yadav, ICAR- NBPGR); close-up of flower; seeds of mustard; digital flower and formula
103 Pandey et al. Family Cucurbitaceae (Gourd family)
Habit: annual or perennial herbs (rarely shrubs or small trees) trailing, prostrate
Root: thickened due to storage
Stem: climbing, angular, fistular
Leaves: alternate, petiole hollow, simple, lobed, palmately lobed, tendrils present in the axil or opposite to the leaf
Inflorescence: flowers solitary, racemose or cymose panicles
Flower:mostly unisexual/ rarely bisexual, incomplete, epigynous, mostly white or yellow, pentamerous, monoecious or less commonly dioecious
Male flower: produced in large numbers as compared to female flowers
Calyx: sepals 5, gamosepalous, sepals pointed, rarely petaloid, campanulate, aestivation imbricate
Corolla: petals 5, gamopetalous united at the base or polypetalous, campanulate, aestivation rotate, imbricate or valvate
Androecium: stamens five or less, sometimes free or combined to form a central column; anthers dithecous extrorse, sometimes syngenesious, dehiscence longitudinal or in curves
Genoecium: reduced, rudimentary or absent
Female flower: fewer in number than the male flowers
Calyx: sepals 5, gamosepalous, calyx tube adnate to the ovary wall; imbricate aestivation, superior
Corolla: petals 5, gamopetalous, inserted on calyx tube; imbricate aestivation, superior
Androecium: staminodes 0 or 3 or 5
Gynoecium: tricarpellary, syncarpous, ovary inferior, unilocular with parietal placentation, the intruding placentae make the ovary to appear trilocular (in cho-cho/ Sechium edule- ovary unilocular, single ovule)
Fruit: fleshy, indehiscent, berry or pepo, size variable
Seed: exalbuminous, flattened, numerous, cotyledons oily
Examples: Cucurbita pepo (pumpkin); Cucumis melo (melon)
Related family: Passifloraceae
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Fig. d. Cucurbitaceae: Twig of cucumber (Cucumis sativus) with female flowers; Fruits of Luffa acutangula; Fruits of Cucumis melo var. agrestis (kachri); Flower close-up of Luffa; digital flower and formula
105 Pandey et al. Family Fabaceae (Legume family)
Habit: annual or perennial, herbs, shrubs, vines, tree Roots: fibrous tap root, often with nodules in herbs for nitrogen fixing Stem: herbaceous or woody, cylindrical, tendril present Leaves: alternate, pinnately compound trifoliate, stipulate (often modified leaves, thrones, tendril) Inflorescence: racemose or cymose, flowers in clusters Flower: actinomorphic or zygomorphic; hermaphrodite, pentamerous, hypogynous (sometimes perigynous) Calyx: sepals 4-5, free or fused Corolla: petals 4-5, free or united, variously coloured Androecium: polyandrous, diadelphous, anther basifixed Carpel: monocarpellary, ovary superior, placentation marginal Fruits: legume, sometimes lomentum Seed: non-endospermic Related families: Rosaceae, Moringaceae Family Fabaceae divided into three subfamilies
Fig. e. Fabaceae: Field view; Close-up of cowpea flowers and pods; Flower of Clitoria ternatia; Variablity of cowpea seeds; digital flower and formula
106 The Teaching Manual on Plant Taxonomy
Subfamily (a) Papilionoideae (Pea family) Habit: trees, shrubs or herbs Stem: herbaceous, woody or climber, tendrils wiry, coiled and thread like Leaves: compound (rarely simple), alternate and stipulate, stipule often present, leafy; may be modified into tendrils Inflorescence: racemose or solitary axillary flower Flowers: bisexual, zygomorphic, perigynous, pentamerous Calyx: sepals 5, hairy Corolla:papilionaceous, standard or vexillum (upper posterior petal); wings (two lateral free petals); keel or carina (two anterior most petals) boat- shaped Androecium: stamens diadelphous (9+1: 9 fused to form a sheath around the pistil and one posterior free) Gynoecium: pistil simple, monocarpellary, unilocular, ovary superior, style bent at base, placentation marginal Fruit: legume or pod Examples: Pisum sativum/pea; Arachis hypogaea/ peanut
(b) Caesalpinoideae (Cassia family) Habit: tree or shrubs, some woody climbers Stem: erect, climbing Leaves: compound (rarely simple), pinnate Inflorescence: axillary or terminal raceme Flower: bisexual, zygomorphic Calyx: sepals 5, often coloured, free or connate Androecium: stamen 10 or less (rarely numerous) Gynoecium: carpel simple, ovary superior Fruit: legume Examples: Tamarindus indica/ imli; Bauhinia variegata/kachnar
(c) Mimosoideae (Acacia family) Habit: trees or shrubs; rarely climbers or herbs Caesalpinia bonduc Stem: erect, woody Leaves: pinnate, compound, alternate, stipules often modified into thorns Inflorescence: spike, head or umbel; rarely racemose Flowers: bisexual, actinomorphic, hypogynous to slightly perigynous Calyx: sepals 5, fused, toothed or lobed Corolla: petals 5, free or fused Androecium: stamens numerous, free, adnate to base of corolla (epipetalous) Gynoecium: simple, monocarpellary, unilocular, ovary superior, placentation marginal Fruit: legume, dehiscent or indehiscent Examples: Acacia nilotica/gum arabic tree; Mimosa pudica /chui mui Dichrostachys cinerea
107 Pandey et al. Family Malvaceae (Mallow family)
Habit: herbs, shrubs and trees;
Roots: tap root
Stem: herbaceous, woody, erect or spreading, young parts covered with stellate hairs, mucilaginous sap present
Leaves: alternate, simple, stipulate, stipules deciduous, entire or palmately lobed, margin wavy/ serrate, apex acute
Inflorescence: racemose or cymose raceme, panicle,
Flower: large showy, widely bell-shaped, solitary axillary/terminal, bracteolate in the form of epicalyx, hermaphrodite (rarely unisexual), actinomorphic, pentamerous, hypogynous
Epicalyx: 3, 7 to 9 or absent
Calyx: sepals 5, connate at the base, persistent, sometimes forming a tube, aestivation valvate
Corolla: petals 5, polypetalous (sometimes slightly connate at the base with the staminal tube-thus epipetalous), twisted, prominent veins on petals.
Androecium: stamens indefinite, monadelphous, forming a staminal tube; epipetalous staminal tube united with the corolla, anthers basifixed, filament short
Gynoecium: multicarpellary usually 3, 5, 10 or indefinite, syncarpous, ovary superior, penta- or multi-locular with axile placentation, ovules one to many in each locules; style one, passing through the staminal tube; stigma corresponds to the number of carpels
Fruit: schizocarpic, capsule, berry
Seed: non-endospermic, in some genera seed coat densely tomentose
Example: Gossypium arboreum/ oriental cotton; Abelmoschus esculentus/ okra
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Fig. f. Malvaceae: Flower of Abelmoschus tuberculatus, A. tetraphyllus; Fruits of A. tuberculatus; Capsules of Cotton; digital flower and formula
109 Pandey et al. Family Poaceae (wheat family)
Habit: herbs, annuals/perennials; shrubs or tree like
Root: fibrous, adventitious, fascicled or stilt
Stem: underground rhizome, herbaceous/woody, cylindrical culm with conspicuous nodes and internodes (fistular/hollow), glabrous or glaucous, commonly develops into tillers
Leaves:simple, alternate, exstipulate, sessile, ligulate, leaf base forming tubular sheath, sheath surrounding internode, ligule present at junction of the lamina
Inflorescence: compound spike (sessile or stalked); unit of inflorescence – spikelet (arranged on the main axis- rachilla); compound inflorescence- spike of spikelets (Triticum), panicle of spikelets (Avena); florets alternate or opposite on central axis, two glumes (sterile scales) on base of rachilla; glumes boat shaped and sterile, placed one above the other on opposite sides (lower one - first glume; upper - second glume), floret inferior palea or lemma and above it is superior palea, lemma awned (stiff hair)
Flower: bracteate and bracteolate, sessile, incomplete, hermaphrodite, or unisexual, zygomorphic, hypogynous
Perianth: lodicules (membranous scales) situated above and opposite to the superior palea/absent/ 2 or 3/ many
Androecium: stamens 3, rarely 6 or one; polyandrous, filaments long, anthers dithecous, versatile, linear, extrorse
Gynoecium: monocarpellary, ovary superior, unilocular single ovule, basal placentation, style short or absent, stigma two, branched, feathery or papillate
Fruit: caryopsis (achene with pericarp completely united or adherent with the seed coat), rarely nut or berry
Seed: endospermic, containing a single cotyledon (called scutellum) which is shield shaped and pressed against endosperm
Examples Oryza sativa / rice; Triticum aestivum / wheat
Related family: Cyperaceae
Family divided into sub-family Poideae (spikelets one to many flowered; rachilla continued above the floret); and sub-family Panicoideae (spikelets mostly two flowered, rarely one flowered, rachilla not continued above the upper floret)
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Fig. g. Poaceae: Wild rice in field; Landrace of rice in farmer's field (photo- Dr. DP Semwal, ICAR- NBPGR); digital flower and formula
111 Pandey et al. Family Rosaceae (Rose family)
Habit: herbs, shrubs or trees, annual or perennial Stem: erect, prostrate or climber, branched, hard and woody, runner or sucker; with spines or prickles Root: tap root, sometimes adventitious arising from stem cuttings Leaves: alternate rarely opposite, simple or compound, stipulate, stipule minute and caducous, adnate and persistent, leaf base conspicuous Inflorescence: solitary or grouped in racemose, terminal corymbose, terminal cyme or corymbose cyme Flower: actinomorphic (rarely zygomorphic), bisexual, pentamerous or tetramerous, hypogynous/ epigynous/perigynous; stipules represent epicalyx Calyx: sepals 5, gamosepalous, adnate to the receptacle; calyx tube free or adnate to ovary, green, imbricate or valvate aestivation Corolla: petals 4-5, or multiples of 5, polypetalous, rosaceous, inserted on the receptacle cup variously coloured; petals entirely absent, or petals may be indefinite; sometimes stamens may be transformed into petal like structures; imbricate aestivation in bud Androecium: stamens variable in number, free, borne on the rim of the torus, anthers small, dithecous, splitting longitudinally, introrse in bud Gynoecium: carpel 1or 5 or indefinite, apocarpous rarely syncarpous, ovary superior or sometimes inferior, axile placentation, nectar secreting disc present between stamens and carpels; syncarpous, placentation axile, if apocarpous then basal Fruit: variable from drupe, etario of achenes, berry and pome Seed: non-endospermic Examples: Fragaria vesca/strawberry; Rosa damascena/ Damask rose
Related families: Leguminosae and Saxifragaceae
Sub-families: Spiraeoideae, Pomoideae, Rosoideae, Neuradoideae, Prunoideae and Chrysobalanoideae differ widely in floral characters
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Fig. h. Rosaceae: Fruits of peaches; Flower of Prunus pashia; Rosa sinensis; hip of rose; Fruit of wild apple (Malus baccata); digital flower and formula
113 Pandey et al. Family Rutaceae (Orange family)
Habit: shrubs, trees, rarely erect herbs or climbers Root: tap root Stem: woody, erect, cylindrical, branched, solid often thorny, gland dotted Leaves: simple or compound; alternate or opposite, petiole winged, simple or compound-pinnate, palmate, margin entire or serrate, unicostate reticulate venation, gland dotted Inflorescence: cyme/ axillary/terminal corymb, racemose or solitary Flower: hermaphrodite or unisexual, hypogynous, actinomorphic (rarely zygomorphic), disc below the ovary Calyx: sepals 5 or 4, free or fused, in zygomorphic flower it becomes gamosepalous and tubular; imbricate; sometimes deciduous Corolla: petals 5 or 4, polypetalous rarely gamopetalous or absent, variously coloured, imbricate with strong fragrance Androecium: stamens obdiplostemonous, 10 - numerous (polyadelphous), dithecous, basifixed or versatile Gynoecium: carpels 5 or many, ovary superior, multilocular; pentacarpellary slightly united at the base or sides forming a deeply lobed ovary with fused styles originating from centre; carpel fully united only one celled with many parietal placentae; placentation axile; ovary superior with a prominent nectariferous disc below Fruit: capsule or berry, septicidal or loculicidal capsule, hesperidium, berry Seed: endospermic or exalbuminous Specific characters: aromatic odour Examples: Citrus maxima / chakotra; Aegle marmelos / bael
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Fig. i. Rutaceae: Tree of Aegle marmelos; Fruit of Citrus japonica; Fruit of C. indica; Section of hespiridium; digital flower and formula
115 Pandey et al. Family Solanaceae (Nightshade family)
Habit: mostly annual herbs to vines, shrubs and trees
Leaves: alternate, usually simple, entire or variously lobed to pinnate, no stipules
Inflorescenes: cymes or solitary flowers
Flowers: commonly wheel-shaped, bisexual/ perfect, actinomorphic or weakly zygomorphic, corolla plicate; stamens adnate to petal tube; bicarpellary, syncarpous, superior, 2-locular; many axile ovules
Calyx: gamosepalous, tubular-deeply cleft
Corolla: gamopetalous, shortly tubular-long, reflexed lobes to forms with a long tube and short lobes
Stamens: distinct, alternating with the corolla lobes, adnate to corolla tube or perigynous zone
Fruits: berry or septicidal capsules, rarely a drupe
Ovary: carpel 2-5, false septa (internal walls that subdivide each locule), compound pistil of 2 carpels, style single, ovary superior, axile placentation, nectary disk present around at base of ovary
Examples: Solanum melongena/ egg plant; Capsicum annuum/ pepper
Related families: Scrophulariaceae, Convolvulaceae
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Fig. j. Solanaceae: Plant of Solanum surattense; Flower of Datura; Solanum torvum; Fruits of S. nigrum; Herbarium of S. melongena var. insanum; digital flower and formula
117 Pandey et al.
References/ Selected Readings
Arora RK, Nayar ER (1984) Wild Relatives of Crop Plants in India. Sci. Monogr. 7, New Delhi.
Arora RK, Pandey A (1996) Wild Edible Plants of India: Diversity, Conservation and Use. National Bureau of Plant Genetic Resources, New Delhi.
Arora RK (1991) Plant diversity in the Indian gene centre In: Plant Genetic Resources: Conservation and Management (ed. Paroda, RS, Arora RK), International Board for Plant Genetic Resources, Regional Office, New Delhi, pp 25-54.
Camp WH and Gilly CL (1943) The structure and origin of species. Brittonia 4: 323-385. de Vries JN, Wietsma WA, Jongerius MC (1992) Introgression of characters from Allium roylei Stearn into A. cepa L. In: Hanelt P et al. (eds) The genus Allium- taxonomic problems and genetic resources IGCPR. Gatersleben, Germany, pp321-325
Drábková L, Kirschner J, Vlcek C (2002) Comparison of seven DNA extraction and amplification protocols in historical herbarium specimens of Juncaceae. Plant. Mol. Biol. Rep. 20:161-175.
Fuller TC, Barber GD (1981) A micro-wave oven method for drying succulent plant specimens. Taxon 30:867.
Graf AB (1982) Pictorial Cyclopedia of Exotic Plants from Tropical and Near-Tropic Regions. Exotica Series 4 International, Vol.1. Publ. Roehrs Company, USA.
Lawrence GHS (1951) Taxonomy of Flowering Plants. Oxford & IBH Publishing Co., Macmillan.
Linnaeus C (1753) Species Plantarum. In: Facsimile (ed 1957), London, Ray Society, British Museum.
Mayr E (1942) Systematic and the Origin of Species. Columbia University Press, New York.
Pandey A, Bhandari DC, Bhatt KC, Pareek SK, Tomar AK , Dhillon BS (2003) Wild Relatives of Crop Plants in India: Collection and Conservation. Agro-biodiversity (PGR)-41. National Agricultural Technology Project on Sustainable Management of Plant Biodiversity, National Bureau of Plant Genetic Resources, New Delhi.
Pandey A, Nayar ER, Gupta Rita (2006) An efficient methodology for processing of herbarium specimens of cultivated plants. Indian J Plant Genet Resour 19(1): 47-49.
Pandey A, Pradheep K, Gupta R (2015) Manual on National Herbarium of Cultivated Plants. National Bureau of Plant Genetic Resources, New Delhi.
Pandey Anjula (2019) Herbarium Management: Approach and Current Trends. ICAR-National Bureau of Plant Genetic Resources, New Delhi, India.
Pradheep K, Pandey A, Bhatt KC, Ahlawat SP, Semwal DP, Bansal KC (2015) Crop Wild Relatives: Identification, Collecting and Utilization. National Bureau of Plant Genetic Resources, New Delhi 110 012, pp 72-78.
118 The Teaching Manual on Plant Taxonomy
Porter CL (1959) Taxonomy of Flowering Plants. WH Freeman and Company, San Francisco, USA.
Rogers SO, Bendich AJ (1985) Extraction of DNA from Milligram Amounts of Fresh, Herbarium and Mummified Plant Tissues. Plant Mole Biol 5: 69-76.
Saldanha CJ, Nicolson DH (1976) Flora of Hasan District, Karnataka, India. Amerind Publishing Co. Pvt. Ltd. New Delhi.
Semwal DP, Ahlawat SP (2016) Applications of Geoinformatics in Plant Genetic Resources Studies ICAR- National Bureau of Plant Genetic Resources, Pusa Campus, New Delhi-110012 http:// www.nbpgr.ernet.in/NBPGRNew/Downloads/cid/Downloadfile.aspx?EntryId=7271
Seshagirirao K, Harikrishnanaik L, Venumadhav K, Nanibabu B, Jamir K, Ratnamma BK, Jena R, Babarao DK (2016) Preparation of herbarium specimen for plant identification and voucher number. Roxburghia 6(1-4):111-119.
Zeven AC, de Wet JMJ (1982) Dictionary of Cultivated Plants and their Regions of Diversity. Centre of Agricultural Publishing and Documentation, Wageningen, the Netherlands.
Tripathi Kuldeep, R Bhardwaj, S Bhalla,V Kaur, R Bansal, R Yadav, KK Gangopadhyay, A Kumar and R Chaudhury (2018) Plant Genetic Resources Evaluation: Principles and Procedures. Indian Council of Agricultural Research - National Bureau of Plant Genetic Resources (ICAR-NBPGR), New Delhi. Selected links https://quizlet.com/25556435/plant-taxonomy-terminology-flash-cards/
International Code of Nomenclature for algae, fungi, and plants - (http://www.iapt-taxon.org/nomen/main.php) http://vle.du.ac.in/mod/resource/view.php?id=13116) ISSN NO. 978-93-85611-90-2. Selected databases
Grin Taxonomy www.ars-grin.gov/cgi-bin/npgs/html/index.pl
International Code of Nomenclature for algae, fungi, and plants (http://www.iapt-taxon.org/nomen/main.php)
International Plant Names Index www.ipni.org
ITIS - Integrated Taxonomic Information System www.itis.gov
The Plant List http://www.theplantlist.org
Tropicos https://www.tropicos.org/
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