Unit II: Plant Morphology and Taxonomy of Angiosperm Chapter 3 Vegetative Morphology

Learning Objectives of shape, size and structure of plants and their parts (roots, stems, leaves, The learner will be able to, flowers, fruits and seeds). Study of • Explore the parts of the flowering morphology is important in taxonomy. plants Morphological features are important • Differentiate vegetative morphology in determining productivity of crops. and reproductive morphology Morphological characters indicate the specific habitats of living as well as the • Compare various root systems and fossil plants and help to correlate the their modifications distribution in space and time of fossil • Understand the stem modifications plants. Morphological features are also and functions significant for phylogeny. • Interpret the structure of leaf and functions of leaf Plant Morphology can be studied under two broad categories: A. Vegetative morphology – It Chapter Outline includes shoot system and root 3.1 Habit system 3.2 Plant habitat B. Reproductive morphology – It 3.3 Life Span includes Flower/inflorescence, Fruit and Seed 3.4 Parts of a flowering plant 3.5 Root System A. Vegetative morphology 3.6 Shoot system Vegetative morphology deals with the 3.7 Leaf study of shape, size and structure of plants and their parts roots, stems and The study of various external features of leaves. To understand the vegetative the organism is known as morphology. morphology the following important Plant morphology also known as components are to be studied. They are, external morphology deals with the study 1) Habit, 2) Habitat and 3) Lifespan.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 63 02-06-2018 13:48:22 3.1 Habit IV. Trees The general form of a plant is referred to as A tree is a stout, tall, perennial, woody habit. Based on habit plants are classified plant having one main stem called trunk into herbs, shrubs, climbers (vines) and with many lateral branches. Example: trees. mango, sapota, jack, fig, teak. If the trunk remains unbranched it is said to be I. Herbs caudex. Example: Palmyra, coconut. Herbs are soft stemmed plants with less wood or no wood. According to the 3.2 Plant habitat duration of their life they may be classified Depending upon where plants grow as annuals, biennials and perennials. habitats may be classified into major Perennial herbs having a bulb, corm, categories: I. Terrestrial and II.Aquatic. rhizome or tuber as the underground stem are termed as geophytes. Example: I. Terrestrial Phyllanthus amarus, Cleome viscosa. Plants growing on land are called II. Shrubs terrestrial plants. The following table illustrate the types of terrestrial plants A shrub is a perennial, woody plant classified based on their environmental with several main stems arising from the adaptation. ground level. Example: Hibiscus II. Aquatic III. Climbers (Vine) Plants that are living in water environment An elongated weak stem generally are called aquatic plants or hydrophytes. supported by means of climbing devices are called Climbers (vines) which may be 3.3 Life Span annual or perennial, herbaceous or woody. Based on life span plants are classified Liana is a vine that is perennial and woody. into 3 types. They are annual, biennial Liana’s are major components in the tree and perennial canopy layer of some tropical forests. Example: Ventilago, Entada, Bougainvillea.

Terrestrial habitat Types Nature of environmental adaptation Example Mesophytes Growing in soils with sufficient water Azadirachta indica Xerophytes Growing on dry habitats Opuntia, Euphorbia Psammophytes Growing on sand Ipomoea pes-caprae, Spinifex littoralis Lithophytes Growing on rock Many algae and lichens, Ficus spp

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 64 02-06-2018 13:48:22 Aquatic habitat Types Nature of environmental adaptation Example Free Floating Growing on water surface Eichhornia, Trapa, Pistia, Lemna Submerged Plants growing completely under water Hydrilla, Vallisneria Emergent Plants with roots or stems anchored to Limnophyton, Typha the substrate under water and aerial shoots growing above water Floating leaved Anchored at bottom but with floating Nelumbo, Nymphaea leaves Mangroves Plants growing emergent in marshy Avicennia, Rhizophora saline habitat

I. Annual (Therophyte or Ephemerals) consisting of an axis with an underground A plant that completes its life cycle in one “Root system” and an aerial “Shoot growing season. Example: Peas, maize, System”. The shoot system has a stem, water melon, groundnut, sunflower, rice branches and leaves. The root system and so on. consists of root and its lateral branches.

II. Biennial Flower Leaf Bud A plant that lives for two seasons, growing vegetatively during the first season and flowering and fruiting during the second season. Example: Onion, Lettuce, Fennel, Shoot Stem Carrot, Radish, Cabbage and Spinach. Root Primary root III. Perennial (Geophyte) Secondary root A plant that grows for many years that flowers and set fruits for several seasons during the life span. When they bear fruits every year, Figure: 3.1: Parts of a flowering plant they are called polycarpic. Example: mango, sapota. Some plants produce flowers and 3.5 Root System fruits only once and die after a vegetative growth of several years. These plants are The root is non-green, cylindrical called monocarpic. Example: Bamboo, descending axis of the plant that usually Agave, Musa, Talipot palm. grows into the soil (positively geotropic). It develops from the radicle which is the first structure that comes out when a seed 3.4 Parts of a flowering plant is placed in the soil. Root is responsible Flowering plants are called “Angiosperms” for absorption of water and nutrients and or Magnoliophytes. They are sporophytes anchoring the plant.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 65 02-06-2018 13:48:22 I. Characteristic features the root cap the following three distinct • Root is the descending portion of the zones have been classified based on their plant axis. meristematic activity. 1. Meristematic Zone • Generally non-green in colour as it lacks chlorophyll. 2. Zone of Elongation 3. Zone of Maturation • Does not possess nodes, internodes and buds (Exception in sweet potato and Root hair members of Rutaceae, roots bear buds which help in vegetative propagation) Region of Cell • It bears root hairs (To absorb water maturation and minerals from the soil) • It is positively geotropic and negatively phototropic in nature. Region of cell elongation II. Regions of root Root tip is covered by a dome shaped Region of cell division parenchymatous cells called root cap. Root cap It protects the meristematic cells in the Figure 3.2: Regions of root apex. In Pandanus multiple root cap is present. In Pistia instead of root cap root pocket is present. A few millimeters above

Table: Root zones 1. Meristematic Zone 2. Zone of Feature 3. Zone of Maturation Region of cell division Elongation Position It lies just above the It lies just above the It lies above the zone root cap meristematic zone of elongation.

Types of Meristematic cells, Elongated cells Mature differentiated cells actively divide and cells continuously increase in number Functions This is the main The cells increase The cells differentiate growing tip of the the length and cause into various tissues like root enlargement of the epidermis, cortex and root. vascular bundles. It also produces root hairs which absorb water and minerals from the soil

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 66 02-06-2018 13:48:23 3.5.1 Types of root root. It may develop from the base of the stem or nodes or internodes. Example: Fibrous root Tap root system Monstera deliciosa, Ficus benghalensis, system Piper nigrum. In most of the monocots the primary root of the seedling is short lived and lateral roots arise from various regions of the plant body. These are bunch of thread-like roots equal in size which are collectively called fibrous root system generally found in grasses. Example: Oryza sativa, Eleusine coracana, Pennisetum americanum.

III. Functions of root Figure 3.3: Types of root system Root performs two kinds of functions I. Tap root system namely primary and secondary functions. Primary root is the direct prolongation Primary function of the radicle. When the primary root persists and continues to grow as in 1. Absorb water and minerals from soil. dicotyledons, it forms the main root of 2. Help to anchor the plant firmly in the plant and is called the tap root. Tap the soil. root produces lateral roots that further Secondary function branches into finer roots. Lateral roots In some plants roots perform additional along with its branches together called as functions. These are called secondary secondary roots. functions. To perform additional II. Adventitious root system functions, these roots are modified in Root developing from any part of the plant their structure. other than radicle is called adventitious

Root modification

Tap root modification Adventitious root modification

Storage Breathing root Storage Mechanical support Vital function

i. Conical i.Tuberous root i. Prop root i. Epiphytic root ii. Fusiform ii. Fasciculated root ii. Stilt root ii. Foliar root iii. Napiform iii. Nodulose root iii. Climbing root iii. Sucking root iv. Moniliform root iv. Buttress root iv. Photosynthetic v. Annulated root root

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 67 02-06-2018 13:48:23 3.5.2 Modifications of root b. Breathing root I. Tap root modification Some mangrove plants like Avicennia, Rhizophora, Bruguiera develop special kinds a. Storage roots of roots (Negatively geotropic) for respiration 1. Conical Root because the soil becomes saturated with These are cone like, broad at the base water and aeration is very poor. They and gradually tapering towards the apex. have a large number of breathing pores or Example: Daucus carota. pneumatophores for exchange of gases.

2. Fusiform root II. Adventitious root modification These roots are swollen in the middle and a. Storage roots tapering towards both ends. Example: 1. Tuberous root Raphanus sativus These roots are swollen without any 3. Napiform root definite shape. Tuberous roots are It is very broad and suddenly tapers like a produced singly and not in clusters. tail at the apex. Example: Beta vulgaris Example: Ipomoea batatas. 2. Fasciculated root These roots are in cluster from the base of the stem Example: Dahlia, Asparagus, Ruellia. 3. Nodulose root In this type of roots swelling occurs only near the tips. Example: Maranta (arrow root) Curcuma amada (mango ginger), Curcuma longa (turmeric) 4. Moniliform or Beaded root (a) (b) (c) These roots swell at frequent intervals giving them a beaded appearance. Example: Vitis, Portulaca, Momordica Indian spinach. 5. Annulated root (d) These roots have a series of ring- like swelling on their surface at regular intervals. Example: Ipecac (Psychotria) b. Mechanical support Figure 3.4: Tap root modification 1. Prop (Pillar) root (a) Daucus carota (b) Raphanus sativus These roots grow vertically downward (c) Beta vulgaris (d) Avicennia from the lateral branches into the soil. Pneumatophores

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 68 02-06-2018 13:48:24 Ipomoea batatas Dahlia Maranta Psychotria Figure 3.5: Adventitious Root Modification for Storage

Example: Ficus benghalensis (banyan tree), around the trunk. They grow obliquely Indian rubber. downwards and give support to huge trunks of trees. This is an adaptation 2. Stilt (Brace) root for tall rain forest trees. Example: silk These are thick roots growing obliquely cotton tree (Bombax), white cotton tree from the basal nodes of the main stem. (kapok), Terminalia arjuna, Delonix These provide mechanical support. regia, Pterygota alata. Example: Saccharum officinarum, Zeamays and Pandanus, Rhizophora. c. Vital functions 1. Epiphytic or velamen root 3. Climbing (clasping or clinging) roots Some epiphytic orchids develop a special These roots are produced from the nodes kind of aerial roots which hang freely in of the stem which attach themselves to the air. These roots develop a spongy tissue the support and help in climbing. To called velamen which helps in absorption ensure a foothold on the support they of moisture from the surrounding air. secrete a sticky juice which dries up in Example: Vanda, Dendrobium, Aerides. air, attaching the roots to the support. Example: Epipremnum pinnatum, Piper 2. Foliar root betel, Ficus pumila. Roots are produced from the veins or 4. Buttress root lamina of the leaf for the formation of new plant. Example: Bryophyllum, Begonia, In certain trees broad plank like Zamioculcas. outgrowths develop towards the base all

Ficus benghalensis Saccharum officinarum Epipremnum Bombax pinnatum Figure 3.6: Adventitious root modification for mechanical support

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 69 02-06-2018 13:48:27 3. Sucking or Haustorial roots I. Characteristic features of the stem These roots are found in parasitic plants. 1. The stem is usually the aerial portion Parasites develop adventitious roots from of the plant stem which penetrate into the tissue of the 2. It is positively phototropic and host plant and suck nutrients. negatively geotropic Example: Cuscuta (dodder), Cassytha, 3. It has nodes and internodes. Orobanche (broomrape), Viscum 4. Stem bears vegetative bud for vegetative (mistletoe), Dendrophthoe. growth of the plant, and floral buds for 4. Photosynthetic or assimilatory roots reproduction, and ends in a terminal Roots of some climbing or epiphytic bud. plants develop chlorophyll and turn green 5. The young stem is green and thus which help in photosynthesis. Example: carries out photosynthesis. Tinospora, Trapa natans (water chestnut), 6. During reproductive growth stem Taeniophyllum. bears flowers and fruits. 7. Branches arise exogenously 3.6 Shoot system 8. Some stems bears multicellular hairs The plumule of the embryo of a of different kinds. germinating seed grows into stem. The epicotyl elongates after embryo growth II. Functions of the stem into the axis (the stem) that bears leaves Primary functions from its tip, which contain the actively 1. Provides support and bears leaves, dividing cells of the shoot called apical flowers and fruits. meristem. Further cell divisions and 2. It transports water and mineral nutrients growth result in the formation of mass to the other parts from the root. of tissue called a leaf primordium. The point from which the leaf arises is called 3. It transports food prepared by leaves node. The region between two adjacent to other parts of the plant body. nodes is called internode.

clinging root Photosynthetic root hanging root

Vanda Bryophyllum Cuscuta Tinospora Figure 3.7: Adventitious Root Modification for Vital Functions

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 70 02-06-2018 13:48:30 Secondary functions 3. Extra axillary bud : These buds are 1. Food storage- Example: Solanum formed at nodes but outside the axil of tuberosum, Colocasia and Zingiber the leaf as in Solanum americanum. officinale 4. Accessory bud : An extra bud 2. Perennation / reproduction – Example: on either side (collateral bud) or Zingiber officinale, Curcuma longa above (superposed bud or serial bud) 3. Water storage – Example: Opuntia the axillary bud. Example: Citrus and 4. Bouyancy – Example: Neptunia Duranta 5. Photosynthesis – Example: Opuntia, 5. Adventitious buds: Buds arising at Ruscus, Casuarina, Euphorbia, any part other than stem are known Caralluma. as adventitious bud. Radical buds 6. Protection – Example: Citrus, Duranta, are those that arises from the lateral Bougainvillea, Acacia, Fluggea, Carissa. roots which grow into plantlets. 7. Support - Example: Passiflora, Example: Millingtonia, Bergera Bougainvillea, Vitis, Cissus koenigii (Murraya koenigii), Coffea quadrangularis. arabica and Aegle marmelos. Foliar buds are those that grow on leaves 3.6.1 Buds from veins or from margins of the Buds are the growing points surrounded leaves. Example: Begonia (Elephant by protective scale leaves. The bud ear plant) and Bryophyllum (Sprout primordium matures into bud. They have leaf plant). Cauline buds arise directly compressed axis in which the internodes from the stem either from cut, pruned are not elongated and the young leaves ends or from branches. Adventitious are closed and crowded. When these buds buds function as propagules which develop, the internodes elongate and the are produced on the stem as tuberous leaves spread out. Buds have architecture structures. Example: Dioscorea, identical to the original shoot and develop Agave. into lateral branches or may terminate by 6. Bulbils (or specialized buds) : developing into a flower or inflorescence. Bulbils are modified and enlarged Based on Origin Buds are classified into bud, meant for propagation. When (a) Terminal or Apical bud (b) Lateral or bulbils detach from parent plant and Axillary or Axil bud. Based on Function fall on the ground, they germinate Buds classified into (a) Vegetative bud into new plants and serve as a means (b) Floral or Reproductive bud of vegetative propagation. In Agave 1. Terminal bud or apical bud: These and Allium proliferum floral buds buds are present at the apex of the main get modified into bulbils. In Lilium stem and at the tips of the branches. bulbiferum and Dioscorea bulbifera, the bulbils develop in axil of leaves. 2. Lateral bud or Axillary bud: These In Oxalis, they develop just above the buds occur in the axil of the leaves and swollen root. develop into a branch or flower.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 71 02-06-2018 13:48:30 3.6.2 Types of Stem 2. Trailers (Stragglers) Majority of angiosperm possess upright, It is a weak stem that spreads over the vertically growing erect stem. They are surface of the ground without rooting (i) Excurrent, (ii) Decurrent, (iii) Caudex, at nodes. They are divided into 3 types, (iv) Culm. i. Prostrate (Procumbent): A stem that i. Excurrent grows flat on the ground. Example: Evolvulus alsinoides, Indigofera The main axis shows continuous growth prostrata. and the lateral branches gradually becoming shorter towards the apex ii. Decumbent: A stem that grows flat but which gives a conical appearance to the becomes erect during reproductive trees. Example: Polyalthia longifolia, stage. Example: Portulaca, Tridax, Casuarina. Lindenbergia ii. Decurrent iii. Diffuse: A trailing stem with spreading The growth of lateral branch is more branches. Example: Boerhaavia vigorous than that of main axis. The tree diffusa, Merremia tridentata has a rounded or spreading appearance. 3. Climbers Example: Mangifera indica, Azadirachta These plants have long weak stem and indica, Tamarindus indicus, Aegle produce special organs for attachment for marmelos climbing over a support. Climbing helps to iii. Caudex display the leaves towards sunlight and to It’s an unbranched, stout, cylindrical position the flower for effective pollination. stem, marked with scars of fallen leaves. i. Root climbers Example: Cocus nucifera, Borassus Plants climbing with the help of flabelliformis, Areca catechu adventitious roots (arise from nodes) as iv. Culm in species of Piper betel, Piper nigrum, Erect stems with distinct nodes and usually Hedera helix, Pothos, Hoya. hollow internodes clasped by leaf sheaths. ii. Stem climbers (twiners) Example: Majority of grasses including These climbers lack specialised structure Bamboo. for climbing and the stem itself coils 3.6.3 Modification of Stem around the support. Example: Ipomoea, Convolvulus, Dolichos, Clitoria, Quisqualis. I. Aerial modification of stem Stem climbers may coil around the 1. Creepers support clockwise or anti-clockwise. These are plants growing closer Clockwise coiling climbers are called (horizontally) to the ground and produces dextrose. Example: Dioscorea alata. Anti- roots at each node. Example: Cynodon clockwise coiling climbers are called dactylon, Oxalis, Centella sinistrose. Example: Dioscorea bulbifera.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 72 02-06-2018 13:48:30 Stem modification

Aerial Sub-Aerial Underground modification modification modification

Runner Stolon Sucker Offset

Creepers Trailer Climber Bulb Corm Rhizome Tuber

Procumbent Root Climber Decumbent Stem Climber (Twiner) Tendril Climber Diffuse Hook climber Lianas

iii. Hook climbers Passiflora, Vitis and Cissus quadrangularis; These plants produce specialized hook Inflorescence axis – Antigonon; Leaf – like structures which are the modification Lathyrus; Leaflets - Pisum sativum; Petiole of various organs of the plant. In – Clematis; Leaftip – Gloriosa; Stipules – Artabotrys inflorescence axis is modified Smilax. In pitcher plant (Nepenthes) the into hook. In calamus (curved hook) leaf midrib of the leaf often coils around a tip is modified into hook. In Bignonia support like a tendril and holds the pitcher unguis-cati the leaflets are modified into in a vertical position. curved hook. In Hugonia the axillary buds Phylloclade modified into hook. This is a green, flattened cylindrical iv. Thorn climbers or angled stem or branch of unlimited Climbing or reclining on the support with growth, consisting of a series of nodes the help of thorns as in Bougainvillea and and internodes at long or short intervals. Carissa. Phylloclade is characteristic adaptation of xerophytes where the leaves often v. Lianas (woody stem climber) fall off early and modified into spines Woody perennial climbers found in tropical or scales to reduce transpiration. The forests are lianas. They twine themselves phylloclade takes over all the functions of around tall trees to get light. Example: leaves, particularly photosynthesis. The Hiptage benghalensis, Bauhinia vahlii, phylloclade is also called as cladophyll. Entada pursaetha. Example: Opuntia, Phyllocactus, Muehlenbergia (flattened phylloclade) vi. Tendril climbers Casuarina, Euphorbia tirucalli, Tendrils are thread-like coiling structures Euphorbia antiquorum (cylindrical which help the plants in climbing. Tendrils phylloclade). may be modifications of Stem – as in

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 73 02-06-2018 13:48:30 Cladode

Runner Phylloclade Scaly leaf Spine Root (a) (a) (b)

Figure 3.8: (a) Phylloclade-Opuntia (b) Cladode-Asparagus

Stolon Cladode

Cladode is a flattened or cylindrical stem Root similar to Phylloclade but with one or two internodes only. Their stem nature (b) is evident by the fact that they bear buds, Figure 3.9: (a) Runner-Oxalis scales and flowers. Example: Asparagus (b) Stolon-Fragaria (cylindrical cladode), Ruscus (flattened 2. Stolon Cladode). This is also a slender, lateralNew branch plant Thorns originating from the base of theRoot stem. But it first grows obliquely above the Thorn is a woody and sharp pointed Sucker ground, produces a loop and bends down modified stem. Either the axillary bud towards the ground. When touches the or the terminal bud gets modified into ground it produces roots and becomes an thorns. In Carissa apical bud modified independent plantlet. Example: Mentha into thorns. In Citrus and Atalantia Offset piperita (peppermint), Fragaria indica (wild axillary bud is modified into thorns. strawberry). II. Sub aerial stem modifications 3. Sucker Root pocket Sub aerial stem found in plants with weak Sucker develops from a underground stem stem in which branches lie horizontally on and grows obliquely upwards and gives rise the ground. These are meant for vegetative to a separate plantlet or new plant. Example: propagation. They may be sub aerial or Chrysanthemum, Musa, Bambusa. partially sub terranean. 4. Offset 1. Runner Offset is similar to runner but found in This is a slender, prostrate branch creeping aquatic plants especially in rosette leaved on the ground and rooting at the nodes. forms. A short thick lateral branch arises Example: Centella (Indian pennywort), from the lower axil and grows horizontally Oxalis (wood sorrel), lawn grass (Cynodon leafless for a short distance, then it dactylon). produces a bunch of rosette leaves and

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 74 02-06-2018 13:48:30 Stolon

root at nodes. Example: EichhorniaRoot (water each other by their margins only. Example: hyacinth), Pistia (water lettuce). Tulipa spp. Pseudobulb is a short erect aerial storage or propagating stem of certain epiphytic and terrestrial sympodial New plant orchids. Example: Bulbophyllum. Root 2. Corm (c) Sucker This is a succulent underground stem with an erect growing tip. The corm is surrounded by scale leaves and exhibit nodes Offset and internodes. Example: Amorphophallus, Gladiolus, Colocasia, Crocus, Colchicum (d) Figure 3.9: (c) Sucker-ChrysanthemumRoot pocke t (d) Offset-Eichhornia III. Underground stem modifications Perennial and some biennial herbs have underground stems, which are generally known as root stocks. Rootstock functions Bulb- Rhizome as a storage and protective organ. It Allium cepa Zingiber officinale remains alive below the ground during unfavourable conditions and resumes growth during the favourable conditions. Underground stems are not roots because they possess nodes, internodes, scale-leaves and buds. Rootstock also lack root cap and root hairs but they possess terminal bud which is a characteristics of stem. Corm-Colocasia Tuber 1. Bulb Solanum tuberosum It is a condensed conical or convex stem Figure 3.10: Underground Stem surrounded by fleshy scale leaves. They are Modification of two types 1. Tunicated (coated) bulb: In 3. Rhizome which the stem is much condensed and surrounded by several concentric layers of This is a underground stem grows scale leaves. The inner scales commonly horizontally with several lateral growing fleshy, the outer ones dry. These are two tips. Rhizome posses conspiquous nodes types (a) Simple Tunicated bulb Example: and internodes covered by scale leaves. Allium cepa (b) Compound Tunicated Example: Zingiber officinale, Canna, bulb. Example: Allium sativum. 2. Scaly Curcuma longa, Maranta arundinacea, bulb: They are narrow, partially overlap Nymphaea, Nelumbo.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 75 02-06-2018 13:48:34 4. Tuber 3. It is exogenous in origin. This is a succulent underground spherical 4. It has limited growth. or globose stem with many embedded 5. It does not posses apical bud. axillary buds called “e y e s ”. Example: 6. It has three main parts namely, leaf Solanum tuberosum, Helianthus tuberosus base, petiole and lamina. IV. Stem Branching 7. Lamina of the leaf is traversed by vascular strands, called veins. Branching pattern is determined by the relative activity of apical meristems. The II. Functions of the leaf mode of arrangement of branches on a Primary functions stem is known as branching. There are 1. Photosynthesis two main types of branching, 1. Lateral 2. Transpiration branching and 2. Dichotomous branching. Based on growth pattern stems may show 3. Gaseous exchange indeterminate or determinate growth. 4. Protection of buds 5. Conduction of water and dissolved 1. Indeterminate: The terminal bud solutes. grows uninterrupted and produce Secondary functions several lateral branches. This type of 1. Storage – Example: Aloe, Agave, growth is also known as monopodial Kalanchoe, Sedum, Brassica oleracea. branching. Example: Polyalthia, 2. Protection – Example: Berberis, Swietenia, Antiaris. Opuntia, Argemone mexicana. 2. Determinate: The terminal bud caese 3. Support – Example: Gloriosa, to grow after a period of growth and the Nepenthes further growth is taken care by successive 4. Reproduction - Example: Bryophyllum, or several lateral meristem or buds. Begonia, Zamioculcas. This type of growth is also known as sympodial branching. Example: Cycas. 3.7.1 Parts of the leaf 3.7 Leaf Three main parts of a typical leaf are: Leaves are green, thin flattened lateral i. Leaf base (Hypopodium) outgrowths of the stem and exogenenous ii. Petiole (Mesopodium) in origin. They arise from the nodes iii. Lamina (Epipodium) of the stem and have limited growth and life span. Leaves are the primary I. Leaf base (hypopodium) photosynthetic organs and the main site The part of the leaf attached to the node of transpiration. All the leaves of a plant of the stem is called leaf base. Usually it together are referred to as phyllome. protects growing buds at its axil. Pulvinus: In legumes leafbase become I. Characteristics of leaf broad, thick and swollen which is known 1. Leaf is a lateral appendage of the stem. as pulvinus. Example: Clitoria, Lablab, 2. It is borne at the node of the stem. Cassia, Erythrina, Butea, Peltophorum.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 76 02-06-2018 13:48:34 numerous lateral veins and thin veinlets. The lamina shows great variations in its shape, margin, surface, texture, colour, venation and incision. Stipules In most of the dicotyledonous plants, the leaf base bears one or two lateral appendages called the stipules. Leaves with stipules are called stipulate. The leaves without stipules are called exstipulate or estipulate. The stipules are commonly found in dicotyledons. In some grasses (Monocots) an additional out growth is Figure 3.11: (a) Parts of the leaf present between leaf base and lamina. It (b) Pulvinus leaf base (c) Sheathing is called Ligule. Sometimes, small stipule leaf base like outgrowths are found at the base of leaflets of a compound leaf. They are Sheathing leafbase: In many monocot called stipels. The main function of the families such as Arecaceae, Musaceae, stipule is to protect the leaf in the bud Zingiberaceae and Poaceae the leafbase condition. extends into a sheath and clasps part or whole of the internode. Such leafbase also 3.7.2 Venation leave permanent scars on the stem when The arrangement of veins and veinlets on they fall. Example: Arecaceae the leaf blade or lamina is called venation. II. Petiole (stipe or mesopodium) Internally, the vein contains vascular It is the bridge between leaf and stem. tissues. Conventionally venation is Petiole or leaf stalk is a cylindrical or sub classified into two types namely, Reticulate cylindrical or flattened structure of a leaf venation and Parallel venation. which joins the lamina with the stem. A I. Reticulate venation leaf with petiole is said to be petiolate. Example: Ficus, Hibiscus, Mangifera, In this type of venation leaf contain a Psidium. Leaves that do not possess petiole prominent midrib from which several is said to be sessile. Example: Calotropis, secondary veins arise that branch and Gloriosa. anastomose like a network. This type of venation is common in all dicot leaves. It III. Lamina (Leaf blade) is of two types. The expanded flat green portion of the 1. Pinnately reticulate venation leaf is the blade or lamina. It is the seat (unicostate): In this type of venation of photosynthesis, gaseous exchange, there is only one midrib in the centre transpiration and most of the metabolic which forms many lateral branches to reactions of the plant. The lamina is form a network. Example: Mangifera traversed by the midrib from which arise indica, Ficus religiosa, Nerium.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 77 02-06-2018 13:48:34 2. Palmately reticulate venation 2. Palmate Parallel Venation (multicostate): In this type of venation (Multicostate) there are two or more principal veins In this type several veins arise from the tip arising from a single point and they of the petiole and they all run parallel to proceed outwards or upwards. The two each other and unite at the apex. It is of types of palmate reticulate venation are two sub types. i. Divergent type: When all principal i. Divergent type: All principal veins veins originate from the base and originate from the base and diverge diverge from one another towards towards the margin, the margin of the leaf the margin of the leaf as in Cucurbita, as in fan palm (Borassus flabelliformis) Luffa, Carica papaya, etc., ii. Convergent type: All principal veins ii. Convergent: When the veins run parallel to each other from the converge to the apex of the leaf, as base of the lamina and join at the apex in Indian plum (Zizyphus), bay leaf as in Bamboos, rice, water hyacinth. (Cinnamomum) Rctcnngn"xgpcvcvkqp

(a) Canna (b) Bamboo (c) Borassus (a) Ficus (b) Cucurbita (c) Cinnamomum Figure 3.13: Types of Parallel venation Figure 3.12: Types of reticulate venation (a) Pinnately parallel venation (a) Pinnately reticulate (b) Palmately parallel(Convergent) (b) Palmately reticulate (Divergent) (c) Palmately parallel (Divergent) (c) Palmately reticulate (Convergent) 3.7.3 Phyllotaxy II. Parallel venation The mode of arrangement of leaves on Veins run parallel to each other and do the stem is known as phyllotaxy (Gk. not form a prominent reticulum. It is a Phyllon = leaf ; taxis = arrangement). characteristic feature of monocot leaves. Phyllotaxy is to avoid over crowding of It is classified into two sub types. leaves and expose the leaves maximum to 1. Pinnately Parallel Venation the sunlight for photosynthesis. The four (Unicostate) main types of phyllotaxy are (1) Alternate When there is a prominent midrib in (2) Opposite (3) Ternate the center, from which arise many veins (4) Whorled. perpendicularly and run parallel to each 1. Alternate other. Example: Musa, Zinger, Curcuma, phyllotaxy Canna. In this type there is only

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 78 02-06-2018 13:48:34 Modern morphologist Hickey (1973) and Hickey and Wolf (1975) classified the venation into following major types based on the pattern of primary, secondary and tertiary venation. • Craspedodromous – In which secondary veins terminate at the leaf margin. (sub types are simplecraspedodromous, semicraspedodromous, mixed craspedodromous). • Camptodromous – In which secondary veins do not terminate at the margin. (sub types are brochidodromous, eucamptodromous, cladodromous, reticulodromous). • Hyphodromous – With only the primary midrib vein present or evident and secondary veins either absent, very reduced or hidden with the leaf mesophyll. • Parallellodromous – Venation is equivalent to parallel in which two or more primary or secondary veins run parallel to one another, converging at the apex. • Actinodromous – If three or more primary veins diverge from one point. • Palinoactinodromous – Similar to actinodromous, but the primary veins have additional branch in above the main point of divergence of the primaries. • Flabellate – Venation is that in which several equal, fine veins branch toward the apex of the leaf. • Campylodromous – Venation is that in which several primary veins run in prominent, recurved arches at the base, curving upward to converge at the leaf apex. • Acrodromous – If two or more primary veins run in convergent arches toward the leaf apex.

one leaf per node and the leaves on the i. Opposite superposed: The pair of successive nodes are arranged alternate leaves arranged in succession are to each other. Spiral arrangement of in the same direction, that is two leaves show vertical rows are called opposite leaves at a node lie exactly orthostichies. They are two types. above those at the lower node. a) Alternate spiral: In which the leaves are Example: Psidium (Guava), Eugenia arranged alternatively in a spiral manner. jambolana (Jamun), Quisqualis Example: Hibiscus, Ficus. (Rangoon creeper). b) Alternate distichous or Bifarious: ii. Opposite decussate: In this type of In which the leaves are organized phyllotaxy one pair of leaves is placed alternatively in two rows on either side of at right angles to the next upper the stem. Example: Monoon longifolium or lower pair of leaves. Example: (polyalthia longifolia). Calotropis, Zinnia, Ocimum 2. Opposite phyllotaxy 3. Ternate phyllotaxy In this type each node possess two leaves In this type there are three leaves attached opposite to each other. They are organized at each node. Example: Nerium in two different types.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 79 02-06-2018 13:48:34 Alternate Opposite Opposite Decussate Ternate Whorled Polyalthia Superposed Guava Calotropis Nerium Allamanda Figure 3.14: Phyllotaxy 4. Whorled (verticillate) type of called leaflets. Compound leaves have phyllotaxy evolved to increase total lamina surface. In this type more than three leaves are There is one axillary bud in the axil of present in a whorl at each node forming the whole compound leaf. The leaflets a circle or whorl. Example: Allamanda, however, do not possess axillary buds. Alstonia scholaris. 1. Pinnately compound leaf 3.7.4 Leaf mosaic A pinnately compound leaf is defined as one in which the rachis, bears laterally a number In leaf mosaic leaves tend to fit in with of leaflets, arranged alternately or in an one another and adjust themselves in such opposite manner, as in tamarind, Cassia. a way that they may secure the maximum i. Unipinnate: The rachis is simple amount of sunlight with minimum and unbranched which bears leaflets amount of overlapping. The lower leaves directly on its sides in alternate or have longer petioles and successive upper opposite manner. Example: Rose, Neem. leaves possess decreasing length petioles. Unipinnate leaves are of two types. Example: Acalypha, Begonia. a. when the leaflets are even in 3.7.5 Leaf type number, the leaf is said to be The pattern of division of a leaf into paripinnate. Example: Tamarind, discrete components or segments is Abrus, Sesbania, Saraca, Cassia. termed leaf type. b. when the leaflets are odd in Based on the number of segments number, the leaf is said to be imparipinnate. Example: Rose, I. Simple leaf Neem (Azadirachta), Chinese box A leaf is said to be simple when the petiole (Murraya). bears a single lamina; lamina may be entire ii. Bipinnate: The primary rachis (undivided) Example: Mango or incised produces secondary rachii which bear to any depth but not upto the midrib or the leaflets. The secondary rachii are petiole. Example: Cucurbita. known as pinnae. Number of pinnae II. Compound leaf varies depending on the species. Example: Delonix, Mimosa, Acacia Compound leaf is one in which the main nilotica, Caesalpinia. rachis bears more than one lamina surface,

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 80 02-06-2018 13:48:35 • Foliage leaves — are ordinary green, flat, lateral appendages of the stem or the branch borne at the node. • Cotyledons or seed leaves — are attached to the axis of the embryo of the seed. As the seed germinates, they usually turn green and become leaf-like. • Cataphylls or scale leaves — are reduced forms of leaves, stalkless and often brownish. They are the bud-scales, scales on the rhizome (underground stems), and also on other parts of the plant body (Bamboo). • Prophylls — the first formed leaves are called prophylls. • Floral leaves — are members of a flower, forming into two accessory whorls (calyx and corolla), two essential whorls(androecium and gynoecium). • Hypsophylls or bract leaves — these leaves cover the flower or an inflorescence in their axil. The main function of these leaves is to protect the flower buds.

iii. Tripinnate: When the rachis branches i. Unifoliolate: When a single leaflet thrice the leaf is called tripinnate. is articulated to the petiole is said to (i.e) the secondary rachii produce the be unifoliolate. Example: Citrus, Des tertiary rachii which bear the leaflets. modium gangeticum. Example: Moringa, Oroxylum. ii. Bifoliolate: When there are two iv. Decompound: When the rachis leaflets articulated to the petiole it of leaf is branched several times it is said to be bifoliolate. Example: is called decompound. Example: Balanites roxburghii, Hardwickia Daucus carota, Coriandrum sativum, binata, Zornia diphylla Foeniculum vulgare. iii. Trifoliolate: There are three leaflets 2. Palmately compound leaf articulated to the petiole it is said to be trifoliolate. Example: wood apple A palmately compound leaf is defined as (Aegle marmelos), Clover (Trifolium), one in which the petiole bears terminally, Lablab, Oxalis one or more leaflets which seem to be radiating from a common point like iv. Quadrifoliolate: There are four fingers from the palm. leaflets articulated to the petiole it is

(a) (b) (c) (d) (e) Figure 3.15: Types of pinnately compound leaves (a) Unipinnate (Paripinnate)-Tamarindus (b) Unipinnate (Imparipinnate)-Azadirachta (c) Bipinnate-Caesalpinia (d) Tripinnate-Moringa (e) Decompound-Coriandrum

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 81 02-06-2018 13:48:35 (a) (b) (c) (d) (e) Figure 3.16: Types of palmately compound leaves (a) Unifoliolate - Citrus (b) Bifoliolate – Zornia (c) Trifoliolate – Aegle marmelos (d) Quadrifoliolate – Paris quadrifolia (e) Multifoliolate – Bombax

said to be quadrifoliolate. Example: elegant climber, the terminal leaflets become Paris quadrifolia, Marsilia modified into three, very sharp, stiff and v. Multifoliolate or digitate: Five or curved hooks, very much like the nails of a more leaflets are joined and spread cat. These hooks cling to the bark of a tree and like fingers from the palm, as in act as organs of support for climbing. The leaf silk cotton tree, Cleome pentaphylla, spines of Asparagus also act as hooks. Bombax ceiba

3.7.6 Modification of Leaf Spines (Zizyphus) The main function of the leaf is food Tendrils Hooks preparation by photosynthesis. Leaves (Pisum) (Bignonia) also modified to perform some specialized functions. They are described below. Floral Leaf I. Leaf tendrils Leaf leaves blader modifi cations In some plants Stem is very weak and (Delonix) (Utricularia) hence they have some special organs for attachment to the support. So some leaves Storage Phyllode are partially or wholly modified into leaves (Acacia) tendril. Tendril is a slender wiry coiled Pitcher (Aloe) structure which helps in climbing the (Nepenthes) support. Some of the modification of leaf tendrils are given below: Entire leaf—Lathyrus, stipules—Smilax, III. Leaf Spines and Prickles terminal leaflet—Naravelia, Leaf tip— Leaves of certain plants develop spinesent Gloriosa, Apical leaflet—Pisum, petiole— structures. Either on the surface or on the Clematis. margins as an adaptation to herbivory and xeric conditions. Example: Argemone mexicana II. Leaf hooks (Prickly poppy), Solanum trilobatum, Solanum In some plants, leaves are modified into virginianum. In xerophytes such as Opuntia hook-like structures and help the plant to (Prickly pear) and Euphorbia leaves and stipules climb. In cat,s nail (Bignonia unguis-cati) an are modifi ed into spines.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 82 02-06-2018 13:48:45 Prickles are small, sharp structure pitcher the mouth of the pitcher is closed by which are the outgrowths from epidermal a lid which is the modification of leaf apex. cells of stem or leaf. It helps the plant in VII. Bladder scrambling over other plants. It is also protective against herbivory. Example: In bladderwort (Utricularia), a rootless Rosa spp, Rubus spp. free-floating or slightly submerged plant common in many water bodies, IV. Storage Leaves the leaf is very much segmented. Some Some plants of saline and xerophytic habitats of these segments are modified to form and members of the family Crassulaceae bladder-like structures, with a trap-door commonly have fleshy or swollen leaves. entrance that traps aquatic animalcules. These succulent leaves store water, mucilage VIII Floral leaves or food material. Such storage leaves resist desiccation. Example: Aloe, Agave, Floral parts such as sepals, petals, stamens and Bryophyllum, Kalanchoe, Sedum, Sueada, carpels are modified leaves. Sepals and petals Brassica oleracea (cabbage-variety capitata). are leafy. They are protective in function and considered non-essential reproductive parts. V. Phyllode Petals are usually coloured which attract the Phyllodes are flat, green-coloured leaf- insects for pollination. Stamens are considered like modifications of petioles or rachis. pollen bearing microsporophylls and carpels The leaflets or lamina of the leaf are highly are ovule bearing megasporophylls. reduced or caducous. The phyllodes perform 3.7.7 Ptyxis photosynthesis and other functions of leaf. Example: Acacia auriculiformis (Australian Rolling or folding of individual leaves may Acacia), Parkinsonia. be as follows: 1. Reclinate - when the upper half of the VI. Pitcher leaf blade is bent upon the lower half The leaf becomes modified into a pitcher in as in loquat (Eriobotrya japonica). Nepenthes and Sarracenia. In Nepenthes the 2. Conduplicate - when the leaf is folded basal part of the leaf is laminar and the midrib lengthwise along the mid-rib, as in continues as a coiled tendrillar structure. guava, sweet potato and camel’s foot The apical part of the leaf as modified into a tree (Bauhinia).

Leaf hooks-Bignonia Leaf spines- Zizyphus Phyllode-Acacia Pitcher-Nepenthes Figure 3.17: Leaf Modification

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 83 02-06-2018 13:48:45 3. Plicate or plaited – when the leaf is 3.7.9 Leaf symmetry repeatedly folded longitudinally along 1. Dorsiventral leaf ribs in a zig-zag manner, as in Borassus flabellifer. When the leaf is flat, with the blade placed horizontally, showing a distinct upper 4. Circinate - when the leaf is rolled from surface and a lower surface, as in most the apex towards the base like the tail dicotyledons, it is said to be dorsiventral. of a dog, as in ferns. Example: Tridax. 5. Convolute - when the leaf is rolled from one margin to the other, as in 2. Isobilateral leaf banana, aroids and Indian pennywort. When the leaf is directed vertically Musa and members of Araceae. upwards, as in many monocotyledons, it is 6. Involute - when the two margins are said to be isobilateral leaf. Example: Grass. rolled on the upper surface of the leaf 3. Centric leaf towards the midrib or the centre of the leaf, as in water lily, lotus, Sandwich When the leaf is more or less cylindrical and Island Climber (Antigonon) and directed upwards or downwards, as in pine, Plumbago. onion, etc., the leaf is said to be centric. 7. Crumpled - when the leaf is irregularly 4. Heterophylly folded as in cabbage. Occurrence of two different kinds of leaves 3.7.8 Leaf duration in the same plant is called heterophylly. Heterophylly is found in many aquatic Leaves may stay and function for few days plants. Here, the floating or aerial leaves and to many years, largely determined by the the submerged leaves are of different kinds. adaptations to climatic conditions. The former are generally broad, often fully Cauducuous (Fagacious) expanded, and undivided or merely lobed, Falling off soon after formation. Example: while the latter are narrow, ribbon-shaped, Opuntia, Cissus quadrangularis. linear or much dissected. Heterophylly in water plants is, thus, an adaptation to two different Deciduous conditions of the environment. Example: Falling at the end of growing season so water crowfoot (Ranunculus aquatilis), that the plant (tree or shrub) is leafless in water plantain (Alisma plantago), arrowhead winter/summer season. Example: Maple, (Sagittaria), Limnophila heterophylla. Plumeria, Launea, Erythrina. Terrestrial (land) plants also exhibit this Evergreen phenomenon. Among them Sterculia villosa, jack (in early stages), Ficus heterophylla show Leaves persist throughout the year, falling leaves varying from entire to variously lobed regularly so that tree is never leafless. structures during different developmental Example: Mimusops, Calophyllum. stages. Young leaves are usually lobed or Marcescent dissected and the mature leaves are entire. Such Leaves not falling but withering on the type is known as developmental heterophylly. plant as in several members of Fagaceae. Example: Eucalyptus, Artocarpus heterophyllus.

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 84 02-06-2018 13:48:45 Summary Evaluation Flowering plants consist of two major organ 1. Roots are systems: Underground root system and aerial a. Descending, root system. Roots perform the functions of negatively anchoring and absorbing nutrients from the geotropic, positively soil. However some roots perform additional phototropic functions for which they undergo various b. Descending, positively geotropic, modifications in shape, form and structure. negatively phototropic Tap root continue the growth from the radical c. Ascending, positively geotropic, which further branches into secondary roots. negatively phototropic Adventitious roots arise from different parts d. Ascending, negatively geotropic, of the plant other than radical. Stem helps to positively phototropic display the leaves to get maximum sunlight and positioning flowers and fruits to attract 2. When the root is thick and fleshy, but pollination and dispersal agents. Apart from does not take a definite shape, it said to be the normal functions the stems are modified a. Nodulose root to perform various functions such as food b. Tubercular root storage, perennation and protection. Leaves c. Moniliform root are exogenous in origin and function as food d. Fasciculated root synthesizing and gaseous exchange sites. Some 3. Example for negatively geotropic roots leaves also perform additional functions for which they are modified in their morphology. a. Ipomoea, Dahlia Leaves possess vascular tissues in the form of b. Asparagus, Ruellia veins which render support to the lamina and c. Vitis, Portulaca help in transport of water, nutrients and food in d. Avicennia, Rhizophora and out of leaves. Phyllotaxy is the arrangement 4. Curcuma amada, Curcuma domestica, or distribution of leaves on the stem or its Asparagus, Maranta are example of branches in such a way that they receive maximum sunlight to perform photosynthesis. a. Tuberous root b. Beaded root Activity c. Moniliform root 1. Collection of medicines prepared d. Nodulose root from root, stem, leaf of organic plants. 5. Bryophyllum and Dioscorea are example for 2. Prepare a report of traditional a. Foliar bud, apical bud medicines. b. Foliar bud, cauline bud 3. Classroom level exhibition on c. Cauline bud, apical bud Siddha and Ayurvedic medicine d. Cauline bud, foliar bud prepared from root, leaf, stem. 6. Why lateral roots are endogenous? 4. Growing micro greens in class room – project work. (Green seed sprouts)

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TN_GOVT_BOTANY_XI_Page 063-086 CH03.indd 85 02-06-2018 13:48:45 7. Write the similarities and differences 8. How root climbers differ from stem between climbers? 1. Avicennia and Trapa 9. Compare sympodial branching with 2. Banyan and silk cotton monopodial branching. 3. Fusiform and Napiform root 10. Compare pinnate unicostate and palmate multicostate venation?

ICT Corner

Monocot and Dicot plants

Is plants differ morphologically?

Steps • Scan the QR code or go to google play store • Type online labs and install it. • Select biology and select Characteristics of plants • Click theory to know the basic about Characteristics of plants • Register yourself with mail-id and create password to access online lab simulations

Activity • Select video and record your observations of different forms of plant group.

Step 1 Step 2 Step 3 Step 4

URL:

https://play.google.com/store/apps/details?id=in.edu.olabs.olabs&hl=en

* Pictures are indicative only

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