South Indian Journal Of Biological Sciences 2016; 2(1); 115‐118 ONLINE ISSN: 2454‐4787

Research Article

Anatomical studies of selected species of L. in Kerala

Resmi S1*, Thomas VP 2, Sreenivas VK 3

1Department of Botany, University of Calicut, Calicut University P.O., Kerala‐ 673 635, India

2Department of Botany, Catholicate College, Pathanamthitta, Kerala‐ 689 645, India

3Sree Vyasa NSS College, Wadakkancherry, Thrissur, Kerala, India

* Corresponding author: Resmi S; E‐mail: resmischandran [email protected]

Received 2 July 2015; Revised 1 September 2015; Accepted 21 September 2015; Published 2 January 2016

Abstract In the field of vascular anatomy of it is necessary to study the successive stages through which the passes during its development. This procedure not only determines the position, interrelationship and structure of the different vascular components of the mature fern but also shows indications of phylogenetic relationship. For understanding the anatomical features of three species of Adiantum L., stipe of Adiantum caudatum L., Adiantum latifolium Lam. and Adiantum lunulatum Burm., from Kerala were studied. The patterns formed by the protoxylem strands are surprisingly variable among species. A separate key was prepared for the identification of species based on anatomy.

Keywords: Pteridophytes, , Anatomy, Stipe, Adiantum, Kerala

1. Introduction The Pteridophytes are considered to be the primitive vascular group which are scattered all over the world. More than 1200 species of ferns and fern allies have been reported from India. Fern taxonomists have long employed the characteristics of the rhizome, indusium, sporangia and spores in their construction of the systematic treatments of various fern taxa. Leaf characters like venation pattern, trichomes, epidermis and ontogeny of stomata have also been utilized for taxonomic purposes. Likewise, stipe characters have also proved to be of great value (Lucansky and White 1974; Srivastava 2008a, 2008b). By combining the morphological and anatomical features of each species in each family, identification process becomes easier with the more available data provided to distinguish each species (Maideen et al., 2013). However, the characteristics of the stipe still remain to be studied in the case of a number of fern species. With the same view point the anatomical features of the stipe of three Adiantum species from Kerala have been investigated.

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2. Materials and methods 2.1. Collection and investigation of plant materials Plant materials of Adiantum for anatomical investigation were collected from different parts of the Kerala as a part of a taxonomic study of Pteridophytes. The dried specimens were mounted on herbarium sheets and labeled properly after including all the relevant information. The specimens were deposited in the herbarium of St. Thomas College, Thrissur. The identity of the taxon was confirmed with materials deposited at CALI and KFRI. For understanding the anatomical features, stipe of Adiantum caudatum, A. latifolium and A. lunulatum were fixed in FAA and sectioned, stained with safranine and photographed. The following details were observed.

3. Results and discussion 3.1. Anatomy of Adiantum caudatum L. In a transverse section of the stipe shows outer epidermis appear thick walled, single layered with cuticle and dark brown in colour. Numerous long hairs are present on the epidermis. Epidermis is followed by outer 3‐4 layered sclerenchymatous cells and many layered, thin walled, parenchymatous cells with rich tannin content which constitute the ground tissue. Vascular strand is seen at the centre and enclosed by a unilayered pericycle followed by a single layered, thick walled endodermis. The vascular strand represents two xylem groups; one is large and semi‐lunar in shape and is diarch and exarch. Another small patch of xylem is also observed. The xylem is surroundded by the phloem (Plate 01 A).

3.2. Adiantum latifolium Lam. T. S. of petiole shows outer thick walled epidermis which is single layered, cuticularised and brown in colour. Ground tissue is formed of outer 5‐7 layered sclerenchymatous cells followed by inner 6‐7 layered parenchymatous cells with tannin contents. The ground tissue is delimited by a single layered, thick walled endodermis followed by unilayered pericycle. Stipe receives a central vascular strand and the xylem is triarch and exarch. The xylem is arranged like the ‘skull of a bison’; two groups of protoxylem are arraged near the ‘horns’ and one group at the base; metaxylem seen at the centre; xylem is surrounded by the phloem (Plate 01 C).

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3.3. Adiantum lunulatum Burm. The outline of stipe is more or less circular and the outer epidermis is thick walled, single layered with cuticle and is dark brown in colour. The ground tissue is formed of outer 3‐4 layered sclerenchymatous cells followed by thin walled parenchymatous cells with rich tannin content. Endodermis is single layered, formed of thickwalled cells followed by a unilayered pericycle. The xylem is diarch, exarch and is arranged in a V‐shaped manner. The two arms are more turned inwards. The metaxylem seen towards the centre and protoxylem arranged on the arms. The xylem is surrounded by the phloem (Plate 01 B).

3.4. Key to the species 1a. Xylem triarch, arranged like a ‘bison skull’………...... Adiantum latifolium 1b. Xylem diarch, not arranged like a ‘bison skull’………………………………....…2 2a. Xylem arranged in semilunar shape ……………………………………...A. caudatum 2b. Xylem arranged in V‐shape with curved end...………….…………..…A.lunulatum Stipe anatomical features were reported to be suitable for the systematic study of ferns because of the variations in shape of steles and the presence of sclerenchyma (Bidin and Anita 1995; Bidin and Masturi 1996; Ogura 1972). Each species is proved to have distinct stipe anatomical characteristics and hence that can be used to separate different species. Problems in species identification is due to the similarities in morphological characteristics could be solved using anatomical characteristics. Cuticle is present in almost all species of under studied. Presence of well‐developed cuticle is an adaptation to terrestrial habitat. Ferns would be more vulnerable to desiccation if it were not for the presence of a water barrier in the form of an external coating. Cuticle contains hydrophobic materials, secreted by the epidermal cells and forms an almost continuous coating over the entire outer surface of ferns. Development of stomata and of an intercellular air space system insured aeration of the tissue and gas exchange with the external environment. The unrestricted water loss through stomata can be detrimental to the survival of the plant (White 1984). Thus stomata is rare or totally absent in the stipe of three species of Adiantum. In three species of Adiantum under present study, T.S of stipe shows outer sclerenchymatous and inner parenchymatousground tissue. Tannin cells are clearly seen in the ground tissue of Adiantum caudatum, A. latifolium, A. lunulatum. In A. lunulatum xylem is arranged in V‐ shaped manner. Where as in A. caudatum it is semi‐lunarshaped and in A. latifolium xylem is arranged like the skull of a bison and two groups of protoxylem are arranged near the ‘horns’ and one group at the base. Stele shape and size of the upper part and the lower part of the stipes belongs to the same species are found to be variable in some species. 4. Conclusion Variations in the stipe anatomy of three species of Adiantum L. in Kerala have been studied and documented. Characters used include the distribution of sclerenchymatous and parenchymatous cells, shape of vascular bundles and the xylem configuration. In A. caudatum xylem is arranged in a semi‐ lunar shape and in A. lunulatum it is in a V‐ shaped manner whereas in A. latifolium xylem is arranged like the skull of a bison with two groups of protoxylem arranged near the ‘horns’ and one group at the base. The study reveals that there is a gradual change in xylem configurations from the simple to the more complex forms. Xylem arrangement is very helpful in delimiting various species of Adiantum. The 117

patterns formed by the protoxylem strands in the shoot are surprisingly variable among different species. These different patterns are potentially significant both morphologically and systematically.

Conflict of interest statement We declare that we have no conflict of interest.

Acknowledgements We are thankful to the Head, Department of Botany, St. Thomas college, Thrissur for facilities; the librarian and other staff members of St. Thomas college Library, librarian of the Dept. of Botany, Kerala Agriculture University, Mannuthy, the librarian, University of Calicut and the Curator, Calicut University herbarium for the facilities extended to us for completing the work.

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