AN-APPROACH-TOWARDS-SYTEMATIC-STUDIES-OF-MEGHALAYAN-DIOSCOREA-DIOSCOREACEAE-NORTH-EAST-INDIA-5-1

An Approach Towards Sytematic Studies Of Meghalayan Dioscorea (Dioscoreaceae), North East India

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by Nilofer Sheikh(Author),Yogendra Kumar(Author)

ISBN Number : 978 – 1- 73038 – 448 – 6

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Description

Nilofer Sheikh

c/o Taxonomy Laboratory, North Eastern Hill University Shillong-22

Yogendra Kumar

c/o Taxonomy Laboratory, North Eastern Hill University Shillong-22

Dioscorea L., the largest genus of the family Dioscoreaceae included about 600 species (Coursey, 1967) with about 70 sections mainly distributed in Southeast Asia, Africa, Central America, South America and other tropical or subtropical regions. The family Dioscoreaceae is considered as the most primitive monocots because of its morphological characteristics that resembles similar to the paleoherb dicots (the fossil recorded of the Dioscoreales appears to extent back into the upper Cretaceous) such as presence of reticulated venation and heartshaped or highly lobed leaves (Dahglian, 1981). Hence this family is regarded as the pivotal taxon in the evolution of monocotyledonae and occupies a basal position among all extant monocotyledonous plants (Dahlgren, 1989; Chase et al., 2006). The family Dioscoreaceae has been separated by numerous authors into several allied families. The latest circumscriptions were given by Caddick et al. (2002a and 2002b) with four genera: Dioscorea L., Stenomeris Planch., Tacca and Trichopus Gaertn. (including Aventra). Morphological and molecular evidences proved that these genera formed a strong monophyletic group within the family. Under the previous circumscriptions (Table 1) Dioscorea was paraphyletic with Epipetrum Phil., Nanarepenta Matuda, Rajania L., Tamus L. and also Dioscorea sylvatica, D.elephantipes (Testudinaria Uline), and D.pyrenaica (Borderea Miegev).