Resolving taxonomic problems in the genus Ceropegia L. (Apocynaceae: Asclepiadoideae) with vegetative micromorphology

Abstract

The genus Ceropegia L. of Family Apocynaceae, subfamily Asclepiadoideae comprises 213 accepted taxa distributed in tropical and sub-tropical regions of Africa, India, Australia and neighbouring regions. The taxa are mainly identified on the basis of flower morphology. A study was undertaken to reveal micromorphology of 26 taxa distributed in Western Ghats of India to solve the identity problems. The micromorphology is studied with standard microscopic methods in five replicates of each character and taxa to reveal the parameters, distribution of stomata, stomatal index, stomatal density, epidermal cell wall pattern and stomatal measurements. The data obtained was subjected to ANOVA to find out the experimental mean, standard deviation and standard error. A consensus phylogeny tree is constructed using the PAST on the basis of Jaccard similarity coefficient. Results of study revealed that, micro morphological characters, viz., type of stomata, number and characters of subsidiaries, anticlinal cell wall pattern, and stomatal index are very significant in delimitation of closely allied taxa. Beside ‘paracytic’ stomata, ‘tetracytic’, ‘isotricytic’, & ‘anomocytic’ stomatal types, and amphistomatic distribution are recorded for first time in Ceropegia. The taxa are separated easily from each other using vegetative micromorphology and can be identified even in absence of flowers. An identification key and phylogenetic tree is derived on the basis of vegetative micro-morphology and gross morphological characters.