Taxonomic significance of Cyspsela in Vernonia anthelmintica Willd. and V. cinerea Less. (Asteraceae; tribe - Vernonieae): Structural manifestations

An investigation was carried out to reveal the taxonomic importance of cypselar features of Vernonia anthelmintica Willd. and Vernonia cinerea Less. through morpho-anatomical manifestations in the plesiomorphic tribe Vernonieae of the dicot family Asteraceae. A light microscopic (LM) and Scanning Electron Microscopic (SEM) study unraveled various morphological features of the cypsela. Among them, apical part, wall surface, surface hairs, nature, structure and arrangement of carpopodium, and stylopodium are taxonomically important traits. Furthermore, presence or absence of glands in wall surface, pappus bristles, testal nature, distribution of crystal and in pericarp and/or testa and endosperms of cypselas can also be considered as taxonomically significant. Distinct differences were observed between two taxa for many characteristics. Notable among these were occurrence of stylopodium, size of cypsela (without pappus), nature of pappus, thickness of pericarp, presence or absence of ribs, layer of radially elongated cells in mesocarpic sclerenchyma ans parenchyma, presence of additional uniseriate palisade like sclerenchymatous layer in V. anthelmintica, but not in V. cinerea, testal epidermal layer, nature of endosperm layer, and crystal formation. Similarities between two taxa were also noted. Based on structural manifestations of cypsela at morpho-anatomical levels, an indented dichotomous key is provided for identification of studied taxa.