Leaf epidermal and petiole anatomical features as taxonomic characters in some Vernonia species in Nigeria

Abstract

Foliar and petiole micro-morphological characteristics of some members of the genus Vernonia namely; Vernonia amygdalina Del. (bitter variety), Vernonia amygdalina Del. (non-bitter variety), Vernonia cinerea (L) Less., Vernonia galamensis (Cass.) Less., and Vernonia adoensis Sch. Bip. in Jos, Nigeria was investigated to provide additional micro-morphological characters to support existing taxonomic information regarding the species. Epidermal peels of fresh leaves were made and transverse sections of petioles were cut using a rotary microtome. Staining was done using Safranin and slides observed using a light microscope. Quantitative characters were measured and subjected to Duncan Multiple Range Test. Stomatal distribution was amphistomatic except for V. galamensis and V. cinerea with hypostomatic distribution; stomata type was mostly anomocytic except V. galamensis with paracytic stomata. Stomata index varied among taxa with V. adoensis and V. amygdalina (bitter variety) having the highest (10.84 %) and lowest (0.67%) respectively. Anticlinal cell wall patterns were straight to slightly undulate while wavy anticlinal cell wall pattern was diagnostic to V. cinerea. Trichome types observed were glandular and multicellular uniseriate with highest and lowest trichome indices recorded in V. adoensis (2.80%) and V. galamensis (0.02%) respectively. Petiole outline was convex to concave, epidermis was uniseriate, trichome multicellular uniseriate and vascular bundles bicollateral. Variations observed in the stomatal complex, epidermal cell complex, petiole outline, petiole vasculature type, trichome and stomata indices could be employed for species identification and delimitation.