Comparative morpho-anatomical studies on five species of Ocimum L. leaves

The genus Ocimum (Lamiaceae) comprises several economically and medicinally significant aromatic herbs. This study investigates the comparative morpho-anatomy of leaves from five Ocimum species O. americanum, O. basilicum, O. gratissimum, O. kilimandscharicum and O. tenuiflorum to explore diagnostic features for species differentiation and taxonomic relationships. A detailed analysis of morphological traits (leaf shape, apex, margin and venation) and anatomical features (epidermal structure, stomatal type and index, mesophyll organization, trichome type and distribution) was performed using standard microscopic techniques. Quantitative and qualitative data were compiled into a character matrix, and a cluster analysis was conducted using the UPGMA algorithm to construct a dendrogram illustrating species distance based character relationships on morpho-anatomical similarity. The dendrogram revealed three major clusters, indicating close affinity between O. basilicum and O. americanum, while O. kilimandscharicum formed a distinct group due to its unique anatomical features. The study highlights that trichome morphology and mesophyll differentiation are key traits for distinguishing Ocimum species. The application of UPGMA clustering based on morpho-anatomical data proved effective in elucidating phenetic relationships and supports the use of integrated morpho-anatomical and statistical approaches in plant systematics.