Exploring the taxonomic relevance: foliar epidermal microanatomy of aromatic and medicinal plants within subfamily Nepetoideae

The micromorphology of epidermal cells, different types of trichomes, and stomatal complex were used to describe leaf epidermal traits. Light microscopy (LM) and scanning electron microscopy (SEM) were used to thoroughly analyze the foliar anatomical features of 33 taxa of aromatic and medicinal plants of sub family Nepetoideae. To accurately identify the subfamily taxa, the present study evaluates the leaf anatomical characteristics. The statistical data were used for better understanding the results. The qualitative characters for example, epidermal cells are mostly irregular and polygonal. Aromatic essential oils, saponins, organic acids and tannins are the medical constituents of the Nepetoideae. The highest epidermal cell length at adaxial surfaces was found in Ocimum basilicum (102 µm). Four types of stomata were examined; i.e., anomocytic, diacytic anisocytic and paracytic. The largest stomata length at abaxial surface was observed in Mentha × piperita (39 µm). In the current study, non-glandular trichomes (NGTs) and glandular trichomes (GTs) were investigated. NGTs were mostly branched, unicellular- multicellular with long falcate, short hook, conical and clavate. GTs were divided into sessile and sub sessile capitate and large peltate. Using SEM and LM, significant variation was found in both quantitative and qualitative traits. Unique ornamentation was seen in the variety of trichomes. Unweighted pair group method with arithmetic mean (UPGMA) cluster analysis and principal component analysis were used to describe, depict, and compare the quantitative foliar anatomical characters of all the species. A dichotomous key has been created for rapid and simple identification using qualitative characteristics. The current research adds to the systematic approach by accurately identifying Nepetoideae taxa and employing foliar anatomical traits.