Comparative epidermal and trichome analysis in the genus Acmella

Epidermal studies in nine taxa of genus Acmella were carried out with a view to identify epidermal characters of taxonomic values. The study also focuses on the type of trichomes present in various parts of plant species. Data obtained were subjected to descriptive statistical analysis. Epidermal characters studied include trichome types, presence and absence of stomata and values of the stomatal index which are valuable in delimiting the species. The overall results showed overlaps in the quantitative attributes of the Acmella taxa studied suggesting that they belong to the same genus. The length of stomata varied from 14.12 - 23.61µm and the highest length was observed in Acmella ciliata, A. vazhachalensis and A. calva and the lowest in A. uliginosa. The width of stomata ranged from 2.47- 4.51µm; A. uliginosa had the highest stomatal width and A. calva, the lowest. A. calva possess highest stomatal index and A. vazhachalensis have lowest. Presence of anisocytic, diacytic or anomocytic stomata were of diagnostic important in the nine taxa. Non glandular trichomes were distributed in leaves, petioles, peduncle, stem, involucre bract, ray florets and in palea. No significant trichome variations were noticed among the taxa to discriminate it.