Scanning electron microscopic screening of 20 medicinally important Asteroideae taxa.

In the present study anatomical characterization of 20 medicinally important Asteroideae species were done under light and scanning electron microscopy. Variety of qualitative and quantitative anatomical characters like epidermal cells, stomata, guard cells, subsidiary cells, trichomes and oil droplets were observed. Generally pentagonal, polygonal, irregular or hexagonal, smooth, undulating thick walled epidermal cells were observed in studied species. In abaxial surface Thymophylla tenuiloba L. possessed the largest length of epidermal cell that is, 221.6 (156.6-286.6) μm whereas Bellis perenis L. showed the smallest length that is, 46.4 (32.6-60.2) μm. Average width of epidermal cells ranged from 57 (22-92) μm to 169 (127.9-210.1) μm. Cosmos sulphureus Cav. had smallest width while Thymophylla tenuiloba L. had the largest width. In adaxial surface Artemisia absinthium L. possessed the largest length of epidermal cell that is, 269 (165.1-372.9) μm whereas Bellis perenis L. showed the smallest length that is, 61.4 (42.6-80.2) μm. Average width of epidermal cells ranged from 50.8 (32.6-69) μm to 260 (116-202) μm. Thymophylla tenuiloba L. had smallest width while Dahlia pinnata Cav. had the largest width. Among stomatal characters anisocytic, anomocytic, and diacytic stomata were observed in selected species of Asteroideae. Nonglandular uniserate, multicellular, unbranched pointed tips with bulbous base trichomes were reported in some Asteroideae members while some possessed glandular, capitates mushroom like multicellular trichomes covered with tubercle papicles. Rounded, oval, triangular shaped oil droplets were observed in some species. It is concluded that qualitative and qualitative anatomical variations in trichomes, stomata and epidermal cells are of good taxonomic value for the Asteroideae species.