Trichome micromorphology of the genus Stachys sect. Fragilicaulis subsect. Fragilis and its taxonomic implications

Abstract The leaf, stem, calyx, and corolla indumentum of seven endemic taxa belonging to Stachys subsect. Fragiles, growing in Turkey, were micromorphologically and anatomically analyzed under scanning electron and light microscopes with the use of cluster analysis and Principal Component Analysis. We detected 10 trichome types on the leaf, seven trichome types on the stem and calyx, and eight trichome types on the corolla. Especially, the type and distribution of the trichomes on the calyx and corolla surfaces were quite different. The calyx and corolla had seven and eight trichome types, including glandular or non-glandular, in the examined taxa, respectively. The most common type observed was a short clavate glandular trichome; however, conical thin-walled unicellular hairs were specific for the studied taxa. No branched trichomes were observed. In the examined taxa, the indumentum indicated variations and some important similarities. The indumentum types have a high taxonomical value for the species of the genus. A key has been offered for the identification of the studied taxa based on the trichome characters, by comparing the key of classic taxonomic characters.