Micromorphology of glandular trichomes of Nepeta congesta Fisch. & Mey. var. congesta (Lamiaceae) and chemical analysis of the essential oils

The micromorphology and distribution of foliar trichomes of Nepeta congesta var. congesta (Lamiaceae), a species endemic to Turkey, were investigated in order to evaluate the usefulness of this feature for systematic purpose. The aerial parts of N. congesta var. congesta bear an indumentum of glandular and non-glandular trichomes. Two types of glandular trichomes are identified. Peltate trichomes consist of a basal cell embedded in the epidermis, a stalk cell, and a four-celled secretory head. Capitate trichomes comprise either a unicellular head and uni- or bicellular stalk, or a bicellular head and unicellular stalk. Water-distilled essential oil of the aerial parts of N. congesta var. congesta was analysed by GC and GC/MS and the main components were found to be 1.8-cineole (29.9%), germacrene-D (20.3%) and sabinene (10.3%).