Morphological and histological study of trichomes in six Nepeta species by light and scanning electron microscopy

Aim: in the present study, morphology and also histology of six Nepeta species were investigated.
Material and six species of the genus were collected from different parts of Iran. From each species, one population and from each populations three flowering stems were randomly elected. The mature intact leaf of each sample was fixed in FAA solution, and then transverse hand sections of them were double stained and examined under light microscopy. For scanning electron microscopy, a small part of leaves were coated with gold then, samples transferred to SEM for taking micrograph. The used software was SPSS.
Thirteen glandular and non-glandular trichomes were observed in the studied species. The morphology and density of trichomes varied between species and ANOVA test showed significant differences in some trichome types between the studied species. The peltate and capitate were the most important glandular trichomes. In addition, non- glandular hairs were existed in two forms: branched and non-branches. The branched ones were found in only one species.
on the basis of variations in glandular trichomes, it is expected that the amount of essential oil is variable between the studied species. In addition, the abilities of species are different in maintenance of essential oil. Moreover, the trichomes can use a good trait for improvement of Nepeta taxonomy.