Insight into the structure and chemistry of glandular trichomes of selected Micromeria and closely related Clinopodium species (Lamiaceae): the in vitro culture approach

Abstract

Many of the species belonging to the Lamiaceae family are considered aromatic plants due to the presence of glandular trichomes, which have a distinct ability to synthesize, secrete or store large amounts of specialized metabolites that play a crucial role in mediating the plant–environment interactions. Secondary metabolites are biosynthesized as a defensive strategy of plants in response to natural perturbations, thus enabling them to adapt to the environmental stresses typical of each individual ecological niche. These compounds often have marked bioactive properties, rendering a commercial value to the plants that produce them. A number of biological effects have been associated with the main monoterpenoids detected in investigated Micromeria spp. and Clinopodium spp. essential oils. One alternative for the production of these bioactive metabolites is in vitro plant tissue culture. The present study was initiated to investigate the effects of in vitro culture on the secretion of leaf glandular trichomes, the main structures involved in the essential oil production. The glandular indumentum was studied by means of light microscopy and scanning electron microscopy in an attempt to correlate the phytochemical traits with the glandular trichome morphotypes of selected Lamiaceae species.