Micromorphological evaluation of the foliar trichomes of field grown and micropropagated Stachys natalensis Hochst. (Lamiaceae)

Abstract

Stachys natalensis Hochst is a perennial shrub with aromatic leaves that are covered with hairs. Micromorphological features of the leaf secretory structures were evaluated using scanning electron microscopy. Glandular and non-glandular trichomes were present on the adaxial and abaxial foliar surfaces of field grown and micropropagated plants. Greater trichome distribution was observed on the abaxial surface, decreasing as the leaf developed (P < 0.05). Micropropagated plants did not show gross morphological abnormalities compared to field-grown plants, apart from the presence of visibly longer non-glandular trichomes. Foliar peltate and capitate glandular trichomes identified across most developmental stages were morphologically similar between micropropagated and field grown plants. This study shows that the mass in vitro propagation of the species, as a means of mitigating declining numbers in the wild, does not compromise trichome morphology or distribution.