Glandular Trichomes of Artemisia campestris (ssp. Maritima): Ontogeny and Histochemistry of the Secretory Product

Abstract

The glandular trichomes of Artemisia campestris (ssp. maritima) originate from a single protodermal cell and develop through an anticlinal and several periclinal divisions. These multicellular and biseriate trichomes have a secretory head with three pairs of cells, two stalk cells, and two basal cells. The number of glandular trichomes is established early during leaf differentiation; thus, gland density decreases with leaf development. Oleoresin production begins as soon as the glandular trichomes are fully developed. The main components of the oleoresin are terpenoids (mono- and sesquiterpenes and probably steroids), fatty acids, flavonoids as free aglycones, hydroxycoumarins, and alkaloids. The oleoresin accumulates in the subcuticular space and is released over the leaf blade by rupture of the cuticle.