The morphology and ultrastructure of glandular and non-glandular trichomes of Pteronia incana (Asteraceae)

Abstract

The electron microscopical investigation of foliar appendages of Pteronia incana(Burm) has shown that there are two types of trichomes. The non-glandular type which consists of two-four cells forms a dense mass of long fibrous hairs, covering the entire surface of plant. The glandular trichome types which are club-oval shape and consist of several glandular cells. The gland cells of the glandular trichome are characterized by a dense cytoplasm containing osmophilic droplets, various organelles such as modified plastids, endoplasmic reticulum, a large nucleus with a dense cytosol. The secreted material accumulates in a cavity beneath a wall derived from separation of the cuticularized outer wall surface of the top tier of secretory cells and are released to the outside when the cavity ruptures. Only the apical pair of cells participates in secretion. Cells of both types possess plastids without thylakoids. These active compounds secreted by P. incana might be the reason why this plant is unpalatable to livestock.   Key words:  Pteronia incana, trichomes, oil glands, electron microscope