Secretory Hairs of Inula viscosa (L.) Ait.-Development, Ultrastructure, and Secretion

Abstract

The leaves and young stems of I. viscosa (L.) Ait. [a medicinal plant] bear sessile and stalked secretory hairs which secrete throughout the life span of the leaf from its very early stages of development to maturity. Both types of hairs possess a secretory head consisting of 3 types of cells: 1 pair of summit cells, 1 pair of cells below the summit cells and 3 pairs of photosynthesizing cells. All head cells secrete lipids, polysaccharides and protein. In the head cells, smooth and rough endoplasmic reticulum, plastids, mitochondria and Golgi bodies may be involved in secretion. The various cell pairs of the head differ in their sequence of ultrastructural changes throughout the period of secretory activity, in the type of plastid and its involvement in the secretory process and in the manner of the substances secreted to the outside. At various stages of secretory activity, different cell constituents were present in abundance.