Wu, W., Weber, H. Chr. & Imhof, S. (2004):

Morphogenesis and structure of hairs of Tetrapanax papyriferus (Hook.) Koch (Araliaceae)

Beitr. Biol. Pflanzen 73: 213 - 221

Abstract:

The green parts of Tetrapanax papyriferus (Hook.) Koch (Araliaceae) are covered by complex, morning star like, multicellular trichomes. These trichomes initially appear as papilla-like cells of the epidermis, which develop into multicellular, sometimes biseriate stalks. At maturity the stalks are crowned by a star-like structure, consisting of many cells with ray-like protrusions in a globose arrangement, the protrusions radiating into all directions. Altready in early stages of the hairs, these heads are present as morula-like cell agglomerations. The central part of the gead eventually appears brownish, caused by secretory activity.
The hair cover is most prominent on both sides of young leaves, the abaxial sides of older leaves and bracts, on peduncle, pedicels, the upper third of the abaxial side of petals as well as the hypanthium of the inferior ovary. The hair cover on the adaxial surfaces of the older leaves, bracts and petals as well as the upper part of the ovary around the styles is less dense to absent. At the upper part of the ovary the hairs are additionally characterized by having shorter stalks but more rays.
The irritant indumentum, covering the susceptible young and reproductive organs, particularly the lower sides of the leaf organs protecting the buds, is discussed as an adaptation primarily against herbivores. Keywords: Tetrapanax papyriferus- Araliaceae - multicellular hairs - structure - morphogenesis