Trichomes that secrete substances of a mixed nature in the vegetative and reproductive organs of some species of Moraceae

ABSTRACT

This study aimed to obtain new information about the distribution, morphology and content of secretory trichomes present in the vegetative and reproductive organs of four species of Moraceae: Artocarpus heterophyllus, Dorstenia cayapia, Maclura tinctoria and Sorocea bonplandii. Stem, leaf, flower and inflorescence samples were processed for scanning electron and light microscopy. The species have secretory trichomes on the leaf blade, petiole and stem and also on the inflorescence and flowers of D. cayapia and S. bonplandii and on the peduncle of the inflorescence in A. heterophyllus. These trichomes are of the capitate type in all species, but A. heterophyllus also possess peltate secretory trichomes. Both trichome types exhibit a multicellular head and a unicellular peduncle. Peduncle size and head cell number varies according to species. Peltate trichomes located in depressions were found only in species of Artocarpus, and so should be of diagnostic value for the genus. In all species the trichomes secrete polysaccharides, alkaloids and lipids; phenolic compounds occur in A. heterophyllus and M. tinctoria trichomes. These trichomes probably act in the protection against herbivores, pathogens, desiccation and/ or UV radiation. Moreover, the trichomes found in the inflorescence of D. cayapia may exert a function in pollen grain adhesion.

Keywords:
anatomy; Artocarpus; Dorstenia; flower; gland; leaf; Maclura; morphology; Sorocea