Morphology and ontogeny of tannin-producing structures in two tropical legume trees

Abstract

Two legume trees largely known as tannin producers — Dimorphandra mollis Benth. (Caesalpinioideae) and Stryphnodendron adstringens (Mart.) Coville (Mimosoideae) — were used as models to elucidate the morphology and ontogeny of tannin cells. Vegetative parts of plants were processed for observation using light and electron microscopy (scanning and transmission). Idioblasts, found even in young plants of both species, and secretory trichomes, observed in vegetative buds of mature plants of S. adstringens, are responsible for tannin production. The tanniniferous idioblasts originate from protoderm and also from ground meristem cells. The ground meristem proved to be the best place to study the development of tanniniferous idioblasts at different stages of development, which allowed us to monitor the production and accumulation of tannins in the same tissue. Our data indicate that there is a relationship between the production of tannins and the process of vacuolation of tanniniferous cells. The results also indicate the probable performance of rough endoplasmic reticulum (RER) and plastids in the production of tannins.