Special attention is given to Spondias dulcis Forst. F. for its ability to secrete a gum with medicinal properties. In other species of Anacardiaceae, most of the studies report the ultrastructure and development of the ducts, being scarce data about the chemical composition of secretory products. The aim of this work is to study the anatomy of the secretory system of S. dulcis and characterize by histochemistry the secretion produced. Stems of plants with 45 days old were study by conventional plant anatomy methods. The main classes of secretion chemical compounds were characterized in situ by histochemical tests. The secretory system of S. dulcis consists in very elongate ducts and idioblasts. The ducts are associated to the phloem and in the pith, and the idioblasts occur near the phloem and in the cortex. Ducts are formed by a secretory epithelium of cuneiform to flattened cells, with thin walls, dense cytoplasm and large nuclei with prominent nucleoli. The ducts associated with phloem have, in addition to epithelium, two to three layers of flattened parenchyma cells arranged in a circle forming a sheath. The histochemical tests reveal the presence of tannins in the cortical idioblasts. The secretion of the ducts is mainly constituted by essential oils, polysaccharides and phenolic compounds (probably flavonoid aglycones), which led us to say that is a gum-resin.
Anacardiaceae; Spondias dulcis; stem anatomy; secretory ducts; secretory idioblasts; histochemistry
