Anatomia e histoquímica das estruturas secretoras da folha de Casearia decandra Jacq. (Salicaceae)

摘要

Extensive investigations have emphasized the therapeutic properties of Casearia species related with compounds secreted by specialized structures in the leaves. Therefore, the objective of this study was to characterize anatomical and histochemically the secretory structures present in leaves of C. decandra. Material was collected from natural populations of Mata da Biologia (Zona da Mata of Minas Gerais State, municipality of Vi?osa). Leaves were fixed in FAA and subjected to usual methodology to obtain permanent slides. The sections were stained with toluidine blue pH 4 for structural characterization, with xylidine ponceau for total protein and PAS for neutral polysaccharides. The other histochemical tests were applied to transversally and longitudinally sectioned fresh samples. The secretory system of C. decandra consists of ducts and cavities dispersed on the leaf lamina and petiole and idioblasts present in the vascular tissues, cortical parenchyma of the midrib and in the palisade parenchyma. The ducts are distributed in the cortical parenchyma of the rib and continue in this same region of the petiole. In the mesophyll there are numerous cavities in the subepidermic layer or distributed in the interface between the palisade and spongy parenchyma. Lipophilic and hydrophilic substances were detected, confirming oil-resin lipids within ducts and cavities, and phenolic compounds, of the tannin type, within idioblasts and parenchyma. Alkaloids, polysaccharides and proteins were not detected as secretory products. This work reported the presence of ducts and cavities for the genus Casearia. Histochemical tests confirm the secretory product complexity, besides indicating fundamental tissues such as sites of synthesis and/or accumulation of phenolic compounds.