Anatomy of vegetative organs of Scutellaria agrestis, a medicinal plant cultivated by riverine populations of the Brazilian Amazon

Scutellaria agrestis A. St.-Hil. ex Benth., Lamiaceae (trevo-roxo) is cultivated for medicinal purposes by residents of the riverine communities in the State of Amazonas, Brazil. This study aimed to characterize the anatomy and to make histochemical analysis on vegetative organs of S. agrestis. Samples of the leaf, stem and root were collected from five plants cultivated by the communities located in the Solimões river, Amazon. These samples were fixed and prepared following standard techniques for scanning electron microscopy and for light microscopy. Histochemical tests were carried out on sections to detect the main classes of compounds present in the secretion. Numerous glandular trichomes are seen in both leaf and stem of S. agrestis. The leaves are amphihypostomatics and show dorsiventral mesophyll. Hydathodes are present at the tip of the marginal teeth. Anthocyanin pigments occur into the epidermal cells of the stem, petiole, and abaxial leaf surface. The petiole is concave-convex shaped and bears collateral vascular bundles. The stem showed square-shaped, evident endoderm, collateral vascular bundles and parenchymatous pith. The root displays a typical protostelic structure. Idioblasts containing mucilage and phenolic compounds occur in the cortex. These data are important, as they can be useful to identify this species, contributing to the quality control of the medicinal plant. Keywords: glandular trichomes, histochemistry, hydathodes, medicinal plant, mucilage idioblast, trevo-roxo