Aspectos morfo-anatômicos e histoquímicos de lantana fucata l. (Verbenaceae)

Abstract

The use of medicinal plants by people around the world has been very significant lately. The morpho-anatomical characterization of medicinal plants is important in the quality control for phytotherapics in order to guarantee the safety and efficacy of these products. Among the botanical families with medicinal characteristics or potential medicinal characteristics, Verbenaceae stands out, a family with species widely used by popular medicine and which presents a wide range of studies on chemical composition. Lantana fucata, popularly known as cambará-roxo, is frequently cited in ethnobotanical studies conducted in Rio Grande do Sul. Its indicated use is as a healing agent for joint pain and rheumatism, but there is no scientific proof of its efficacy. The objective of this work is to characterize the morpho-anatomical and histochemical composition of stems and leaves of Lantana fucata. Different populations were collected and later, the testimony material was included in UFFS’s herbarium. Part of the plant samples were fixed and processed following usual protocols for studies in photonic microscopy. The observations and recording of images were performed under optical microscope and stereomicroscope. Specific reagents were used for the histochemical tests. Lantana fucata features a simple petiolate leaf, opposite phyllotaxis, kladrodomus venation, as well as pubescent quadrangular branches. In its leaf blades there are two types of glandular trichomes and a type of tectoric trichome, uniseriate epidermis, striated cuticle, and an anomocytic stomatal complex. In addition, its leaves are hypoestomatic with dorsiventral mesophyll, 2-3 layers of spongy parenchyma on the abaxial side, 1-2 layers of palisade parenchyma on the adaxial side, and medial vascular bundle in the form of a continuous arch. In the stem, the presence of glandular and non-glandular trichomes was also verified, featuring 2-3 layers of colenchyma in the stem. L. fucata reacted positively to total lipids (glandular trichomes of the peduncle stem, head and cuticle), proteins (glandular trichomes, peduncle and head), mucilages and pectins (most cells and glandular trichomes), and lignin (vessel elements and fibers). The glandular stem trichomes reacted positively to lipids. In addition, glandular leaf trichomes reacted positively to proteins, glycoproteins, mucilages, and pectins. Furthermore, it was found that some glandular trichomes have their own specific kind of yellowish color, whose chemical nature was not possible to identify because of the lack of more specific histochemical reagents. Although there is a need for more detailed studies about the chemical constitution of the secreted substances, this work provides information for the knowledge of anatomical structures that can be used in the quality control of eventual phytotherapics that may be developed with the target plant.