Propagação, anatomia e cultivo em malhas coloridas de stachytarpheta sellowiana Schauer: uma planta medicinal ameaçada de extinção

Abstract

Stachytarpheta sellowiana Schauer is a native and endemic plant from Brazil, belonging to the Verbenaceae family, occurring mainly in the phytogeographic domain of the Cerrado in areas of Campo Rupestre and is at threat of extinction. As it is a wild plant, this species lacks studies for its domestication, such as propagation, anatomy, and physiology. The present study aimed to: evaluate different S. sellowiana's propagation methods, analyze the morphoanatomical characteristics of S. sellowiana leaves from two natural environments, and evaluate the effect of colored meshes on vegetative growth and secondary metabolites production of the species. In the first experiment, three propagation methods were evaluated: sexual with different seed lots, asexual by cutting, and in vitro establishment. For the germination tests, were used seeds lots collected in the natural habitat, seeds from plants grown in a greenhouse, and seeds from plants grown in full sunbeds. From these seeds, experiments were carried out using different types of substrates for germination (soil/sand mixture in the proportion 2:1 and paper), 5 LED light intensities (26; 70; 100; 113; 144 μmol m-2 s-1) and 7 light spectrums (red; blue; green; white; 70% red: 30% blue; 50% red: 50% blue; 30% red: 70% blue). For asexual propagation, nodal and apical cuttings measuring approximately 10 cm were used, which were transferred to trays containing four different types of substrates (natural environment, soil\sand 2:1, soil, sand) for 90 days. Apical explants of mother plants grown in a greenhouse were used for in vitro establishment, in four different types of culture medium (MS, MS:2, B5, and WPM). For in vitro cultivation, propagation in an acidified medium is indicated because at pH 5.8 there is the development of bacteria. The most suitable form of propagation for the species was via cutting of nodal segments established in the soil substrate of the red latosol type. Propagation by seeds can be employed. However, it is highly influenced by the substrate and the light intensities and quality. In the second experiment, leaves were collected in two natural environments of Serra do Campestre (Cerrado, considered by some to be savannah, and Campo Rupestre of montane grassy-shrubby vegetation). From the morphoanatomical observations, the leaves were classified as pilose, where they occur throughout the epidermis, more frequently on the adaxial surface. No tector trichomes were observed in Cerrado plants. For the photoselective mesh experiment, the treatments consisted of S. sellowiana plants grown under meshes with 50% shading (black, red, and blue) and under the full sun (control). After 300 days, we concluded that the photoselective meshes exert changes in growth, anatomy, production of metabolites, and antioxidant capacity of S. sellowiana plants grown in pots. The species can be grown under full sun to obtain greater dry matter. However, for greater production of antioxidant and iridoid compounds, cultivation under blue meshes is indicated.