Assimilação e transporte de nitrogênio em Brugmansia suaveolens

Abstract

Several alkaloids with important biological activities have been isolated from species of the Solanaceae family. Brugmansia suaveolens has been cultivated to the purpose of phytotherapeutic medicines production and shows a potential as raw material for the isolation of scopolamine for the pharmaceutical industry. In Rio Grande do Sul State, it is found in natural conditions and grown as ornamental plant. The detailed knowledge of the process of nitrogen assimilation and transport in Brugmansia suaveolens enables the development of strategies for more efficient cultivation of this species, aiming the production of alkaloids, secondary nitrogen metabolites. This study aimed to determine the effect of nutrition on the activities of the nitrate reductase (NR) and glutamine synthetase (GS) enzymes in the roots and leaves, and on the content of important nitrogen molecules in leaves, roots and xylem sap. For that, the source of nitrogen varied among NH4NO3, amino acids (glutamine, phenylalanine, arginine), NO3 - and NH4 +. The amino acid glutamine was the main organic component of the nitrogen fraction carried in the xylem, among the different sources of nitrogen, except NO3 -. Among the inorganic forms, high levels of ammonium were detected in all treatments, while the nitrate predominated in plants under treatments in the presence of that ion. The RN and GS activities were high in the leaves and little significant in the roots, which suggests that the leaves are the preferred sites of nitrogen assimilation in this species. ix