Respostas bioquímicas e fisiológicas de híbrido de milho submetido ao déficit hídrico com aplicação foliar de quitosana e seus derivados

Abstract

Under greenhouse conditions, hybrid BRS 1030 was submitted to water deficit. In this study, we hypothesized that the application of chitosan and its derivatives in the leaves would be able to minimize the effects of water deficit imposition, associating an effective antioxidant protection through enzymatic and non-enzymatic defense mechanisms. Some studies have already shown that chitosan induces a certain tolerance and protection of plants. The same, in other studies conferred a higher activity of antioxidant enzymes, phenolic compounds and proline. Chitosan has a chemical structure of nucleophile, which makes it possible for structural modifications. Such modifications may confer a faster recognition of their sites in the plant cell, providing a cascade of chemical reactions that confer the activation of plant defense mechanisms against water deficit. Chitosan and its derivatives (N-succinoylic (SUC) and N, O-dicarboximethyl (MCA)) were applied to the BRS 1030 hybrid by foliar spraying at the pre-flowering stage. After the application the plants were induced to the water deficit for 15 days. The gas exchange analyzes were performed on the first and fifteenth day of water deficit, using a portable photosynthesis system (IRGA, Model LI-6400 XT, Li-Cor, Lincoln, Nebraska, USA). For this parameter the photosynthetic rate and the stomatal conductance of the plants were evaluated. For the biochemical analyzes the leaves of the spike were collected on the first and fifteenth day of water deficit. The application of the chitosan and chitosan derivatives potentiated the activities of antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and guaicol peroxidase; and of osmoprotective molecules like proline, total soluble sugars, total amino acids and starch. The application of the molecules conferred a greater photosynthetic activity and stomatal conductance evidencing a greater induction of this plant the tolerance to the water deficit.