Função dos tricomas vesiculares na tolerância à salinidade em Atriplex nummularia

Abstract

Epidermal bladders play a fundamental role in the exclusion of toxic ions in some halophyte species. To better understand the role of these structures in the tolerance to salinity, an experiment was carried out with plants of A. nummularia irrigated with waters of three levels of osmotic potential (-0.1; -1.4; -2.7MPa), formulated from NaCl (0; 300 and 600mmol L-1), having plants with Epidermal bladders and plants partially absent from these bladders cells. A randomized block design in a 3 x 2 factorial scheme with five replications was adopted, totaling 30 experimental units. Physiological evaluations were performed (hydric Potential - Ѱw, Osmotic Potential - Ѱo and Pressure - Ѱp, Relative Water Content, Osmotic Adjustment, Pressure-Volume Curve - PV, Liquid photosynthesis, Stomatal conductance, Sweating and Water use efficiency), Extravasation electrolyte, lipid peroxidation and enzyme activity (superoxide dismutase, ascorbate peroxidase, catalase). The experiment was carried out in a protected environment over a period of 30 days. The evaluated results allowed to identify the strong contribution of epidermal bladders in physiological and biochemical relationships. The Ѱo values obtained on the osmometer confirmed that the leakage of inorganic solutes from the bladders cells through maceration are responsible for the most negative osmotic potentials. The parameters obtained with the PV curve allowed to confirm that brushing performed to remove the bladders cells managed to exclude solutes concentrated in the apoplastic space and corrected the discrepancy that occurred between the values accessed by PV curve and by osmometry. Influence of vesicular trichomes on photosynthetic and antioxidant metabolism in Atriplex nummularia plants subjected to salt stress. Chlorophyll fluorescence data demonstrated the integrity of the photosystem component (FSII) even with the removal of bladders cells and elevated salinity. The evaluation of electrolyte leakage, together with the increase in the content of MDA suggest that the partial removal of the vesicles presents a higher probability of oxidative stress. Among the enzyme activities evaluated, APX activity is one of the main mechanisms adopted by Atriplex nummularia in the detoxification of H2O2.