Effects of water deficit stress on membrane properties, lipid peroxidation and hydrogen peroxide metabolism in the leaves of barley genotypes

Two barley genotypes, cultivar Aramir and line R567, were subjected to water stress for 24 hours by immersing their roots in polyethylene glycol (PEG 6000) solution of osmotic potential -1.0 MPa. The relative water content (RWC) in the leaves of both genotypes lowered under the stress conditions. Reduction of RWC led to membrane disorganization, which is evidenced by the injury index data. The injury index was lower in the leaves of cv. Aramir as compared with line R567. The level of lipid peroxidation decreased under stress conditions in the leaves of both genotypes. Hydrogen peroxide content also decreased in the leaves of stressed plants relative to the control ones. The decrease was higher in Line R567 and was accompanied by a decrease in ascorbic acid level in the leaves of that genotype. In the leaves of cv. Aramir water stress did not affect the ascorbic acid content. The examined genotypes showed little or no changes in the activity of ascorbic acid peroxidase in the response to water stress. No evidence of an increase in the level of oxidative stress during water depletion in studied genotypes was seen. Water stress-induced decrease in the level of hydrogen peroxide without an increase in the activity of ascorbic acid peroxidase indicate that other mechanisms may be involved in the detoxification of hydrogen peroxide.