Peroxidase mediated hydrogen peroxide production in barley roots grown under stress conditions

Abstract

All applied metals (Co, Al, Cu, Cd) and NaCl inhibited barley root growth. No root growth inhibition was caused by drought exposure, in contrast to cold treatment. 0.01 mM H2O2 stimulated root growth and GA application did not affect root growth at all. Other activators and inhibitors of H2O2 production (SHAM, DTT, 10 mM H2O2, 2,4-D) inhibited root growth. Loss of cell viability was most significant after Al treatment, followed by Cd and Cu, but no cell death was induced by Co. Drought led to slight increase in Evans blue uptake, whereas neither NaCl nor cold influenced this parameter. DTT treatment caused slight increase in Evans blue uptake and significant increases were detected after 2,4-D and 10 mM H2O2 treatment, but were not induced by others stressors. Metal exposure increased guaiacol-POD activity, which was correlated with oxidation of NADH and production of H2O2. Exposure to drought caused a minor change in NADH oxidation, but neither H2O2 production nor guaiacol-POD activity was increased. Cold and NaCl application decreased all monitored activities. Increase in NADH oxidation and guaiacol-POD activity was caused by 10 mM H2O2 and 0.01 mM 2,4-D treatment, which also caused enhancement of H2O2 production. Slight inhibition of all activities was caused by 0.01 mM H2O2, GA, DTT; more pronounced inhibition was detected after SHAM treatment. The role of H2O2 production mediated by POD activity in relation to root growth and cell viability under exposure to some abiotic stress factors is discussed.