ALLEVIATION OF ADVERSE EFFECTS OF SALINITY STRESS ON WHEAT (Triticum aestivum L.) BY EXOGENOUS APPLICATION OF HYDROGEN PEROXIDE

Hydrogen peroxide (H2O2), an active oxygen species, is widely generated in many biological systems and mediates various physiological and biochemical processes in plants. A pot experiment was conducted in the wire-house of the National Research Centre, Giza, Egypt. The experiment consisted of three concentrations of H2O2 (0, 50 and 100 µM) and two concentrations of diluted seawater (3.13 and 6.25 dSm-1), whereas control plants were irrigated with tap water (0.23 dSm-1). Diluted seawater (S1 & S2) caused in general significant decreases in growth parameters, photosynthetic pigments and indole acetic acid (IAA) contents compared to plants irrigated with tap water (S0). Presowing of wheat grains in 50 µM H2O2 (H1) and 100 µM H2O2 (H2) mitigated these harmful effects of salinity on wheat growth parameters, photosynthetic pigments and IAA contents. In contrast, Both salinity levels (S1 and S2) and treatments of H2O2 caused significant increases in total soluble carbohydrate, free amino acid and proline concentrations, as well as some antioxidant enzymes as polyphenol oxidase (PPO), superoxide dismutase (SOD), catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APX) activities, relative to their corresponding control plants. Phenolics, MAD and H2O2 contents increased significantly due to seawater salinity stress levels meanwhile, H2O2 treatment with different concentrations (H1 or H2) decreased significantly phenolics, H2O2 and MDA contents compared with their corresponding controls. We conclude that treatment of wheat grains with H2O2 mitigated the adverse effects of seawater salinity through enhancing the levels of photosynthetic pigments, IAA, antioxidant enzyme activities, osmoprotectant concentrations, all of which were reflected in an improvement in plant performance.