Selenium Pretreatment Regulates the Antioxidant Defense System and Reduces Oxidative Stress on Drought-Stressed Wheat ( Triticum aestivum L.) Plants

摘要

Drought stress is a worldwide problem that constraint plant productivity. The aim of this study was to assess the alleviative effect of two levels of selenium (Se), 5 and 10 mg L^-1, on drought oxidative stress of wheat cv. Giza 168 through monitoring the changes of the plant?s antioxidant system and certain metabolites indicative for oxidative stress . Drought stress increased the accumulation of H₂O₂ and the lipid peroxidation product MDA whereas decreased the activities of the antioxidant enzymes CAT and SOD and the content of Ascorbic Acid (AsA). The activity of guaiacol peroxidase (POD) as well as the contents of proline and the non-enzymatic antioxidants, reduced glutathione (GSH) and alpha tocopherol (α-TQ) were increased in response to drought. In drought-stressed, Se-pretreated plants, H₂O₂ and MDA contents were decreased whereas the activities of the antioxidant enzymes CAT and SOD and the content of the non-enzymatic antioxidants AsA and GSH were increased resulting in elevated membrane stability index and root viability. On the other hand, the activity of POD as well as the contents of proline and the non-enzymatic antioxidant α-TQ were decreased in drought-stressed, Se-pretreated plants which may reflect the attenuation of oxidative stress due to Se pretreatment. The lower dose of Se was, generally, more favorable in this respect. Results indicate that Se pretreatment enhanced tolerance of wheat plants against drought oxidative stress through modulation of the plant?s antioxidant system.