Helal Ragab Moussa and Mohamed Abd El-Fattah Hassan Mohamed( 2011). Role of nitric acid or H2O2 in antioxidant defense system of Pisum sativum L. Under drought stress Nature and Science, 2011; 9(5)
Abstract: Water shortage is likely to be one of the major global environmental stresses of the 21st century. Drought is an important environmental constraint limiting the productivity of many crops worldwide. Experiments were conducted to investigate the effects of seed pretreatment by hydrogen peroxide at 70 mM or sodium nitroprusside (SNP; nitric oxide donor) at 10 μM on drought tolerance in pea seedlings. Osmotic stress was provoked by addition of polyethylene glycol to the nutrient solution at the flowering stage. H2O2 or SNP are active molecules involved in mediation of various biotic and abiotic stress induced physiological responses in plants. H2O2 or SNP pretreatment alleviate oxidative damage, accelerate proline accumulation and enhance total chlorophyll, carotenoid, photosynthetic activity (14CO2–fixation), and total yield/plant in pea seedlings subjected to osmotic stress. The results showed that osmotic stress induced decrease in the enzyme activities of ascorbate peroxidase, glutathione peroxidase, catalase and overproduction of O2˙¯ in pea leaves, which in turn caused exacerbation of lipid peroxidation and depression of photosynthesis. Application of H2O2 or SNP significantly increased the enzyme activities and decrease O2˙¯ production and hence inhibited lipid peroxidation. Level of H2O2, proline and Evan blue uptake in seedlings pretreated with H2O2 or SNP were markedly lower than under drought stress, indicating the operation of antioxidant system in them. Moreover, seedlings arising from H2O2 or SNP pretreatment enhanced the membrane stability, as revealed from greatly reduced malondialdehyde content. The present data suggest that pea seed pretreatment with H2O2 or SNP, a stress signal, could trigger the activation of antioxidants in seeds, which persists in the seedlings to alleviate the oxidative damage, leading to improvements in physiological attributes for the seedling growth under drought.
Keywords: (Antioxidative enzymes, Drought stress, Photosynthesis, Proline, Pea.)
