Protective effect of exogenous nitric oxide on alleviation of oxidative damage induced by high salinity in rice (Oryza sativa L.) seedlings

To find the protective role of exogenous nitric oxide (NO) on salinity-stressed rice seedlings, a CRD-based factorial experiment with three replications was conducted in Agronomy Laboratory of the Faculty of Agricultural Sciences, University of Guilan, in 2012. The experimental design consisted of healthy and vigorous seedlings of two rice cultivars, Khazar and Goohar, the last already known as promising SA13 line, which were exposed to 0 (Control), 50 mM NaCl, 50 μM sodium nitroprusside (SNP) as NO donor solution supplemented with simultaneous 50 mM NaCl + 50 μM SNP for four days. After 4 days, electrolyte leakage and malondialdehyde (MDA) content, activities of antioxidant enzyme, destruction of chlorophyll and soluble protein content in leaves were measured in treated and control plants. The results showed that simultaneous treatment of rice leaves with SNP, suppressed the ion leakage content by 8.5% compared with the results of NaCl treatment. Furthermore, SNP increased the activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and catalase (CAT). Exogenous application of NO also reduced peroxidation of membrane lipids, whereas increased the soluble protein content and chlorophyll pigments in rice leaves under salinity stress. These results suggested that NO could effectively protect rice seedlings from salt stress damaged by enhancing activities of antioxidant enzymes to quench the excessive reactive oxygen species caused by salt stress.