Abstract
Drought stress is one of the main causes for crop yield reduction in the majority of agricultural regions of the world. The effects of sodium nitroprusside (SNP; nitric oxide donor) treatment on induced drought stress were investigated. Drought stress induced by polyethylene glycol (PEG) with different concentrations 5%, 10%, 15% and 20% and previous four concentrations of both poly ethylene glycol and 100 mu M of SNP on rice (Oryza sativa) culture were used. The results showed that, while drought conditions increased after four weeks of administration, the stress signals increased markedly via H2O2 and MDA as a response to elevated oxidative damage promoted by lipid peroxidation under elevated free radical formation. The decrease in water potential also increased the contents of AsA and GSH as a strongly antioxidant defense compound against induced oxidative damage, total soluble sugars, total amino acids, total phenols and PAL activity. All PEG and nitric oxide treatments significantly increased the total soluble phenols contents and PAL activity induced under oxidative stress condition and SNP signaling action controlled the oxidative damage. In addition, the increase in the activity of various antioxidant defense enzymes SOD, APX, GR and CAT represent the protective activity to counteract the oxidative injury promoted by drought conditions.