Sodium nitroprusside (SNP) alleviates the oxidative stress induced by NaHCO3 and protects chloroplast from damage in cucumber

Abstract

Oxidative damage is often induced by abiotic stress, nitric oxide (NO) is considered as a functional molecule in modulating antioxidant metabolism of plants. In the present study, effects of sodium nitroprusside (SNP), a NO donor, on the phenotype, antioxidant capacity and chloroplast ultrastructure of cucumber leaves were studied under NaHCO₃ stress. 30 mM NaHCO₃ treatment significantly induced accumulation of H₂O₂ and thiobarbituric acid-reactive substances (TBARS) in cucumber leaves, and led to serious electrolyte leakage. Application of 100 μM SNP stimulated reactive oxygen species (ROS)- scavenging enzymes and increased antioxidant capacity, resulting in lower lipid peroxidation and membrane damage induced by NaHCO₃ stress. As a main organelle of ROS formation, chloroplast ultrastructure was seriously damaged by NaHCO₃ stress and SNP treatment obviously reversed the damage. On the contrary, the above effects of SNP were not observed by application of potassium ferrocyanide which is an analog of SNP that does not release NO. Therefore, it could be concluded that the NO from SNP might account for the alleviating effect of NaHCO₃ stress on cucumber plants.

Key words: Cucumber, alkaline stress, nitric oxide, antioxidant, chloroplast ultra structure.