Effect of nitric oxide (NO) on the induction of callus and antioxidant capacity of Hyoscyamus niger under in vitro salt stress

Generation of reactive oxygen species (ROS) under salt stress can cause oxidative damage. Nitric oxide (NO) is considered as a functional molecule in alleviating the oxidative damage of salinity to plants through modulating antioxidant metabolism. In the present study, effects of sodium nitroprusside (SNP), a NO donor, on induction of callus and seed germination, and antioxidant capacity of Hyoscyamus niger seedlings were studied under 0, 50, 100 and 150 mM NaCl stress. NO stimulated the germination of NaCl-treated seeds. NaCl treatment significantly induced accumulation of H2O2 and thiobarbituric acid-reactive substances (TBARS) in Hyoscyamus niger, and application of 100 μM SNP stimulated ROS-scavenging enzymes and increased scavenging activity (DPPH), hydroxyl radical (OH•) scavenging activity and chelating activity of ferrous ions, resulting in lower lipid peroxidation induced by NaCl stress. Therefore, it can be concluded that the increased antioxidant capacity by NO might be responsible for its function in alleviating the inhibition of Hyoscyamus niger growth and cell damage by salt stress. Also the effect of SNP on the induction of callus of Hyoscyamus niger was investigated. Callus fresh weight increased significantly in the combined effect of 50 μM SNP with other plant growth regulators (PGR) compared to control. It is evident that SNP has a direct effect on the induction of callus by interacting with cytokinins and auxins.