Nitric Oxide Mitigates the Salt-Induced Oxidative Damage in Mustard by UpRegulating the Activity of Various Enzymes

The salt stress limits the production of mustard throughout the world and it is one of the major abiotic stresses. Crop productivity is declining due to the limited area of fertile land. In order to investigate the effects NO donor on salt tolerance and the recovery of Brassica juncea. (L) cv. RGN-48, sodium nitroprusside (SNP) was applied at 1, 10 or 100 µM concentrations as foliar spray for five days consecutively. SNP triggered a significant increase in the main antioxidative enzymes including catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) along with the increase in the enzymes involved in nitrogen metabolism (nitrate reductase), photosynthesis and respiration (carbonic anhydrase, rubisco, fumarase, hexokinase and succinate dehydrogenase). On the other hand, decrease in programmed cell death (PCD) and the contents of hydrogen peroxide (H₂O₂), superoxide anion (O₂^.−) and malondialdehyde (MDA) was observed in NaCl-stressed plants subjected to the different concentrations of SNP. Consequently, the spray of SNP restored several photosynthetic attributes i.e. SPAD chlorophyll, chlorophyll fluorescence and gas exchange parameters in NaCl-stressed plants. These results suggested that exogenous application of SNP is useful in ameliorating the toxicity generated by NaCl in mustard plants.