Role of nitric oxide in improving seed germination and alleviation of copper-induced photosynthetic inhibition in Indian mustard

Heavy metal stress limits crop production through its effects on seed germination and photosynthesis. Nitric oxide (NO), a versatile signaling molecule, plays a significant role in heavy metal stress tolerance. In the present investigation, the efficacy of NO application in the alleviation of copper (Cu) induced adverse impact on seed germination and photosynthesis of mustard plant (Brassica juncea L.) was evaluated. Pretreatment with NO donor sodium nitroprusside (SNP), significantly improved seed germination and alleviated Cu-accrued oxidative stress in B. juncea seeds. However, in the absence of NO, Cu showed a higher reduction in seed germination rate. Further, NO modulated the activities of antioxidant enzymes and sustained the lower level of lipid peroxidation by reducing H2O2, and thiobarbituric acid reactive substances (TBARS), thereby elevated the antioxidative capacity in Cu-exposed seeds. Seeds pretreated with NO also retained higher amylase activities for the proper seed germination when compared with control. NO mitigated Cu toxicity through an improved antioxidant system, and reducing Cu-induced accumulation of reactive oxygen species (ROS), reduction in lipid peroxidation improving photosynthetic efficiency and growth of the mustard plant. It may concluded that NO improved amylase activity, modulated activity of antioxidant enzymes, and enhanced the germination rate seeds under Cu stress, thereby improved photosynthesis and growth.