Nitric oxide and arginine mitigate salt stress through physio-biochemical modulations and ions regulation in Brassica napus L.

Salinity stress is a devastating environmental issue among abiotic stresses. It has severely affected global crop production. It has become crucial for scientists to unearth new strategies for mitigating salinity stress. In this study, a completely randomized experimental design was formulated. Two cultivars (Super and Sandal) of Brassica napus L. were utilized in this work. The treatments applied in this study included NaCl (100 mM), nitric oxide (NO; 150 µM) and arginine (Arg; 0.5 mM). The results revealed that, compared with those of the control plants, the growth, chlorophyll content, relative water content, total soluble protein, K⁺ and Ca²⁺ contents of the shoots and roots, and yield parameters were lower under salt stress. The membrane permeability, malondialdehyde, H₂O₂, total phenolics, free proline, catalase, peroxidase and ascorbate peroxidase activities, and sodic level were increased under salinity. In contrast, foliar sprays of NO and Arg and their combined application significantly increased the plant growth, chlorophyll content, RWC, total soluble protein, K⁺ and Ca²⁺ contents and yield parameters of canola in stressed and control plants. These supplements reduced the membrane permeability and MDA, H₂O_2, Na⁺ and Cl^- contents but increased the total phenolics, free proline, and antioxidant enzymes activities in stressed plants. The findings of this study demonstrated that NO and Arg have potential roles in mitigating the toxic effects of salinity and can increase plant growth and yield.