Effect of sodium nitroprusside on physiological and anatomical features of salt-stressed Raphanus sativus

Sodium nitroprusside (SNP), which produces nitric oxide (NO) has the well-documented potential to alleviate the adverse effects of various abiotic stressors such as salinity. The present study aimed at investigating how the application of SNP can ameliorate the adverse effects of salt stress and boost tolerance in Raphanus sativus. Salt stress induced by application of 100 or 200 mM NaCl significantly decreased photosynthetic pigments and chlorophyll fluorescence, followed by a significant reduction in carbohydrate content. SNP treatment increased salt-tolerance in plants by inhibiting the adverse effect of salinity on the photosynthetic apparatus and the accumulation of sugars. Salt stress was accompanied by a reduction in total antioxidant power (FRAP), accumulation of damaging levels of H2O2, lipid peroxidation, and reduction in protein, while SNP enhanced FRAP, reduced H2O2 and lipid peroxidation, and restored protein abundance. SNP treatment also increased hypocotyl growth of salt-stressed plants, accompanied by improvement in anatomical structure. Cross sections of the hypocotyl showed increased diameter of the central cylinder and thickness of the casparian strip in the SNP-treated plants under stress conditions. Indeed, the observed improvement in the growth of hypocotyl and leaves of saltstressed radish plants treated with SNP, in parallel with improved physiology and anatomical features, suggested that NO can regulate diverse mechanisms to effectively increase salt tolerance.