Melatonin-functionalized silver nanoparticles enhance salinity tolerance in Brassica juncea by modulating antioxidant defence and growth physiology

Soil salinity is a major abiotic stress that severely limits plant growth and productivity by inducing osmotic stress, oxidative damage, and ionic imbalances. The present study evaluated the potential of melatonin-mediated silver nanoparticles (Mel AgNPs) to enhance salinity stress tolerance in Brassica juncea . Pot experiments were conducted using 21-day-old plants exposed to salinity stress and treated with Mel AgNPs at different concentrations (50 and 100 mg L⁻¹) through both root application and foliar spray. Morphological, physiological, and biochemical responses were assessed 48 h after nanoparticle exposure. Salinity stress markedly increased lipid peroxidation and hydrogen peroxide accumulation while suppressing antioxidant defence. In contrast, Mel AgNPs treatment significantly reduced malondialdehyde and H 2 O 2 levels and enhanced the activities of key antioxidant enzymes, indicating effective mitigation of oxidative stress. Improved morpho-physiological performance further confirmed the protective role of Mel AgNPs under saline conditions. Overall, the findings demonstrate that Mel AgNP can effectively enhance salinity tolerance in B. juncea by strengthening antioxidant defence mechanisms and reducing stress-induced cellular damage, highlighting their potential as a sustainable strategy for improving crop resilience under saline environments.