MgO nanoparticles alleviate salinity-induced physiological and biochemical disruptions in soybean.

Salinity stress severely limits soybean (Glycine max L.) productivity by disrupting physiological and biochemical processes. This study investigated the potential of magnesium oxide nanoparticles (MgO-NPs) to mitigate salt-induced damage. Soybean plants were grown under two salinity levels-non-saline (0 mM NaCl) and saline (75 mM NaCl)- in a controlled pot experiment. At the trifoliate stage, leaves were sprayed with MgO-NPs at 0, 100, 200, 400, and 600 ppm. Salinity markedly reduced relative water content (RWC) (to 69%), photosynthetic rate (to 20 µmol CO₂ m-2 s-1), and membrane stability index (MSI) (to 56%), while increasing oxidative stress markers. Foliar application of 400 ppm MgO-NPs significantly alleviated these effects, increasing RWC to 87%, photosynthesis to 35 µmol CO₂ m-2 s-1, and MSI to 78%. Treated plants showed higher chlorophyll and carotenoid contents, along with elevated proline and soluble sugars and reduced malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) levels. Antioxidant activity improved modestly under both saline and non-saline conditions. Importantly, 400 ppm MgO-NPs enhanced yield traits under salinity, increasing pod number, 100-seed weight, and seed yield per plant by about 30%-38%. These results indicate that MgO-NPs, particularly at 400 ppm, effectively mitigate salinity stress by modulating physiological and biochemical mechanisms, with strong potential for improving soybean performance under saline environments. Field studies are suggested to validate practical application.