Glutathione and salicylic acid combined application mitigates salt-induced damage during early seedling growth of rice through stomatal, oxidative, and carbonyl regulation

Abstract

Salt stress threatens global rice production by disrupting critical physiological processes, including stomatal dysfunction, thermal dysregulation, and excessive accumulation of reactive oxygen species (ROS) and reactive carbonyl species (RCS), culminating in severe oxidative damage. While glutathione (GSH) and salicylic acid (SA) are individually known to enhance salt tolerance, the potential effects of their combined application (GSH + SA) remain largely unexplored, particularly in relation to RCS-mediated salt damage in rice. Here, we investigated the protective efficacy of combined GSH (2 mM) and SA (1 mM) treatment against salt stress (150 mM NaCl) in rice seedlings, targeting growth, photosynthetic capacity, stomatal function, thermal regulation, and oxidative damage. Salt stress severely compromised plant performance, reducing root/shoot length and biomass while drastically increasing leaf temperature by 14.9%. Total chlorophyll and carotenoid contents decreased by 43.5% and 37.0%, respectively. In contrast, GSH + SA co-treatment alleviated these adverse effects, enhancing total chlorophyll and carotenoids by 20.4% and 21.1%, respectively, and lowering leaf temperature by 3.6%. The combined treatment also enhanced stomatal dimensions, increasing stomatal length and width by 8.4% and 22.7%, respectively. Furthermore, GSH + SA markedly reduced oxidative damage by lowering H₂O₂ and TBARS accumulation by 29.4% and 28.8%, respectively, and suppressing protein carbonylation by 30.9%. These findings indicate that the combined application of GSH and SA influences multiple salt stress-related pathways and may represent a promising approach for improving salt stress tolerance during early growth stages of rice under salt-affected agricultural conditions.