Abstract

Salt stress is one of the major environmental constraints in agriculture, significantly limiting crop yield and causing substantial economic loss worldwide. Silicon (Si) and selenium (Se) are widely recognized as beneficial elements for plants, and the application of Si- and Se-based fertilizers is considered a promising strategy for promoting crop growth and sustainable agricultural production under expanding salinization of arable land. In this study, aiming for the targeted application of Si and Se in agricultural production, the individual and synergistic effects of Si and Se on salt stress resistance in tomato when applied via root application or foliar spray were comprehensively investigated. Plant growth parameters, photosynthesis performance, oxidative damage, the activity of the antioxidant system, sodium/potassium (Na/K) content, and the expression of genes related to Na/K homeostasis were determined and further compared using principal component analysis (PCA). The results showed that salt stress markedly inhibited plant growth and photosynthetic performance, while inducing oxidative damage and disrupting Na/K homeostasis in tomato seedlings. In contrast, the application of both Si and Se significantly promoted tomato growth and ameliorated the detrimental effects of salt stress. Moreover, Si and Se exhibited a synergistic effect in promoting salt stress resistance under both root and foliar application. Root application of Si and Se is more effective in enhancing ionic homeostasis, while foliar spray of Si and Se is more effective in promoting photosynthesis performance under salt stress. Overall, considering the convenience and use-cost efficiency of Si and Se application in agricultural practices, the results of this study showed that the synergy application of Si and Se via foliar spray is most effective in promoting salt stress resistance in tomato through modulating photosynthesis performance, antioxidant capacity, and ionic homeostasis.