Main mechanisms and classification of exogenous substances alleviating plant salt stress

One of the environmental factors limiting agricultural production and vegetation construction is salt stress. A large number of studies have identified the potential of exogenous substances in alleviating plant salt stress. Here, we reviewed 122 articles related to the mechanism of plant salt tolerance and the role of exogenous substances. We found that 50 types of exogenous substances are used to alleviate salt stress in plants, and they are divided into 7 categories: regulating ion balance and pH, inducing and synthesizing osmotic adjustment substances, inducing antioxidant enzymes, hormone regulation, inducing gene expression and signal transduction, and improving photochemical system and microbial regulation mechanism.We summarized the progress in each mechanism and proposed some new research frontiers in this regard.