The role of root‐associated microbes in growth stimulation of plants under saline conditions

Soil salinization has adverse effects on plant growth due to direct ion toxicity or secondary damage, such as mineral nutrition imbalance and the water stress caused by low osmotic potential. The rhizosphere processes of plants are likely to play an important role in the biological improvement of saline soil. However, the understanding of this remains limited. This review summarizes the progress made recently in exploring the effects of root‐associated microbes especially from halophytic species on the growth stimulation of plants under salinity. For example, halophytes attract and absorb beneficial rhizosphere growth‐promoting bacteria by producing rhizosphere exudates such as organic acids and enzymes, which is conducive to plant growth under salt stress. The plant growth‐promoting exogenous rhizobacteria (PGPR), attached to the roots of halophytes, can promote the growth of plants mainly through the improved absorption of nutrients by the host plants or through producing plant growth regulators. In addition, the colonization of endophytes can regulate plant ion balance and produce secondary metabolites such as growth‐promoting hormone and extracellular enzymes, activating antioxidant systems, and inducing plant system resistance against pathogenic microorganisms, thus promoting the growth of plants under salt stress. The inoculation of arbuscular mycorrhizal fungi (AMF) under salt stress can facilitate plants to change the ion balance or obtain water from the soil, and that the formation of other hyphae may promote the transfer of water and nutrients to plants. Therefore, understanding the effects of root‐associated microbes on the growth stimulation of plants under salinity is of great significance to improving their salt tolerance, so as to improve saline‐alkali land for the construction of a more effective biological improvement model.