Rhizosphere Ion Composition Shapes Microbial Communities and Is Associated with Plant Growth Variation in...

Soil salinization severely constrains plant growth, yet the roles of ion composition and rhizosphere microbial communities in shaping plant performance remain poorly resolved. Here, we investigated multiple crop and wild plant species in saline-alkali soils and compared rhizosphere ion composition, microbial communities, and plant growth status. Restricted plant growth was consistently associated with elevated Na⁺ and Cl^- concentrations, while fungal diversity was significantly higher in well-growing plants. Ion composition (particularly Na⁺, Cl^-, SO₄^2-, and Mg²⁺) was strongly correlated with microbial community structure, and a set of microbial taxa, including bacterial phyla such as Deinococcota and Gemmatimonadota and fungal phyla within Ascomycota and Basidiomycota, were repeatedly associated with plant growth status across species. Notably, plant species exhibited distinct apparent, threshold-like responses, and in several cases, plant growth differences were not fully explained by salinity levels alone, suggesting that rhizosphere microbial communities may buffer salt stress. Together, our results reveal that ion composition governs plant growth not only through direct ionic stress but also via microbially mediated pathways, highlighting an ion-microbe-plant interaction framework underlying growth variation in saline-alkali soils.