PLS-PM Modeling Reveals Biochar-AMF Synergy on Salinity Tolerance in Suaeda salsa Through Ion Homeostasis and...

Soil salinization imposes severe ionic and osmotic stress on plants, threatening ecosystem sustainability. Biochar (BC) and arbuscular mycorrhizal fungi (AMF) have shown potential to alleviate salinity stress, but their interactive effects on the soil-plant-microbe continuum have not been fully elucidated. This study utilized partial least squares path modeling (PLS-PM) to assess the individual and combined contributions of BC and AMF to sodium (Na⁺) homeostasis in Suaeda salsa. Results indicate that BC primarily acted as a soil conditioner, reducing Na⁺ bioavailability by 49.19% (compared to the unamended saline control) (as indicated by the soil Na⁺/K⁺ ratio) through enhanced adsorption and cation exchange, thereby contributing to improved soil health (including an 87.23% increase in SOC). In contrast, AMF elicited a plant physiological response, characterized by the upregulation of antioxidant enzymes (such as a 114.85% increase in catalase) and osmotic regulators (e.g., a 90.22% increase in soluble sugars), which collectively mitigated oxidative stress and promoted vacuolar sequestration of Na⁺. A strong synergistic effect (E > 0) was observed. The PLS-PM model quantitatively delineated the causal pathways, revealing that BC and AMF function through complementary soil-soil solution-root-leaf-vacuole transport routes. This study reveals the mechanism underlying the interaction between biochar and AMF, while quantifying the pathways through which they synchronously regulate the rhizosphere chemical environment and internal detoxification in plants, providing new insights into how halophytes cope with environmental stress challenges.