Arbuscular mycorrhiza orchestrates phenotypic plasticity of a critical suite of functional traits in plants under vanadium stress.

Vanadium (V) pollution in soil is a serious problem in some parts of China. Arbuscular mycorrhizal fungi (AMF) have shown promise in improving the remediation of V-polluted soil, but their role in orchestrating the complex phenotypic plasticity of plants under V stress remains unclear. We conducted a pot experiment using the green foxtail (Setaria viridis) inoculated with or without Rhizophagus irregularis under three V levels (150, 500, 1000 mg kg-1). AMF significantly increased plant biomass, improved morphological traits, decreased V concentrations in soil and plants, and improved biological enrichment and translocation factors only at high V. In plant leaves, V was mainly distributed in cell walls and soluble fractions, and AMF reduced V in organelles and increased thiol compounds. AMF altered the relationships between plant fitness and key traits, and strongly regulated phenotypic plasticity indices (coefficient of variation [CV] and phenotypic plasticity index [PPI]). Principal component analysis (PCA) indicated AMF was the main driver of phenotypic differentiation. AMF may act as an important modulator of phenotypic plasticity, coordinating organ, subcellular and physiological responses to enhance V detoxification, providing a mechanistic basis for AMF-assisted phytoremediation.