Abstract: Invasive plants pose a major threat to global ecosystems, exhibiting broad adaptability to multifaceted abiotic stresses. To investigate whether root-shoot ratio (RSR) plasticity represents a consistent cross-stress mechanism underpinning invasion success, we integrated a meta-analysis of 87 studies (spanning drought, heavy metals, salinity, temperature, and nutrient deficiency) with targeted experiments under controlled drought and heavy metal stress. Meta-analysis revealed that invasive plants consistently increase RSR across multiple abiotic stresses (mean effect size: +0.45; P < 0.001), whereas native species showed no significant changes (-0.03; P = 0.72). Invasive RSR increased by 0.29-0.98 (P < 0.05) under specific stresses (e.g. drought: 0.42; heavy metals: 0.77), contrasting sharply with natives (significant only under nutrient deficiency: 0.61). While, total biomass, C/N/P stoichiometry, and microbial diversity showed no consistent stress responses. In our experimental validation, under drought, invasive Avena sativa increased RSR by 65.8-305.3% (competition) and 101.1-114.1% (monoculture); under cadmium stress (9-90 mg.kg^-1), invasives (Celosia argentea, Bidens pilosa, Ipomoea purpurea) increased RSR by 11.2-60.7%. These findings suggested that enhanced RSR plasticity is a key adaptive strategy in invasives, driven by greater phenotypic flexibility and reduced biotic constraints. Future research should explore molecular mechanisms (e.g. sucrose transporters) and interactive effects of multiple stressors. These findings illuminate invasion resilience and could inform strategies to bolster native plant resistance under global change.

Key words: Invasive species, Abiotic stress, Phenotypic plasticity, Resource allocation, Drought resilience, Heavy metal tolerance