Zinc and ascorbic acid synergistically alleviate cadmium toxicity in wheat by modulating transporter genes and antioxidant defense.

Cadmium (Cd) contamination in agricultural soils poses a significant threat to global food safety and environmental quality. This study investigated the synergistic effects and mechanisms of exogenous zinc (Zn) and ascorbic acid (AsA) in reducing Cd toxicity in wheat (Triticum aestivum L. cv. Xinong 979). Wheat seedlings were exposed to 10 μmol·L-1 Cd and treated with 25 μmol·L-1 Zn, 200 μmol·L-1 AsA, or their combination. The combined application of Zn and AsA was more effective in mitigating Cd-induced growth inhibition than either treatment alone. Moreover, the combined treatment modulated the expression of key Cd transporter genes (TaIRT2, TaLCT1, TaHMA3, and TaNRAMP5), thereby influencing the uptake and distribution of Zn and Cd in plants. Statistical modeling, including partial least squares path modeling (PLS-PM) and random forest, identified root Cd parameters and leaf antioxidant activities as critical predictors of plant performance. Our findings demonstrate that the co-application of Zn and AsA alleviates Cd toxicity via a dual mechanism, namely "root shielding" (reducing Cd uptake) and "shoot detoxification" (enhancing antioxidant capacity), providing a promising strategy for reducing Cd accumulation in wheat.