Antioxidant defense network and toxicity risk assessment in Panax species under heavy metals stress

The continuous accumulation of heavy metals (HMs) in soil poses a serious threat to the quality and safety of medicinal plants. However, a systematic assessment of the responses of the antioxidant defense system in Panax medicinal plants under HM stress is still lacking. In this study, we integrated 641 pairs of control-observation data from global sources and systematically analyzed the response characteristics of Panax medicinal plants under HM stress using meta-analysis and machine learning modeling. The results showed that HM exposure significantly promoted catalase activity (11.63%, P < 0.05), gene expression levels (56.10%, P < 0.01), and heavy metal accumulation (218.55%, P < 0.001) in Panax medicinal plants, ultimately leading to irreversible biomass loss (-29.62%, P < 0.001). The full RF model exhibited good fit (R² = 0.66, RMSE = 0.44), while a reduced model with only environmental predictors showed low predictive performance (R² = 0.18). Therefore, the analysis is more appropriate for identifying the relative importance of modulating factors than for robust toxicity prediction. SHAP analysis and PLS-PM revealed that HM concentration (12.33%), geographical characteristics (11.93%), and duration of metal pollution exposure (5.53%) are key factors regulating the antioxidant defense system of Panax medicinal plants. This study elucidates the response mechanisms of the antioxidant defense system in Panax medicinal plants under HM stress, providing a scientific basis for toxicity risk assessment, resistant variety screening, and the development of field regulation strategies.