From invasion to remediation: Phytolacca americana outcompetes congeners through superior cadmium hyperaccumulation and stress resilience in contaminated soils

Soil heavy metal (HM) pollution and biological invasions synergistically threaten ecosystem stability by impairing plant growth and reproduction. This study investigates the differential adaptability of the invasive Phytolacca americana and its congeneric relatives (P. icosandra and native P. acinosa) under cadmium (Cd) stress. Plants were cultivated in soils with Cd concentrations of 0, 2, 8, and 32 mg kg^-1, and their growth, physiological traits, antioxidant responses, and Cd accumulation were analyzed. Results demonstrated that P. americana exhibited enhanced morphological traits (plant height, leaf area), photosynthetic efficiency, and reproductive output (fruit weight and biomass) under Cd stress, whereas P. icosandra and P. acinosa displayed significant declines. Antioxidant enzyme activities (superoxide dismutase, catalase) and proline content in P. americana increased markedly (e.g., 77.72 % proline elevation under high Cd), mitigating oxidative damage. Additionally, P. americana showed superior Cd bioaccumulation, with translocation factor (TF) 1.25- and 2.08-fold higher than P. icosandra and P. acinosa, respectively, alongside stable bioconcentration factors (BCF) under high Cd. In contrast, P. icosandra exhibited concentration-dependent Cd tolerance, while P. acinosa prioritized root Cd sequestration. Notably, P. americana maintained growth-reproduction equilibrium without trade-offs, a trait absent in its congeners. These findings highlight P. americana's robust Cd adaptability and hyperaccumulation potential, offering insights for ecological restoration of contaminated soils. However, molecular mechanisms and multi-metal interactions warrant further exploration.