Exogenous spermidine mitigates bisphenol A-induced phytotoxicity in Syngonium podophyllum through antioxidant defense...

Bisphenol A (BPA), a widespread endocrine-disrupting contaminant, can induce oxidative toxicity and metabolic disturbances in plants. In this study, Syngonium podophyllum was used as a model plant to investigate the protective effects and underlying mechanisms of exogenous spermidine (Spd, 0.5 mmol L^-1) under BPA exposure (30 mg L^-1). The results showed that BPA toxicity significantly inhibited photosynthetic performance and induced the accumulation of reactive oxygen species (ROS) and lipid peroxidation in Syngonium podophyllum. Foliar application of Spd effectively enhanced photosystem stability, reduced electrolyte leakage rate, the levels of ROS and malondialdehyde (MDA), and regulated antioxidant enzyme activities and osmolyte contents, thereby alleviating oxidative damage. In addition, Spd increased free polyamine levels in leaves and restored the activities of polyamine oxidase (PAO) and diamine oxidase (DAO), suggesting that Spd-mediated polyamine homeostasis is closely associated with redox regulation under BPA exposure. Molecular docking revealed different binding characteristics of Spd and BPA toward PAO and DAO proteins. These findings suggest that polyamine-redox coordination is associated with the Spd-mediated alleviation of BPA-induced phytotoxicity.