Coexposure to polyvinyl chloride and acid rain mitigates cadmium toxicity in rice roots via a coordinated molecular...

Microplastics and acid rain (AR) are increasingly recognized as co-occurring pollutants in agricultural ecosystems; however, their combined effects on cadmium (Cd) toxicity in crops remain poorly understood. This study investigated the individual and combined effects of polyvinyl chloride (PVC) microplastics and AR on Cd toxicity in rice (Oryza sativa L.) roots under 0.3, 3, and 10 mg/L Cd exposure. PVC alone consistently reduced Cd accumulation and alleviated Cd-induced growth inhibition, whereas AR exerted concentration-dependent effects. Under high Cd stress (10 mg/L), PVC + AR coexposure induced a distinct, non-additive physiological response characterized by increased CAT and SOD activities (6.0-25.5% and 2.3-6.0%, respectively) and reduced MDA accumulation (23.1-29.8%) relative to Cd treatment alone. Three-way ANOVA further revealed significant interaction effects among Cd, PVC, and AR on root growth, oxidative regulation, and elemental homeostasis. Transcriptomic analysis and weighted gene coexpression network analysis (WGCNA) identified key modules associated with Cd responses, which were enriched in glutathione metabolism, antioxidant defense, ion transport, and stress signaling pathways. qRT-PCR analysis confirmed the suppression of Cd uptake-related transporters (OsNramp5 and OsHMA2) and the induction of detoxification-associated genes (OsGSTUs and OsNASs) under PVC and/or AR treatments. Collectively, these findings demonstrate that co-occurring environmental pollutants can trigger non-additive physiological and transcriptional responses in rice roots, providing new insights into plant adaptation to composite pollution and offering potential targets for ecological risk assessment and for improving crop resilience and food safety.