Effects of polyethylene microplastics, arsenic, and their combined contamination on maize seed germination

This study investigated the individual and combined effects of polyethylene microplastics (mPE) and arsenic (As) on maize (<i>Zea mays L.</i>) seed germination. Maize seeds were exposed to mPE (0.1%, 0.5%, 1%, and 2%) and As (1, 2, 5, and 10 mg/L) to assess changes in germination indices (germination rate, vigor index, germination index, germination energy, root/shoot length, and fresh/dry weight) and antioxidant enzyme activities [peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT)]. Low concentrations of mPE (0.1%) or As (1 mg/L) were found to slightly promote germination rate, vigor index, and root/shoot length. In contrast, high concentrations (1-2% mPE; 10 mg/L As) significantly inhibited germination indices. Under combined exposure, 0.1% mPE with all concentrations of As synergistically enhanced the vigor index and shoot length, whereas 2% mPE with all concentrations of As exhibited antagonistic effects. Low concentrations of mPE (0.1-0.5%) or As (1 mg/L) individually enhanced POD, SOD, and CAT activities. In contrast, high concentrations of As reduced POD and SOD activities, suggesting potential impairment of the antioxidant system. The interactions between mPE and As exert concentration-dependent effects on maize germination and antioxidant defense. These results provide a basis for the risk assessment of combined mPE and As contamination in agricultural ecosystems.