Effects of Microplastic Pollution on Growth, Photosynthesis, and Nutritional Composition of Maize ( Zea mays L.)
Abstract
Microplastic (MP) contamination in agroecosystems is an increasingly recognized environmental concern, whereas its polymer‐specific impacts on plant growth and nutritional composition remain poorly understood. Our study aimed to evaluate how polymer type and concentration of MPs directly affect plant growth, physiological traits, and nutrient balance under hydroponic conditions. Maize ( Zea mays L.) seedlings were exposed to polypropylene (PP) and polyethylene (PE) MPs at two concentrations (50 and 200 mg L −1 ) in a hydroponic system, thus unravelling direct root–particle interactions from soil‐mediated effects. The experiment was independently repeated under similar conditions to validate the reproducibility of MP‐induced growth responses in maize. Across both independent experiments, MP exposure reduced shoot and root biomass, photosynthetic capacity, and carbon and nitrogen accumulation, with PP causing more negative effects than PE. Compared with the control, MP exposure decreased shoot Ca, K, Mg, Mn, and S concentrations by 7.5%–44.5%, 5.7%–21.1%, 19.5%–53.4%, 8.6%–39.1%, and 7.1%–26.3%, respectively. Shoot Cu was reduced by 9.8%–47.1%, whereas P decreased by 1.3%–11.8% depending on polymer type and dose. In contrast, shoot Zn increased markedly by 183.0%–322.6% under MP exposure. With a few exceptions, the patterns for root ionomes were generally similar to those of shoots, with reductions of nutrient uptake becoming more pronounced at higher MP doses. These changes led to severe ionic imbalances, which were evidenced by changes in elemental ratios like K:Ca and Zn:Fe, indicating disturbed nutrient homeostasis. Increasing MP concentrations increased membrane damage, as demonstrated by elevated electrolyte leakage and malondialdehyde concentrations, and reduced leaf water content, indicating enhanced oxidative and dehydration stress. Overall, MP toxicity exerted direct negative effects on maize growth, photosynthesis, and nutritional composition depending on polymer types and concentrations.