Effect of chronic and humped input of polystyrene microplastics on rice growth

The impact of microplastics (MPs) pollution on farmland is influenced by the type of rainfall and the hydrography of the site. However, it is not clear how the arrival of MPs to farmland through different input modes will affect plant growth. Here, we simulated the effects of polystyrene (PS) MPs chronic input (50 mg/L), humped input (0, 0, 0, 100, 250, 100, 0, 0, 0 mg/L) and without PS MPs input (control) on rice growth through hydroponic experiment. The results showed that the input mode of MPs had a significant effect on the growth of rice. Compared with the control, the chronic input reduced the fresh weight of rice roots, stems and leaves by 61 %, 60 % and 64 %, respectively. Humped input only had a significant effect on the fresh weight of rice roots and stems, which were reduced by 24 % and 17 %, respectively. Both PS MPs input modes significantly reduced the chlorophyll content of plants. However, the chronic input of PS MPs also stimulated the antioxidant system of rice, improved peroxidase (POD) activity, and changed the nutrient content in plant tissues. Overall, chronic input of PS MPs had a greater impact on rice growth. Therefore, it is crucial to consider the input modes of MPs when assessing their effects on plant growth. This study is the first to investigate the effects of different input modes of MPs on plant growth, providing new insights into the pathways through which MPs affect plants.