Toxicological effects and molecular metabolic of polystyrene nanoplastics on soybean (Glycine max L.): Strengthening defense ability by enhancing secondary metabolisms

Abstract

Nanoplastics, as emerging pollutants, have attracted worldwide concern for their possible environmental dangers. The ingestion and accumulation of nanoplastics in crops can contaminate the food chain and have unintended consequences for human health. In this study, we revealed the effects of polystyrene nanoplastics (PS-NPs; 80 nm) at different concentrations (0, 10, 100 mg L⁻¹) on soybean (Glycine max L.) seedling growth, antioxidant enzyme system and secondary metabolism. Using laser confocal microscopy, we demonstrated that the absorption and translocation of PS-NPs in soybean. Plant growth inhibition was observed by changes in plant height, root length, and leaf area after 7 days of exposure to PS-NPs. The effect of PS-NPs on photosynthetic characteristics was reflected by a significant reduction in total chlorophyll content at 10 mg L⁻¹. Activation of the antioxidant system was observed with increased malondialdehyde (MDA) content, and elevated activities of superoxide dismutase (SOD) and catalase (CAT). Non-targeted metabolomics analysis identified a total of 159 secondary metabolites, and exposure to 10 and 100 mg L⁻¹ PS-NPs resulted in the production of 61 and 62 differential secondary metabolites. Metabolomics analysis showed that PS-NPs treatment altered the secondary metabolic profile of soybean leaves through the biosynthesis pathways of flavonoid, flavone flavonol, and isoflavones, which is expected to provide new insights into the tolerance mechanisms of plants to nanoplastics. Overall, the results of this study deepen our understanding of the negative impacts of nanoplastics in agricultural systems, which is crucial for assessing the risks of nanoplastics to ecological security.