Effects of micro- and nano-plastics on accumulation and toxicity of pyrene in water spinach (Ipomoea aquatica Forsk)

Micro- and nano-plastics (MNPs) in terrestrial ecosystems are attracting increasing attentions. However, the studies of MNPs on the accumulation and migration of organic contaminants in edible plants are relatively scarce. Here, we investigated the impacts and mechanisms of MNPs of different concentrations and sizes on the uptake and toxicity of pyrene in water spinach. The results showed that MNPs had a promotion effect on the uptake of pyrene in various parts of water spinach, leading to the continuous accumulation of pyrene. The promotion effect of high concentration microplastics (MPs, 10 μm) is stronger than that of nanoplastics (NPs, 100 nm). The co-exposure of MNPs and pyrene increased the contents of malondialdehyde (MDA) in water spinach and aggravated the damage of lipid peroxidation. The co-exposure of MNPs and pyrene induced the increase of photosynthetic pigment contents and enhanced chloroplast activity. In addition, the co-exposure stimulated the overexpression of psbA and rbcL genes related to photosynthetic pigments, resulting in genotoxicity of water spinach. This study emphasized that the co-exposure of MNPs and pyrene caused harmful effects and high concentration of MPs caused greater toxicity to water spinach than NPs.