Mechanistic insights into the effects of micro- and nano-plastics on cherry radish physiology and organic compound distribution at the soil-root interface.

Plastics are extensively applied in agricultural production, and exposure of crops to micro- and nano-plastics (MNPs) can markedly affect crop health. However, current understanding of the effects of particle size and concentration on the physiological and biochemical responses of plants remains limited. In this study, the effects of polyethylene micro-plastics (2 μm) and nano-plastics (200 nm) at varying concentrations in cherry radish were investigated. Plant biomass, physiological and biochemical responses, and the microspatial distribution and transport behavior of organic components at the soil-root interface were evaluated. The results demonstrated that high concentrations (150 mg/kg) of both micro- and nano-sized plastic particles significantly inhibited plant growth and photosynthetic performance, including reductions in chlorophyll content, net photosynthetic rate, and stomatal conductance. Notably, stress resistance indicators, such as soluble protein and soluble sugar, were affected, particularly at higher concentrations. SEM analysis directly verified the attachment of micro-plastic particles to root surfaces, whereas nano-particles were capable of penetrating root tissues. Synchrotron radiation-based FTIR imaging enabled in situ visualization of functional group distributions within the soil-root microenvironment, and semi-quantitative analysis further revealed a significant increase in carboxylic functional groups under nanoscale plastic exposure. This study also proposed a novel strategy to characterize the distribution and interactions of organic components within plant roots under MNP-induced stress. Overall, these findings offer new insights into the biological impacts and translocation potential of MNPs in crops, emphasizing their potential risks to agricultural production.