Toxic effects and mechanisms of engineered nanoparticles and nanoplastics on lettuce (Lactuca sativa L.)

Engineered nanoparticles (ENPs) and nanoplastics (NPs) are typical nanoparticles in terrestrial environments. Till now, few studies have compared their toxicity and mechanism to plants. Here we investigated the effects of CuO, nZVI ENPs and polystyrene (PS) NPs on lettuce growth, metabolic functions, and microbial community structure. Results showed that low concentrations of nanoparticles decreased root biomass and promoted photosynthetic indicators, whereas increased reactive oxygen species (ROS) were detected in roots exposed to high concentrations of nanoparticles. High-dose CuO ENP exposure significantly raised the MDA content by 124.6 % compared to CK, causing the most severe membrane damage in the roots among the three types of nanoparticles. Although linoleic acid metabolism was down-regulated, the roots alleviated CuO stress by up-regulating galactose metabolism. Uptake of PS by roots similarly caused ROS production and activated the oxidative stress system by altering amino acid and vitamin metabolism. Faster microbial responses to nanoparticles were observed in the nZVI and PS networks. The root toxicity was indirectly mediated by ion release, NP uptake, or ROS generation, ultimately impacting root cell metabolism, rhizospheric microorganism and plant growth. These findings provide theoretical basis for assessing environmental impact of nanoparticles and their possible ecological risks.