Revealing the Selenium-Mediated Regulatory Mechanisms of P. stratiotes in Response to Nanoplastics Stress from Multiple Perspectives of Transcriptomics, Metabolomics, and Plant Physiology

As emerging pollutants, nanoplastics (NPs) are profoundly threatening aquatic ecosystems. However, the systematic response mechanisms of aquatic floating macrophytes to NP stress and the mitigation strategies of nanoselenium (Se) remain poorly understood. This study used <i>P. stratiotes</i>, a dominant species in freshwater ecological restoration, as the research object. By intervening in NP stress via foliar application of Se, the study systematically deciphered the plant's response and mitigation mechanisms to NPs pollution through integrating physiological and biochemical analyses, ultrastructural observation of cells, and transcriptomic and metabolomic multi-omics techniques. The results showed that NP stress significantly reduced photosynthetic pigment concentration and inhibited photosystem function in <i>Pistia stratiotes</i> L., disrupted energy metabolism homeostasis, and simultaneously induced an outburst of reactive oxygen species (ROS). It activated non-enzymatic antioxidant substances such as flavonoids and glutathione (GSH), as well as enzymatic defense systems including catalase (CAT) and peroxidase (POD), promoting the reprogramming of the plant's metabolic strategy from growth priority to defense dominance. At the transcriptomic level, NP stress significantly altered the gene expression profile, with core pathways enriched in photosynthesis antenna proteins and phenylpropanoid biosynthesis. Metabolomic analysis revealed significant differences in metabolites, with markedly upregulated contents of defense-related metabolites such as lipids and terpenoids. The intervention of NPs-Se effectively restored photosynthetic pigment contents and enzyme activities, alleviated cell membrane damage by repairing the photosynthetic apparatus, optimizing ribosome-mediated protein synthesis pathways, and strengthening the antioxidant defense network. Meanwhile, it regulated the expression of specific genes and the accumulation of core differential metabolites, reconstructed the balance between energy supply and defense investment, enabling the plant to achieve more efficient adaptive regulation. Multi-omics correlation analysis further confirmed that the responses of <i>P. stratiotes</i> to NPs and NPs-Se exhibited characteristics of coordinated regulation, highlighting the modular regulatory patterns of nano-stress responses. In conclusion, Se can effectively alleviate the stress damage of nanoplastics to <i>P. stratiotes</i> through multi-dimensional regulation, providing a key experimental basis and theoretical support for the ecological restoration of NP-polluted water bodies and ecological risk assessment.