Chitosan nanoparticles alleviate nanoplastics toxicity by modulating polyamine metabolism and re-establishing redox homeostasis in maize seedlings

As an emerging pollutant, nanoplastics have the potential to negatively affect plant growth and nutrient absorption, ultimately resulting in reduced yield. Chitosan nanoparticles (CSNPs), a sustainable polymeric material, has been shown to improve resistance to various stressors. This study aims to elucidate the potential mechanisms by which CSNPs may alleviate the toxicity of polystyrene nanoplastics (PSNPs) in maize plants. The results demonstrate that CSNPs treatment significantly reduced PSNPs accumulation in maize leaf and root tissues by 32.1 % to 56.2 % (P < 0.05) compared to PSNPs exposure alone. Furthermore, CSNPs alleviated PSNPs induced phytotoxicity, as evidenced by increases in chlorophyll content, leaf area index, and photosynthetic rate by 108.7 %, 29.4 %, and 70.0 %, respectively, ultimately leading to a 72 % increase in total plant dry weight. Additionally, CSNPs systematically upregulated the expression of genes involved in polyamine biosynthesis, increased the activities of related enzymes, and inhibited the activities of polyamine degradation enzymes, resulting in a 36.6 % increase in total polyamine content. Additionally, CSNPs decreased the accumulation of reactive oxygen species and lipid peroxidation caused by PSNPs stress by modulating the antioxidant system. Collectively, our findings indicate that CSNPs mitigated the adverse effects of PSNPs on maize plants by regulating polyamine metabolism and reestablishing redox homeostasis.