Chlorpyrifos (CHP) contamination affects agricultural land and poses significant risks to plants and humans. Chitosan-oligosaccharide (COS) enhances plant resilience under stress and boosts the activity of enzymes metabolizing exogenous substances. This study aimed to explore the potential and mechanism of COS in mitigating CHP phytotoxicity and reducing CHP accumulation through both pot and field experiments. The results indicated that CHP exposure caused oxidative stress and decreased photosynthesis by 18.5 % in wheat. COS up-regulated the expression of antioxidant enzyme genes in CHP-stressed plants, resulting in a 12.1 %-29.4 % increase in antioxidant enzyme activity, which resulted in an 11.3 %-12.8 % reduction in reactive oxygen species (ROS) and an 11.5 %-14.7 % reduction in malondialdehyde (MDA) content in leaves and roots, respectively. Additionally, COS increased chlorophyll content by 6.6 % by regulating genes related to chlorophyll metabolism, enhancing photosynthesis by 13.6 %. COS also reduced CHP uptake and accelerated its metabolism by upregulating CYP450, GST, and lignin biosynthesis-related genes. Wheat treated with COS exhibited a 26.7 %-28.7 % reduction in grains' CHP content, resulting in a lower health risk index (HRI). These findings provide novel insights into the potential of COS in alleviating CHP phytotoxicity and reducing its accumulation.

Continuous misuse of difenoconazole (DFZ) results in farmland contamination, posing risks to crops and human health. Salicylic acid (SA) has been shown to enhance plant resistance and reduce pesticide phytotoxicity and accumulation. However, whether SA effectively reduces DFZ phytotoxicity and accumulation and its underlying mechanisms remain poorly understood. To address this, a short-term indoor experiment and a long-term outdoor pot experiment were conducted to evaluate the potential of SA to alleviate DFZ-induced phytotoxicity and its effects on DFZ uptake, translocation, metabolism, and accumulation. The underlying mechanisms were explored through physiological, biochemical, and gene expression analyses. The results showed that DFZ induced oxidative damage and reduced photosynthesis by 15.6% in wheat. SA upregulated the expression of genes encoding antioxidant enzymes (POD, CAT, SOD1, and SOD2) in the roots and leaves of DFZ-exposed plants, leading to a 7.5%-13.4% increase in antioxidant enzyme activities and a subsequent 9.7%-14.5% decrease in reactive oxygen species levels. Additionally, SA increased the total chlorophyll content by 16.3%, which was enhanced by regulating chlorophyll synthesis and degradation-related genes, thereby improving the net photosynthetic rate by 12.2%. Furthermore, SA upregulated the expression of lignin biosynthesis-related, CYP450, and GST genes, which reduced DFZ uptake and accelerated its degradation. Consequently, the wheat grain DFZ content decreased by 36.2%, thus reducing the health risk index. This study confirms the potential of SA to reduce DFZ phytotoxicity and accumulation. Based on these findings, we recommend using SA in DFZcontaminated areas to mitigate phytotoxicity and the associated human dietary exposure risks.