Effects of seed dressing with xylose on wheat growth and the uptake of thiamethoxam and thifluzamide

In this study, thiamethoxam and thifluzamide were selected as representative pesticides to investigate the effects of exogenous compound seed dressing on wheat growth and pesticide uptake. Firstly, xylose was selected from nine candidate compounds for its significant enhancement of pesticide uptake in wheat in a soil-based pot experiment. Subsequently, we systematically evaluated the effects of xylose on wheat seed germination, growth, antioxidant enzyme activities, physiological stress indices (malondialdehyde MDA and proline Pro contents), as well as the uptake, translocation, and distribution of pesticides. The results showed that xylose significantly increased seedling fresh weight, root length, and stem diameter, and enhanced the uptake of key nutrients such as nitrogen, phosphorus, and potassium. When wheat seeds were treated with xylose at a rate of 0.45 mg/g dry seed, the uptake and translocation of thiamethoxam and thifluzamide in the plants were significantly enhanced. Among these, root accumulations of thiamethoxam and thifluzamide increased by 39.7% and 45.1%, and shoot accumulation increased by 79.6% and 76.2%, respectively, compared with the control. In addition, xylose treatment significantly increased the proportions of thiamethoxam and thifluzamide in the apoplasts and soluble fractions, while reducing their presence in cell walls. These results suggest that xylose enhances the intracellular mobility of both pesticides within the cells and facilitates their uptake and translocation across the plasma membrane, thus promoting the uptake and translocation of the two pesticides in wheat. Furthermore, xylose significantly enhanced the activities of superoxide dismutase (SOD) and peroxidase (POD), reduced MDA content, and increased Pro content. These changes suggest that xylose may help to mitigate pesticide-induced stress in wheat by activating the antioxidant system and osmotic adjustment mechanisms, while also synergistically enhancing the uptake of both pesticides. These findings will provide a theoretical basis for reducing the application rates of thiamethoxam and thifluzamide in wheat cultivation, and lay an important foundation for the future utilization of xylose in the development of novel pesticide synergists.