Uptake kinetics and distribution of flupyrimin by rice (Oryza sativa L.): Effects of subcellular fractionation and soil factors

Flupyrimin is an emerging neonicotinoid insecticide primarily used to control rice planthoppers. However, knowledge gaps exist regarding its uptake and transport in rice planting systems. Elucidating the absorption and distribution properties of flupyrimin in rice will help assess the potential risks of human exposure to flupyrimin via the food chain. Here, we studied the uptake kinetics and transport mechanisms of flupyrimin in rice plants grown under hydroponic and soil conditions. The hydroponic experiment indicated that flupyrimin was easily taken up by rice roots via a symplastic passive diffusion process and was mainly distributed in the cell soluble fractions (50.6 %－88.0 %). Compared with transportation from the roots to the stems, flupyrimin was ultimately transported from the stems to the leaves with a greater translocation factor (TF) (TFLeave/Stem = 27.8 > TFStem/Root = 3.1). In rice-soil systems, the accumulation of flupyrimin by rice plants is influenced primarily by the soil organic matter content, which leads to increased adsorption of flupyrimin onto soils (R2 > 0.897, P < 0.014). Interestingly, the concentration of flupyrimin in rice was significantly positively correlated with its amount in the soil pore water (CIPW) (R2 > 0.967, P < 0.003), indicating that the uptake and accumulation of flupyrimin in rice planting systems can be estimated by CIPW. These findings enhance our knowledge of flupyrimin absorption and distribution in rice plants from treated soils and are important for guiding its field application and conducting environmental risk assessments.