Uptake kinetics and accumulation of pesticides in wheat (Triticum aestivum L.): Impact of chemical and plant properties
2021
Liu, Qianyu | Liu, Yingchao | Dong, Fengshou | Sallach, J Brett | Wu, Xiaohu | Liu, Xingang | Xu, Jun | Zheng, Yongquan | Li, Yuanbo
Plant uptake is an important process in determining the transfer of pesticides through a food chain. Understanding how crops take up and translocate pesticides is critical in developing powerful models to predict pesticide accumulation in agricultural produce and potential human exposure. Herein, wheat was selected as a model plant species to investigate the uptake and distribution of eleven widely used pesticides in a hydroponic system as a function of time for 144 h. The time-dependent uptake kinetics of these pesticides were fitted with a first-order 1-compartment kinetic model. During 144 h, flusilazole and difenoconazole, with relative high log Kₒw (3.87 and 4.36, respectively), displayed higher root uptake rate constants (k). To clarify the role of root lipid content (fₗᵢₚ) in plant accumulation of pesticides, we conducted a lipid normalization meta-analysis using data from this and previous studies, and found that the fₗᵢₚ value was an important factor in predicting the root concentration factor (RCF) of pesticides. An improved correlation was observed between log RCF and log fₗᵢₚKₒw (R² = 0.748, N = 26, P < 0.001), compared with the correlation between log RCF and log Kₒw (R² = 0.686, N = 26, P < 0.001). Furthermore, the hydrophilic pesticides (e.g. log Kₒw < 2) were found to reach partition equilibrium faster than lipophilic pesticides (e.g. log Kₒw > 3) during the uptake process. The quasi-equilibrium factor (αₚₜ) was inversely related to log Kₒw (R² = 0.773, N = 11, P < 0.001) suggesting a hydrophobicity-regulated uptake equilibrium. Findings from this study could facilitate crop-uptake model optimization.
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