School of Public Health (Shenzhen), Sun Yat-sen University, China.
J Environ Manage. 2021 Oct 15;296:113180. doi: 10.1016/j.jenvman.2021.113180. Epub 2021 Jul 2.
To evaluate the impact of the phloem flux on the pesticide uptake process in potatoes, this study developed a phloem-adjusted model based on the classic model that focuses mainly on the diffusion process. To achieve high-throughput simulations, we introduced an approximate method to convert the phloem flux transport process into a simple specific uptake rate of pesticides. In comparison to the classic model (non-phloem model), the phloem-adjusted model generated higher pesticide concentrations and bioconcentration factors (BCFs) in potatoes, owing to the additional pesticide uptake route introduced to the adjusted model. However, the simulation, which was conducted for 740 pesticides, indicated that for most pesticides, the phloem flux route did not contribute a significant portion of the pesticide uptake to potato tubers compared with the soil diffusion route. This was further characterized, using the differential factor (DF), to evaluate the difference in the simulated results between the proposed model and classic models. The largest DF (~0.11) was obtained for pesticides with moderate lipophilicity (i.e., log K of 3.0), indicating that only a difference of 10% was generated between the two models. The 10% increase in pesticide concentration (or BCFs) in potatoes, simulated by the phloem-adjusted model, was within the acceptable uncertainty interval of the classic model, thus confirming the validity of using the classic model to predict the pesticide uptake process in potato tubers. However, we found that the negligibility of the phloem flux route was not merely due to hydrophobicity (i.e., hypothesis of the classic model), but was related to the i) plant physiology of potatoes, ii) lipophilicity of a pesticide, and iii) the diffusivity of a pesticide in water. Although future studies on pesticide concentrations in phloem sap and the dynamic growth of potatoes need to be undertaken, the model developed in this study reveals a more comprehensive pesticide uptake process in potatoes, which can promote the understanding of the pesticide uptake mechanism in potatoes.
为了评估韧皮部液流对马铃薯中农药吸收过程的影响，本研究在主要关注扩散过程的经典模型基础上，建立了一个韧皮部调整模型。为了实现高通量模拟，我们引入了一种近似方法，将韧皮部液流运输过程转化为简单的农药特定吸收速率。与经典模型（非韧皮部模型）相比，由于调整模型中引入了额外的农药吸收途径，韧皮部调整模型生成的马铃薯中农药浓度和生物浓缩因子（BCF）更高。然而，对 740 种农药进行的模拟表明，对于大多数农药来说，与土壤扩散途径相比，韧皮部液流途径对马铃薯块茎的农药吸收贡献不大。这进一步通过差异因子（DF）来表征，以评估提出的模型与经典模型之间模拟结果的差异。对于中等亲脂性（即 log K 为 3.0）的农药，DF 最大（~0.11），表明两个模型之间仅产生 10%的差异。与经典模型相比，韧皮部调整模型模拟的马铃薯中农药浓度（或 BCFs）增加了 10%，这在经典模型的可接受不确定性范围内，从而证实了使用经典模型预测马铃薯块茎中农药吸收过程的有效性。然而，我们发现韧皮部液流途径的可忽略性不仅仅是由于疏水性（即经典模型的假设），还与 i）马铃薯的植物生理学、ii）农药的亲脂性和 iii）农药在水中的扩散性有关。尽管需要进一步研究韧皮部液流中的农药浓度和马铃薯的动态生长，但本研究中建立的模型揭示了马铃薯中更全面的农药吸收过程，这有助于理解马铃薯中农药的吸收机制。
