Department of Bioagricultural Sciences and Pest Management, Colorado State University, 1177 Campus Delivery, Fort Collins, CO 80523, USA.
Department of Plant and Environmental Sciences, Clemson University, 171 Poole Agricultural Center, Clemson, SC 29634, USA.
Pestic Biochem Physiol. 2019 Sep;159:22-26. doi: 10.1016/j.pestbp.2019.05.009. Epub 2019 May 17.
Herbicide efficacy depends on herbicides crossing cell and organelle membranes. We evaluated an artificial membrane system to understand how herbicides cross biological membranes. This understanding aids in predicting herbicide behavior in planta and, consequently, efficacy, mode of action, and whether active transporter-based herbicide resistance mechanisms may be possible. Five herbicides with different log K and pK values were assessed: glyphosate, 2,4-D, clopyralid, sulfentrazone and glufosinate. The artificial membrane apparatus included four semipermeable membranes containing buffers with pH 2.7, 5 and/or 7.4, floating in a bath of diethyl ether. These conditions were based on the pH from different cellular compartments and the pK for these herbicides. Changes in herbicide concentration due to movement were measured using radioactivity or liquid chromatography mass spectrometry. In general, herbicide behavior followed the pattern predicted by their calculated pK and log K. Herbicides added to an acidic phase (pH 2.7) were more mobile than when they were added to the more basic phase (pH 7.4), except when herbicide's pK was lower than the pH of the starting phase. Clopyralid, 2,4-D, and sulfentrazone showed significant acid trapping behavior due to their weak acid functional groups. Sulfentrazone and 2,4-D had a high affinity for the nonpolar, diethyl ether bath, especially when they were protonated at low pH. Our findings illustrate the robustness of the system to provide predictions about herbicide behavior at the subcellular level.
除草剂的功效取决于除草剂是否能穿过细胞膜和细胞器膜。我们评估了一种人工膜系统，以了解除草剂如何穿过生物膜。这种理解有助于预测除草剂在植物体内的行为，从而预测其功效、作用模式，以及是否可能存在基于主动转运体的除草剂抗性机制。我们评估了 5 种 log K 和 pK 值不同的除草剂：草甘膦、2,4-D、氯吡嘧磺隆、唑嘧磺草胺和草铵膦。人工膜装置包括四个半透膜，其中含有 pH 值为 2.7、5 和/或 7.4 的缓冲液，漂浮在乙醚浴中。这些条件基于不同细胞区室的 pH 值和这些除草剂的 pK 值。使用放射性或液相色谱质谱法测量由于移动而导致的除草剂浓度变化。一般来说，除草剂的行为符合其计算的 pK 和 log K 预测的模式。添加到酸性相（pH 2.7）的除草剂比添加到碱性相（pH 7.4）的除草剂更具移动性，除非除草剂的 pK 值低于起始相的 pH 值。由于其弱酸性官能团，氯吡嘧磺隆、2,4-D 和唑嘧磺草胺表现出明显的酸捕获行为。当磺丁噁唑啉和 2,4-D 在低 pH 下质子化时，它们对非极性乙醚浴具有很高的亲和力。我们的发现说明了该系统的稳健性，可用于预测亚细胞水平的除草剂行为。
