School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou, People's Republic of China.
J Environ Sci Health B. 2010 Nov;45(8):774-82. doi: 10.1080/03601234.2010.515173.
Chiral herbicides may have enantioselective effects on plants. In this study, we assessed and compared the enantioselectivity of the chiral herbicides rac-metolachlor and S-metolachlor to maize seedlings. The superoxide dismutase activity (SOD) activity of roots and stem leaves treated by rac-metolachlor was 1.38 and 1.99 times that of roots and stem leaves treated by S-metolachlor. The peroxidase activity (POD) activity of roots and stem leaves was 1.48 and 2.79 times that of roots and stem leaves treated by S-metolachlor, respectively, while the catalase activity (CAT) activity was 4.77 and 8.37 times greater, respectively. The Hill reaction activity of leaves treated by rac-metolachlor were 1.45, 1.33, and 1.14 times those treated by S-metolachlor with treatments of 18.6, 37.2, and 74.4 μM. The differences observed between treatments of rac- and S-metolachlor were significant. Significant differences in maize seedling morphology were also observed between rac- and S-metolachlor treatments. The degradation rate of S-metolachlor in roots was greater than that of rac-metolachlor. The half-lives of rac- and S-metolachlor were 80.6 and 60.3 h at 18.6 μM; 119.5 and 90 h at 37.2 μM; and 169 and 164.8 h at 74.4 μM, respectively. Using the liquid chromatography-mass spectrometry method, hydroxymetolachlor, deschlorometolachlor and deschlorometolachlor propanol were considered to be possible metabolites. We determined the enantioselective toxicity of rac- and S-metolachlor to maize and speculated on the proposed metabolic pathway of metolachlor in maize roots. These results will help to develop an understanding of the proper application of rac- and S-metolachlor in crops, and give some information for environmental safety evaluation of rac- and S-metolachlor.
手性除草剂可能对植物具有对映体选择性效应。在本研究中，我们评估并比较了 rac-甲草氯和 S-甲草氯两种手性除草剂对玉米幼苗的对映体选择性。 rac-甲草氯处理的根和茎叶片中超氧化物歧化酶（SOD）活性分别是 S-甲草氯处理的 1.38 倍和 1.99 倍。根和茎叶片中的过氧化物酶（POD）活性分别是 S-甲草氯处理的 1.48 倍和 2.79 倍，而过氧化氢酶（CAT）活性分别是 S-甲草氯处理的 4.77 倍和 8.37 倍。 rac-甲草氯处理的叶片的希尔反应活性分别是 S-甲草氯处理的 1.45 倍、1.33 倍和 1.14 倍，浓度分别为 18.6、37.2 和 74.4 μM。 rac-和 S-甲草氯处理之间观察到的差异具有统计学意义。 rac-和 S-甲草氯处理之间也观察到玉米幼苗形态的显著差异。 S-甲草氯在根中的降解速度大于 rac-甲草氯。 rac-和 S-甲草氯在 18.6 μM 时的半衰期分别为 80.6 和 60.3 h；在 37.2 μM 时分别为 119.5 和 90 h；在 74.4 μM 时分别为 169 和 164.8 h。使用液相色谱-质谱法，认为羟甲草氯、去甲甲草氯和去甲甲草氯丙醇是可能的代谢产物。我们确定了 rac-和 S-甲草氯对玉米的对映体毒性，并推测了玉米根系中甲草氯的代谢途径。这些结果将有助于了解 rac-和 S-甲草氯在作物中的正确应用，并为 rac-和 S-甲草氯的环境安全评价提供一些信息。
