Enantioselectivity of racemic metolachlor and S-metolachlor in maize seedlings.
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.
School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou, People's Republic of China.
Fei
F
Xie
Hui J
HJ
Liu
Wei D
WD
Cai
D000081:Acetamides / Q000737:chemistry / Q000494:pharmacology*; D006540:Herbicides / Q000737:chemistry / Q000494:pharmacology*; D009195:Peroxidase / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development; D013237:Stereoisomerism; D013482:Superoxide Dismutase / Q000378:metabolism; D003313:Zea mays / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development
D000081:Acetamides; D006540:Herbicides; D010940:Plant Proteins; D009195:Peroxidase; D013482:Superoxide Dismutase; C051786:metolachlor