title: Enantioselective phytotoxicity of metolachlor against maize and rice roots.
abstract: Rac-metolachlor, a widely used chloracetanilide herbicide, is now being replaced by S-metolachlor in many countries. The enantioselective effects of rac- and S-metolachlor on root growth of maize and rice was studied in hydroponics. Visible morphological changes in root growth were observed after treatment with rac- or S-metolachlor. The main root and lateral roots were shorter in length, and the number of lateral roots was reduced. The half inhibition (IC(50,5d)) values for root length of rac- and S-metolachlor were 18.86 and 10.61 μM, respectively, for maize, and 7.33 and 5.35 μM, respectively, for rice. The root system activity after treatment with rac- or S-metolachlor was lower than that of the control, while the root membrane permeability was higher. The activities of superoxide dismutase, peroxidase, and catalase in the roots were lower after rac- or S-metolachlor treatment compared to those of the control, while the malondialdehyde content was higher. After rice was treated with 3.1 μM rac- or S-metolachlor, the cell wall separated from the cell membrane, and some destruction of nuclei and organelles was observed. The entire cell was destroyed after treatment with 12.4 μM rac- or S-metolachlor. The results showed that S-metolachlor has stronger effects than rac-metolachlor on crop roots.
authors.affiliation: School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310035, China. lhj@mail.zjgsu.edu.cn
authors.forename: Huijun
authors.initials: H
authors.lastname: Liu
authors.forename: Ruonan
authors.initials: R
authors.lastname: Huang
authors.forename: Fei
authors.initials: F
authors.lastname: Xie
authors.forename: Shuxian
authors.initials: S
authors.lastname: Zhang
authors.forename: Jiang
authors.initials: J
authors.lastname: Shi
mesh_terms: D000081:Acetamides / Q000633:toxicity*; D006540:Herbicides / Q000633:toxicity*; D046529:Microscopy, Electron, Transmission; D012275:Oryza / Q000187:drug effects*; D018517:Plant Roots / Q000187:drug effects*; D013237:Stereoisomerism; D003313:Zea mays / Q000187:drug effects*
chemical_list: D000081:Acetamides; D006540:Herbicides; C051786:metolachlor