Comparative phytotoxicity of Rac-metolachlor and S-metolachlor on rice seedlings

Abstract

The toxicity of Rac-metolachlor and S-metolachlor on rice (IIYou92, Oryza sativa L.) seedlings was determined and compared in a hydroponics experiment. The elongation of shoot, main root, and the number of lateral roots were inhibited in both Rac- and S-metolachlor treatments. The 96h- IC50 of Rac- and S-metolachlor were 12.32 and 9.44 μM for shoot, and 4.69 and 1.75 μM for root, respectively. The content of chlorophyll a, chlorophyll b and total chlorophyll of leaf treated by Rac-metolachlor was higher than that treated by S-metolachlor. The activities of superoxide dismutase, peroxidase, cytochrome P450 2E1, glutathione S-transferase, and the content of glutathione increased after herbicide exposure, and the activities or the content was higher in the S-metolachlor treatment than in the exposure to Rac-metolachlor. Ultrastructural studies revealed that Rac- and S-metolachlor had adverse effects on leaf cells, and S-metolachlor treatment caused higher damage.

Keywords:

• Metolachlor
• comparative
• phytotoxicity
• rice growth

Acknowledgments

This work was supported by the National Natural Science Foundation of China (No. 20677049), Zhejiang Provincial Natural Science Foundation of China (No. Y5100376), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, and Personnel Administration, Zhejiang Province, China.