Oxidative injury induced by the herbicide quinclorac on Echinochloa oryzicola Vasing. and the involvement of antioxidative ability in its highly selective action in grass species

摘要

To investigate the possible involvement of antioxidative ability in the highly selective action of the herbicide quinclorac (3,7-dichloro-8-quinolinecarboxylic acid) in grass species, quinclorac-induced oxidative injuries and the activities of the antioxidative enzymes superoxide dismutase (SOD, EC 1.15. 1.1). catalase (CAT, EC 1.11. 1.6), ascorbic acid peroxidase (APX, EC 1.11. 1.11), and glutathione reductase (GR, EC 1.6.4.2) were studied in tolerant rice (Oryza sativa L. cv. Nipponbare) and a particularly susceptible grass weed, Echinochloa oryzicola Vasing. There were no significant differences in total chlorophyll content, formation of thiobarbituric acid-reactive substances (TBARS), and ethane and ethylene productions between 1 muM quinclorac-treated and control seedlings of rice both under continuous light and dark conditions. In contrast, the chlorophyll content in leaves decreased, and TBARS formation in shoots and ethane evolution increased in quinclorac-treated E. oryzicola seedlings under continuous light for 24 h. These changes were not observed in the dark, indicating that light enhanced the selective activity of quinclorac between rice and E. oryzicola. alpha-Tocopherol (alpha-TOH), a free radical scavenger, significantly suppressed quinclorac-induced TBARS formation in shoots and chlorophyll loss in the leaves of E. oryzicola. Antioxidant enzyme assays showed that the constitutive activities of SOD, CAT, APX, and GR enzymes in the shoots of E. oryzicola were lower than those in rice. Furthermore, there were significant correlations between the constitutive activities of APX and GR in shoots and chlorophyll content (% of control) in leaves after rice, corn (Zea mays L. cv. Honey Bantam), E. oqzicola, E. crus-galli Beauv. var. crus-galli, and E. crus-galli var. formosensis Ohwi were treated with quinclorac. These results suggest that the difference in hereditary antioxidative ability is one factor that results in the particularly high selectivity of quinclorac between rice and E. oryzicola. (C) 2004 Elsevier Ireland Ltd. All rights reserved.