Paraquat toxicity is reduced by metal chelators in rice leaves

The possible mediatory role of transition metals in paraquat (PQ) toxicity in rice leaves was investigated. Metal chelators (2,2'-bipyridine, 8-hydroxylquinoline and 1,10-phenanthroline) reduced PQ toxicity in rice leaves. The reduction of PQ toxicity by 1,10-phenanthroline (PA) is closely associated with the decrease in lipid peroxidation and increase in activities of enzymes detoxifying active oxygen species. Our results support the notion that iron or copper plays a major role in PQ toxicity in detached rice leaves. Reduction of PQ toxicity by PA in detached rice leaves is most likely mediated through chelation of iron or copper and an increase in superoxide dismutase and glutathione reductase activities.