Effects of Lantana camara leaf extract on the activity of superoxide dismutase and accumulation of H2O2 in water hyacinth leaf.

Water hyacinth (Eichhornia crassipes) is one of the most productive plants, but is also a troublesome weed in the world. In order to protect the public water system from chemical herbicides pollution, biological method has been suggested to control the growth and the reproduction of this weed. Lantana (Lantana camara L.) is an important weed of the family Verbenaceae and its leaf extract is highly toxic to water hyacinth. The results of this study showed that the extract of lantana leaves suppressed the emergence of leaf buds of water hyacinth plant, and caused the decay of its leaves by foliar spraying. In addition, the increase of SOD activity in water hya- cinth leaves was in accordance with the accumulation of H 2O 2 and the increase in degree of membrane peroxidation, while the activity of catalase, which might remove the excessive H2O2 in water hyacinth leaves, was inhibited by treatment with lantana extract. At tissue level, high H2O2 histochemical labeling was detected in guard cells after treatment with lantana extract. This overpro- duction of H2O2 could kill the leaf cells and cause leaf necrosis in the treated plant. Therefore, the high toxicity of lantana leaf extract to water hyacinth might be due to oxidative stress.