The growth and antioxidant defense responses of wheat seedlings to omethoate stress

Omethoate is one of the most powerful insecticides in China. Despite its high risks of human health and environmental safety, omethoate is still hard to be replaced because of its low price and high efficiency. To better understand physiological and biochemical responses to omethoate, we examined plant growth and antioxidative defense responses as well as omethoate uptake in wheat seedlings grown hydroponically with omethoate. Fresh and dry shoot weights were significantly higher at low concentrations (e.g. 0.1 g/L) than at high concentrations (e.g. 5.0 g/L). The same is true for the soluble protein content. On the contrary, contents of malondialdehyde, proline and omethoate, and activities of superoxide dismutase, peroxidase and ascorbate peroxidase in shoots increased linearly with increasing concentration of omethoate and with exposure time as well. However, catalase activity was increased dramatically at 0.1 g/L but sharply decreased by omethoate added at 1.0 g/L and above compared with that of the control. Taken together, these results support our hypothesis that antioxidative defense response is an important component of plant responses to omethoate and oxidative damage is the major cause for growth reduction of wheat exposed to higher concentrations of omethoate.