Effects of dark treatment and regular light recovery on the growth characteristics and regulation of chlorophyll in water dropwort

Herbicides are largely used to control weed growth in wheat production. However, the application of some kind of herbicides usually aggravates the damage caused by low temperature, and is also a very common adversity during the early growth stages of wheat. In this study, we pre-treated wheat seedlings with the herbicide chemicals of isoproturon, fluroxypyr and fenoxaprop-P-ethyl, respectively and then exposed the plants to low temperature stress with different time intervals. The herbicides, especially isoproturon, significantly increased the negative effects of low temperature on electron transport rate, chlorophyll content, cell membrane stability as well as growth of wheat plants. Furthermore, the foliar application of ascorbic acid (AsA) decreased relative electric conductivity, reduced the content of malondialdehyde, and reduced the production rate of reactive oxygen species, these were in line with elevated activities of superoxide dismutase, catalase and peroxidase under the combined stress of isoproturon and low temperature, indicating that AsA effectively mitigated the sever oxidative stress induced by the combined stresses. Thus, some of the herbicides such as isoproturon are suggested to be very carefully used before the possibility of low temperature events. In case low temperature stress occurs after using of isoproturon, AsA could be used to partially alleviate the damage by the combined stress of isoproturon and low temperature in wheat production.