Two sugarcane varieties, GT17 and TT22, were used in this experiment. In the experiment, l00mg/L of ethephon and salicylic acid were sprayed on the sugarcane leaves in different sugarcane varieties at the end of tillering stage respectively. There are two controls, one is sprayed with water on the leaves under the condition of drought stress, the other is under normal conditions. Leaf Samples were collected to assay the oozing percentages in cells, contents of superoxide anion, chlorophyll a and...