Effects of soil thickness on the senescence of flag leaf after anthesis and yield in dry land wheat

With the increase of soil thickness ,the activity of superoxide dismatase(SOD) and catalase(CAT)、and the soluble protein content in wheat flag leaf increased, and the content of malondiadehyde(MDA) in wheat flag leaf decreased,and the yield increased. The thinner the soil was,the rapider senescence of flag leaf was. From the total soil layer,because of insignificant difference between treatment 3(160 cm) and control(200 cm), and significant difference between treatment 1(80 cm)、treatment 2(120 cm) and control,the 160cm of soil thickness could be as index for delaying senescence,and the basis for taking administration programme, and gainning high yield and high efficiency.