Effect of relieving-salt-stress and growth-promoting bacteria on germination of cotton seed under salt stress

The cotton seeds treated by Rs15-4 strain of relieving-salt-stress and promoting growth were sowed in vermiculite that contained the NaCl solution(0.7%). The changes of the cell membrane permeability, the contents of free proline, soluble protein, and soluble sugar of cotton cotyledon were determined during germination. The results showed that the cell membrane permeability of cotton seed treated by Rs15-4 strain was 26.15% lower than that of the control; the soluble protein content was obviously 29.30% higher than that of the control; the content of free proline enhanced 1.16 times compared to the control at the 7th day; the soluble sugar content was 10% higher than that of the control from the 2nd day to the 6th day, and tended to stabilization in cotton seeds cotyledon. At the same time, the activities of the catalase(CAT), the peroxidase(POD) and the superoxide dismutase(SOD) were determined. The results indicated that the peak value of activities of POD and CAT of cottonseeds treated by Rs15-4 strain appeared beforehand comparing with the control; the activity of SOD was greatly higher than the control. The germinating rate of cotton seeds treated by Rs15-4 strain was enhanced by 11.8%.