Effects Of NaCl Stress On Physiological Characteristics Of Vegetable Soybean During The Pod-Filling Stage

Vegetable soybean [Glycine max (L.) Merrill] is the nutritious vegetable with high profit. It has been a very important agricultural product in the areas where are middle-and-downriver of Yangtze River and south-and-east littoral of China. The areas are also the main areas for production, consumption and export of vegetable soybean. Soil salinization has seriously effected the production of vegetable soybean in their main production areas presently, so it is very important to study the salt tolerance physiology in vegetable soybean. There are lots of studies reported on salt tolerance physiology of G. soja and G. max in seedlings and seeds, but less reported in vegetable soybean. Using 'Lixiang95-1' as material, we compared the differences between the contrast and the salt stress vegetable soybean in physiological characteristics of leaves and seeds during the pod-filling stage. It helped us to find out the mechanism of vegetable soybean adapting to salt stress during the pod-filling stage. The results of this study were as follows:1. We studied the effects of 100 mmol·L^-1 NaCl stress on activities of antioxidant enzymes, contents of proline and malondiadehyde (MDA) in leaves of vegetable soybean during the pod-setting stage. The results showed that the activities of superoxide dismutase (SOD) and peroxidase (POD) was significantly increased under NaCl stress, and the former was more significantly, but the opposite was CAT activities. The content of proline was significantly increased under salt-stress, and the longer NaCl stress prolonged the more significantly the contents increased. The content of MDA early was also significantly increased, peaked at the 9th day, and then it came down.2. The effects of 100 mmol·L^-1 NaCl stress on the contents of Pro and PAs in leaves of vegetable soybean during the pod-filling stage. The results showed that the contents of three modal Put were increased firstly and than decreased under salt stress, but the content of Pro was increased significantly. The different modal Put changed to Spd and Spm during later stag, significantly did the free Put content.3. We studied the effects of 100 mmol·L^-1 NaCl stress on activities of antioxidant enzymes, the MDA content, the fresh weight and the dry weight in seeds of vegetable soybean during the pod-setting stage. The results showed that the fresh weight and dry weight were significantly decreased; the activities of SOD and CAT were decreased under salt stress, and the former was more significant; the POD activity was significantly increased under salt stress early stage, which peaked at the 3rd day and then decreased, but the activity in the salt stress was higher than the contrast; the MDA content in the salt stress is lower than the contrast early, but higher than the contrast after the 6th day.4. The effects of 100 mmol·L^-1 NaCl stress on the content of Pro and PAs in seeds of vegetable soybean during the pod-filling stage. The results showed that , the Pro content was increased firstly then decreased, which was higher in the salt stress than in the contrast; the contents of the three modal PAs were increased in seeds of vegetable soybean under salt stress: the contents of free Spm, conjugated Put, Spd, Spm and bound Put, Spd, Spm were significantly increased under NaCl stress.