Effects Of Lower Temperature Stress On Activity Of Protective Enzymes In Alfalfa Seedlings And Crowns

Alfalfa (Medicago sativa L.) is an important forage legume grown across the world. Lower temperature in winter becomes a key reason, impeding the development of forage growing in North China. The protective enzymes is one of the main protective materials. Alfalfa in this study were three cultivars with different winter hardiness(WL-525HQ, WL-323 vaccination, ZhaoDong alfalfa), we accessed the activity of peroxidase(POD), superoxide(SOD) and their isozymes, content of protein under lower temperature to analysis their relationship with winter hardiness.Ihe results showed that:(1)In the process of lower temperature stress, the peroxidase(POD) activity in seedlings of nonhardy cultivar WL-525HQ and cultivar of intermediate hardiness WL-323vaccination expressed a change in volatility with lasting droping temperatures, ZhaoDong alfalfa, which is a high hardiness, expressed slow increasing trendency. The change of POD activity of crowns of three different alfalfa cultivars was basically coincident, from increasing to decreasing then to increasing. The change of POD activity of WL-525HQ and ZhaoDong is similar under wild temperature stress conditions.(2)With the temperature decreased, the superoxide (SOD) activity of seedlings of three alfalfa cultivars was in basically same trendency, showing double submit curve. At the beginning of low temperature stress, SOD activity in crowns increased for all cultivars. With the temperature decreasing, the trendency of SOD activity was from increasing to decreasing then to increasing.(3)The numbers of isozymes pattern of POD among different cultivars were no change under laboratory temperature stress. There were significant differences among ZhaoDong, WL-323 vaccination and WL-525HQ under wild temperature stress.(4)There was an isozymes pattern of SOD expressing among seedlings of three different cultivars under simulated temperature stress. There was two isozymes patterns among crowns of different cultivars. Also showed two isozymes patterns among crowns of different cultivars under wild temperature stress.(5)The contents of soluble protein in seedling under simulated temperature stress and crown under wild temperature stress of different alfalfa cultivars expressed increasing, the content of soluble protein expressed decreasing under simulated temperature stress.