Studies On Comparision Of Cold Resistance On Different Fall Dormancy Alfalfa (Medicago Sativa)

In this study, we used the man-controlled temperature method and morphology and physiology techniques to determine the cold responses and discrepancies of alfalfa at different fall dormancy levels ,11 varieties were included , then discussed the relationship between the fall dormancy and cold resistance. The results are as follows:Under 4 low temperature stresses, the alfalfa's cold resistance at low level fall dormancy is stronger than the high level's, and -7℃with 6-hour low temperature stress is more suitable for the comparison of the different fall dormancy species'cold resistance.Under the cold stress, the membrane permeability of the fall dormancy alfalfa at different levels is bigger with the increase of the cold stress , and the increase of the fall dormancy alfalfa is lower than others. The whole trend of content of MDA in alfalfa at different fall dormancy is increasing under low temperature stress, and the content of MDA in different varieties is difference. The accumulation of MDA in high level fall dormancy alfalfa is more than others.Under the low temperature stress, the accumulation of the free proline with different stress intensity and cold resistance of materials shows some regularity. The accumulation of free proline is increase with lower temperature stress, the higher level of the fall dormancy will be less. The content of the proline has the biggest change while the extreme-non-fall dormancy type's change is the smallest.The low temperature stress makes the POD and SOD in different varieties of fall dormancy alfalfa significantly increase, especially the fall dormancy, but the non- and extreme- non fall dormancy is not very obvious.The distance of the seedling cotyledon to the first leaf of the fall dormancy was significantly positively related to the categories of different fall dormancy alfalfa. The distance of the seedling cotyledon to the first leaf among the difference categories was not significant. The distance between 1st-2nd leaf is positive related with fall dormancy of alfalfa and has reached a significant level. Through the specific analysis between different alfalfa variety's 1st-2nd leaf distance, only provide the preliminary estimates, it can not exactly mearsured.The CTR research in 5 varieties shows: Maverick ( FD=1 )﹥5426(FD=3)﹥Pierce(FD=8)﹥UC-1887(FD=10)﹥UC-1465(FD=11) , The fall dormancy categories show the good tightness of cell structure and cold resistance. Cell porosity shows:UC--1465(FD=11)﹥UC-1887(FD=10)﹥Pierce(FD=8)﹥5426(FD=3)﹥Maverick(FD=1)Extreme-non fall dormancy loose cell structure is better than other varieties.