The Study On Changing Regularity Of Several Cold Resistance Indexes Of Alfalfa Under Low Temperature Stress

Alfalfa (Medicago sativa L.) is an important leguminous pasture widely cultivated in the world. Lower temperature in winter becomes a key point of restricting the alfalfa's growth in North China. In this paper, with the method of low-temperature stress, we mensurate the relative conductivity,the contents of Free Hydroxyproline and Malondialdehyde in the seedlings and ground levels of three kinds of cultivatable alfalfa with different winter hardiness(WL-525HQ, WL-323 vaccination, ZhaoDong alfalfa). The work is to analysis the relationship between three physiological index and alfalfa's hardiness. Research results show that:(1)With the method of low-temperature stress in the lab, the variation of the relative conductivity in the seedlings and ground levels of three kinds of alfalfa is coincident. The relation of the relative conductivity in size is WL-525HQ > WL-323 vaccination> ZhaoDong alfalfa, and what's more, the capability of alfalfa's hardiness in the actual measurement is also ZhaoDong alfalfa> WL-323 vaccination> WL-525HQ. It proves that theory is consistent with the practice. Hence one can see that, the relative conductivity can be used as the physiological index to evaluate the capability of alfalfa's hardiness.(2)With the material of seedlings in the lab, the conclusion that we mensurate contents of Free proline to judge the capability of alfalfa's hardiness is not consistent with the actual. So it will be proved by further experiments to make sure that if we can treat the variation of the contents of Free proline as the only physiological index to evaluate the capability of alfalfa's hardiness. However, with the material of the ground levels, the contents of the Free proline in size are ZhaoDong alfalfa> WL-323 vaccination> WL-525HQ. This is consistent with the actual. Then, we can set this method as the physiological index to evaluate the capability of alfalfa's hardiness.(3)In the whole process of the low-temperature stress, from the viewpoint of fluctuation range of the contents of Malondialdehyde in different alfalfa's seedlings and ground levels, the seedlings'range with the artificial low-temperature process is WL-525HQ > WL-323 vaccination> ZhaoDong alfalfa, and that in the ground levels is WL-525HQ > WL-323 vaccination> ZhaoDong alfalfa, meanwhile the ground levels'fluctuation range in the natural low-temperatrue is WL-525HQ > WL-323 vaccination> ZhaoDong alfalfa. This conclusion is consistent with the actual. It is clear that Malondialdehyde can be used as the physiological index to evaluate the capability of alfalfa's hardiness.