Study On The Evaluation Of Alfalfa (Medicago Sativa) Cold Resistance And Physiological Response In Autumn And Winter Cold Stress

The experiment had evaluated cold-resistance of 21 different alfalfa cultivars from home and oversea based on over winter rate, and discuss the relationship between biological property and over winter rate. Travois, Aurova alfalfa with different cold-resistance are chose to study on the adaptation from physiological aspect in the seasonal cold temperature stress in field experiment, analyzing the relationship between morphology and physiology character and cold-resistance. The main results are as follows:(1)21 different alfalfas cultivars were classified into 3 cold-resistance ranks, the material from Australia were all can't over winter, which are in the same weak cold resistance group. The result of analysis shows that Travois alfalfa promotes cultivation in Xianghuanqi area. There is positive relationship between output and over winter rate, the coraelation coefficient between single plant fresh weight, single plant dry weight and over winter rate is 0.640and 0.748 respectively. Leaf length and growth habit are significant negative associated with over winter rate, the coraelation coefficient is–0.582 and -0.587. That shows the cold adaptation of alfalfa in morphology.(2)The results of study on the adaptation of alfalfa in seasonal cold temperature stress showed that the activity of POD SOD and CAT increased firstly then decreased with the decrease of temperature and three kind of enzymes'activity were highest in early winter and decreased in late winter. From late summer to early winter, SOD activity increased 139.60% and 112.73% in Travios and Aurova alfalfa.The correlation analysis showed the activity of POD and SOD were significantly and (positively or negatively) correlation with winter surviving rate, the correlation coefficient is0.894 and 0.830. The enzymes activity of Travois kept higher level in seasonal cold temperature stress, while the enzymes activity of Aurova was low all the time and had significant difference with Travios alfalfa. It proved that it is veracious and reasonable for using enzymes activity in root crown to evaluate the cold resistance of alfalfa cultivars.(3)From late summer to early winter, alfalfa's enzyme system enhanced when it was stressed...