Determination and Evaluation of Cold Resistance of 5 Populus×euramericana Clones

In order to compare the cold resistance of introduced Populus×euramericana clones, the annual dormant seedlings were used as experimental materials, and the relative conductivity was determined by artificial gradient cooling method at −15, −20, −25, −30, −35 ℃ for 24 hours. The activities of SOD, POD, CAT and the changes of malondialdehyde and soluble protein content were measured under the low temperatures, and use the fitted logistic equation to find the semi-lethal temperature. The evaluation indexes and cold resistance were ranked according to the membership function method and correlation analysis. The results showed that under low temperature stress, enzyme activity, malondialdehyde content and soluble protein content increased first and then decreased, and the differences among different clones were obvious. The semi-lethal temperature of clone Qg was the lowest and the value of membership function was the largest. The cold resistance index has a good comprehensive performance, and its cold resistance is the strongest; the protective enzyme activity is extremely significantly correlated, and there is a significant correlation between conductivity, malondialdehyde content and soluble protein content. Six indicators can be used to determine the cold resistance of poplar and provide a reference basis. According to the semi-lethal temperature and membership function values, the order of cold resistance is: Qg>Ta>Pa>Ti>La>Zhonglin 46>I-107.