Comparative Studies On Cold Resistance Of 20 Varieties Of Lagerstroemia Indica

Crape myrtle(Lagerstroemia indica L.) is an important ornamental tree species of Lythraceae. There are 21 species in Lythraceae in China,but only a little part of them were used in gardens in north of China because of the low temperature in winter.As a result,the research on cold resistence of Lagerstroemia indica is vitally necessary.In order to select more Lagerstroemia indica cultivars of superior ability of cold resistence,the research focused on the variation of membrane permeability,MDA content,relative water content,soluble protein content and soluble sugar content of Lagerstroemia indica twigs during low temperature stress.The main results were as follows:1.The determination results of membrane permeability show that:there were significant differences among 20 Lagerstroemia indica cultivars during low temperature stress,the membrane permeability of all the 20 Lagerstroemia indica cultivars were trending up during the low temperature stress,but the growth were different according to different cultivars.In the 5-year old cultivars,'Duo Hua Zi','Fen Jing','Fu Jian Za Zhong Bai','Zi Sha',were stronger than others,; 'Ping Zhi Fen','Ping Zhi Zi','Ping Zhi Bai' were the weakest;Between the 2-year-old cultivars, 'Bicolor'＞'Ai Zi Wei';these results were as same as the semilethal temperature LT₅₀.2.The determination results of soluble protein content of Lagerstroemia indica twigs during low temperature stress show that:the content of soluble protein and soluble sugar were increased during low temperature stress,The cultivars such as 'Duo Hua Zi','Fu Jian Za Zhong Fen','Fen Jing','Fu Jian Za Zhong Bai' had the strongest ability of cold resistence;'Za Zhong Fen','Ping Zhi Fen','Ping Zhi Zi','Ping Zhi Bai' were the weakest.Between the 2-year-old cultivars, 'Bicolor' had stronger ability of cold resistence than 'Ai Zi Wei'.3.The determination results of MDA content of Lagerstroemia indica twigs during low temperature stress show that:the content of MDA were increased during low temperature stress, meanwhile,The cultivars such as 'Fu Jian Za Zhong Bai','Fu Jian Za Zhong Fen',"Fen Jing' had the strongest ability of cold resistence;the cultivars such as 'Zi Zhao Yin Wei'.'Za Zhong Fen', 'Ping Zhi Fen','Ping Zhi Zi'.'Ping Zhi Bai' were the weakest;Between the 2-year-old cultivars, 'Bicolor" had the stronger ability of cold resistence than 'Ai Zi Wei'.4.The determination results of soluble sugar content of Lagerstroemia indica twigs during low temperature stress show that:the content of soluble protein and soluble sugar were increased during low temperature stress,The cultivars such as 'Duo Hua Zi','Fu Jian Za Zhong Fen','Fen Jing','Fu Jian Za Zhong Bai' had the strongest ability of cold resistence;the cultivars such as 'Ping Zhi Bai','Ping Zhi Fen','Ping Zhi Zi',were the weakest;Between the 2-year-old cultivars, 'Bicolor' had the stronger ability of cold resistence than 'Ai Zi Wei'.5.The determination results of relative water content show that:the relative water content of all the 20 Lagerstroemia indica cultivars were trending down during the low temperature stress, but the decreases were different according to different cultivars.The cultivars such as 'Fu Jian Za Zhong Bai','Fu Jian Za Zhong Fen','Fen Jing','Zi Jin'had the strongest ability of cold resistence;the cultivars such as 'Ping Zhi Fen','Ping Zhi Zi','Ping Zhi Bai' were the weakest; 'Bicolor' had stronger ability of cold resistence than 'Ai Zi Wei'..6.By using the method of fuzzy mathematics function,we can order the 20 Lagerstroemia indica cultivars according to the ability of cold resistence from the strongest to the weakest as follows:In the 5-year old cultivars,'Fu Jian Za Zhong Fen'＞'Fen Jing'＞'Duo Hua Zi'＞'Fu Jian Za Zhong Bai'＞'Zi Sha'＞'Duo Hua Fen'＞'Bing Qing Yu Die'＞'Zi Jin'＞'Za Zhong Fen'＞'Bai Yun Ying Xia'＞Z-1＞'Huan Fen Liu Yun'＞'Hong Die Fei Wu'＞'Zi Zhao Yin Wei'＞'Hong Ri Ying Xue'＞'Ping Zhi Bai'＞'Ping Zhi Fen'＞'Ping Zhi Zi.;Between the 2-year old cultivars,'Fu Se Ai Zi Wei'＞'Ai Zi Wei'According to the results of the research,the cultivars such as 'Fu Jian Za Zhong Fen','Fen Jing','Duo Hua Zi','Fu Se Ai Zi Wei','Fu Jian Za Zhong Bai' and'Zi Sha'can be recommended to cultivated in the gandens in north of China.