Abstract: In order to explore the physiological mechanism of low temperature stress in alfalfa (Medicago sativa L.), ‘Longmu 807’ alfalfa seedlings were used as materials. It was treated at 0,-2,-3,-4,-5℃ for 2 h. We analyzed the effects of osmotic adjustment substances,membrane permeability,membrane oxidation substances,antioxidant enzyme activities and metabolites in the leaves of alfalfa seedling under low temperature stress. The results showed that the content of soluble sugar,soluble protein,and proline,as well as the activities of peroxidase and superoxide dismutase increased first and then decreased with the increased temperature of low temperature stress,and reached the maximum value at -3℃,relative conductivity and the contents of malondialdehyde,hydrogen peroxide,oxygen free radical,and glutathione and the activities of catalase,ascorbate peroxidase and phenylalanine ammonia lyase showed an increasing trend,reaching the maximum value at -5℃,the content of chlorophyll,nitrate nitrogen and the activity of glycolate oxidase decreased. Through the principal component analysis of 16 indexes,we got 8 indexes with large eigenvectors. According to the membership function analysis of 8 indexes,the lowest temperature tolerance of ‘Longmu 807’ alfalfa seedlings was -3℃. In this study,soluble sugar,proline,soluble protein,relative electrical conductivity,peroxidase,catalase,phenylalanine ammonia lyase and glutathione had a good correlation with low temperature resistance.

Key words: Alfalfa, Low temperature stress, Physiological metabolism, Principal component analysis, Membership function analysis

摘要： 为了探讨苜蓿幼苗的低温胁迫生理响应机制,试验以‘龙牧807’苜蓿(Medicago Sativa L. ‘Longmu 807’)幼苗为材料，对其进行低温(0℃，—2℃，—3℃，—4℃和—5℃)处理，每个温度处理2 h，分析不同低温胁迫对苜蓿幼苗叶片的渗透调节物质、膜质透性、膜氧化物质、抗氧化酶活性和代谢物质的影响。研究结果表明：随着低温胁迫温度的增加，幼苗叶片中可溶性糖、可溶性蛋白、脯氨酸含量和过氧化物酶、超氧化物歧化酶活性呈先升后降的变化趋势，在—3℃达到最大值；相对电导率、丙二醛含量、过氧化氢含量、氧自由基产生速率、还原型谷胱甘肽含量和过氧化氢酶、抗坏血酸过氧化物酶和苯丙氨酸解氨酶活性呈升高变化趋势，在—5℃达到最大值；叶绿素、硝态氮含量和乙醇酸氧化酶活性呈降低变化趋势。通过对16个指标主成分分析，获得8个特征向量比较大的指标，对这8个指标进行隶属函数分析表明，‘LM807’苗期能耐受最低温度为—3℃。本研究中可溶性糖、脯氨酸、可溶性蛋白、相对电导率、过氧化物酶、过氧化氢酶、苯丙氨酸解氨酶和还原型谷胱甘肽与抗低温能力相关性比较好。

关键词: 苜蓿, 低温胁迫, 生理代谢, 主成分分析, 隶属函数