Abstract: This study was aimed to investigate the difference of cold resistance of alfalfa and its relationship with carbohydrate content in crown. The overwintering organs of Medicago falcata L.,‘Knight T’,‘Caoyuan No.3’,and ‘Magnum 3010’ alfalfa planted in Horqin sandy land were dug in the early stage of overwintering. Low-temperature treatment was performed in a programmed low-temperature treatment box. Alfalfa crown relative conductivity and soluble sugars content changes were detected. The lethal temperature (LT₅₀) was obtained using the relative electrical conductivity fitting Logistic equation. Correlation analysis was carried out on the LT₅₀ and sugar content. The results showed that the cold resistance of alfalfa was stronger than that of alfalfa,and the ranking cold resistance of different alfalfa varieties was ‘Gibraltar’ > ‘Caoyuan No.3’ > ‘Magnum 3010’ > ‘Knight T’. The correlation analysis showed that the content of alfalfa starch was negatively correlated with the cold resistance of alfalfa under -20℃ treatment (P<0.05). The content of fructose and sucrose under -20℃ and below temperature was significantly positively correlated with cold resistance of alfalfa (P<0.05). In summary,Fructose and sucrose are the protective substances of alfalfa during winter. The content of starch in alfalfa's crown under -20℃ treatment and the content of fructose and sucrose under -20℃ treatment can be used as the cold sensitive index of alfalfa.

Key words: Alfalfa, Crown, Carbohydrate, Cold resistance

摘要： 为探讨苜蓿（Medicago sativa L.）种类和品种的抗寒性差异及其与根颈糖类物质含量的关系，本研究在越冬前期挖取科尔沁沙地种植的黄花苜蓿（Medicago falcata L.）和‘骑士T’、‘北极熊’、‘草原3号’、‘巨能3010’紫花苜蓿的越冬器官，在程序式低温处理箱进行模拟低温处理，检测苜蓿根颈相对电导率及糖类物质含量变化，利用相对电导率拟合Logistic方程，获得半致死温度（LT₅₀），对LT₅₀和糖类物质含量进行相关性分析。结果表明：黄花苜蓿的抗寒性强于紫花苜蓿，不同紫花苜蓿品种的抗寒性为‘北极熊’ > ‘草原3号’ > ‘巨能3010’ > ‘骑士T’。相关分析表明，-20℃处理下苜蓿淀粉含量与苜蓿抗寒性呈显著负相关（P<0.05）；-20℃及以下温度处理下果糖和蔗糖含量与苜蓿抗寒性呈显著正相关（P<0.05）。综上所述，果糖和蔗糖是苜蓿越冬抗寒保护物质，-20℃处理苜蓿根颈中淀粉含量、-20℃及以下低温处理下果糖和蔗糖含量可以作为苜蓿衡量抗寒性强弱的敏感指标。

关键词: 苜蓿, 根颈, 糖类物质, 抗寒性