本研究对50份热带睡莲材料进行4 ℃、0 ℃、-6 ℃和-12 ℃的人工低温处理，测定了叶片相对电导率和半致死温度（LT₅₀），并对可溶性糖、丙二醛（MDA）和游离脯氨酸含量以及超氧化物歧化酶（SOD）活性进行了比较，并利用相关性分析和k均值聚类分析等方法对50份热带睡莲材料的耐寒性进行分级。结果表明：LT₅₀值可用于初步判断不同热带睡莲材料的耐寒性，其中，大部分热带睡莲材料的LT50值介于-5 ℃~0 ℃范围内，‘江南风韵’（‘Southern Charm’）的LT₅₀值最低（-5.85 ℃），‘潘燮’（‘Poonsub’）的LT50值最高（3.69 ℃）。随着温度降低，可溶性糖、MDA和游离脯氨酸含量以及SOD活性的变化趋势整体可分为3类：第1类各低温处理间的上述4个指标差异均不显著，总体变幅不大；第2类和第3类各低温处理间的上述4个指标的变化趋势各异且存在显著差异，总体变幅较大。相关性分析结果显示：热带睡莲材料的LT₅₀值与可溶性糖含量、MDA含量和游离脯氨酸含量呈极显著正相关，与SOD活性呈极显著负相关。进一步选取LT₅₀值、MDA含量、可溶性糖含量和SOD活性作为建立热带睡莲耐寒性评价体系的指标。k均值聚类分析结果显示：50份热带睡莲材料可分为4类，即不耐寒型、弱耐寒型、中等耐寒型和强耐寒型。综上所述，热带睡莲会通过多种生理生化反应来应对低温胁迫，总体上看，耐寒性越强的材料的可溶性糖和MDA含量越低，SOD活性越高；埃及白睡莲〔Nymphaea lotus （Linn.） Willdenow〕表现出强耐寒性，可以考虑作为耐寒性育种的优良亲本。

In this study, 50 tropical water lily materials were subjected to artificial low temperature treatments at 4 ℃, 0 ℃, -6 ℃, and -12 ℃, relative conductivity and semilethal temperature (LT₅₀) of the leaves were determined, contents of soluble sugar, malondialdehyde (MDA), and free proline and superoxide dismutase (SOD) activity were compared, and the cold tolerance of 50 tropical water lily materials was graded by using correlation analysis and kmeans cluster analysis， etc. The results show that LT₅₀ values can be used to preliminarily judge the cold tolerance of different tropical water lily materials, in which, the LT₅₀ values of most tropical water lily materials are within the range of -5 ℃-0 ℃, the LT50 value of ‘Southern Charm’ is the lowest (-5.85 ℃), while that of ‘Poonsub’ is the highest (3.69 ℃). With the decrease of temperature, the variation tendency of contents of soluble sugar, MDA, and free proline and SOD activity can be divided into three categories: the differences in abovementioned 4 indexes among each low temperature treatment of the first category are all not significant, and the overall variation degree is not great; the variation tendency of abovementioned 4 indexes among each low temperature treatment of the second and third categories are different and there are significant differences, and the overall variation degree is relatively great. The correlation analysis result shows that LT₅₀ values of tropical water lily materials show extremely significant positive correlations with contents of soluble sugar, MDA, and free proline, but show extremely significant negative correlation with SOD activity. LT₅₀ value, MDA content, soluble sugar content, and SOD activity are further selected as indexes to establish a cold tolerance evaluation system for tropical water lilies. The k-means cluster analysis result shows that 50 tropical water lily materials can be divided into four categories, namely non-cold tolerant type, weak cold tolerant type, medium cold tolerant type, and strong cold tolerant type. Taken together, tropical water lilies will cope with low temperature stress via multiple physiological and biochemical reactions, in general, stronger cold tolerant materials have lower contents of soluble sugar and MDA and higher SOD activity; Nymphaea lotus (Linn.) Willdenow exhibits strong cold tolerance, and can be considered as an excellent parent for cold tolerance breeding.