荔枝珍稀种质耐寒性鉴定及安全越冬的生理机制

为了探明7个荔枝珍稀种质的耐寒性及其安全越冬的生理机制，研究采用电导法测定不同低温处理条件下7个荔枝种质离体叶片冻害指数及伤害率的变化，拟合Logistic方程求得半致死温度，并分析荔枝在越冬期间叶片可溶性糖、可溶性蛋白质、游离脯氨酸、丙二醛（MDA）的含量，及超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性的变化规律。结果表明，7份试材叶片的冻害指数和伤害率随处理温度的降低而呈不同程度的上升，其中YA1和紫娘喜的耐寒性较强，而马贵荔和无核荔则较低。为了能够安全越冬，各种质通过生理调控来提高其耐寒性。随着气温的下降，叶片总含水量和自由水含量降低，束缚水和束缚水/自由水升高，气温回升后又出现逆转。越冬期间，各试材的可溶性糖、可溶性蛋白质、游离脯氨酸和MDA的含量均呈先上升后下降的变化趋势。SOD活性呈上升-下降-再上升的趋势，POD活性呈缓慢上升的趋势，CAT活性则无明显的变化规律。

Determination of Cold Tolerance and Physiological Mechanism of Safe Overwintering in Rare Litchi Germplasm

In order to investigate the physiological response of seven rare litchi germplasm to low temperature stress, freezing index and injury rate of vitro leaves were estimated under different low temperature treatments using electrical conductivity method. The semi lethal temperature was calculated according to the fitted Logistic equation and the dynamics of soluble sugar, soluble protein, free proline and malondiadehyde (MDA) contents and superoxide dismutase (SOD), peroxidase (POD) and catalase activity of leaf were analyzed during the winter. The results show leaf freezing index and injury rate with the decrease of the treatment temperature showed increased to some degrees in seven test material. Among them, YA1 and Ziniangxi were strong cold resistance, whereas Maguili and Wuheli were weak. To be able to live through the winter, each litchi germplasm would through physiological regulation to improve their resistance to cold. As temperatures drop, the total water content of leaves and free water content decreased, and bound water and bound water / free water were increased, reversal occurs after the temperature rose. During the winter, soluble sugar, soluble protein, free proline and MDA contents of each test material showed a trend of first increasing and then decreasing. SOD activity showed up-down-up again, POD activity increased slowly, CAT activity no obvious change law.