植物叶片在低温条件下的结冰模式和机制的分析

发布时间：2018-04-14 11:01

  本文选题：冰冻胁迫 + 差热分析　； 参考：《鲁东大学》2017年硕士论文

【摘要】：低温条件下植物的结冰模式,即胞外或胞内结冰直接决定着细胞的生死,目前胞外结冰相关的直接证据还很少,特别是缺乏热力学的证据。本研究用高分辨率差热扫描和显微观察分析了女贞(Ligustrum lucidum)和冬青卫矛(Euonymus japonicus)叶片在降温过程中的结冰放热行为,发现了两种植物胞外结冰的热力学和组织结构变化的新证据。两种植物的活叶片在冷却过程中均呈现双放热峰,即双相结冰的特征,而预先冰冻杀死的叶片和叶片组织提取液浸润的滤纸片在同样的冷却过程中仅有一个快速的大的单放热峰,即单相结冰的特征。从开始结冰放热到到达放热峰顶点所需要的时间,女贞的新鲜离体活叶片为186秒,冰冻杀死叶片仅为11秒;对于冬青卫矛来说,从开始结冰放热到到达放热峰顶点所需要的时间,新鲜离体活叶片为141秒,冰冻杀死叶片仅为14秒。根据结冰放热量积分得到的体内总水分结冰一半的结冰弛豫时间,女贞的新鲜离体活叶片的结冰弛豫时间为189秒,女贞冰冻杀死叶片的结冰弛豫时间为73秒;冬青卫矛的新鲜离体活叶片的结冰弛豫时间为179秒,冰冻杀死叶片的结冰弛豫时间为87秒。女贞新鲜离体活叶片的过冷度为5.11℃,冰冻杀死叶片过冷度为5.72℃。冬青卫矛新鲜离体活叶片的过冷度为7.58℃;冰冻杀死叶片过冷度为7.36℃。这些结果显示两种植物的活叶片和冰冻杀死的叶片的过冷度没有明显的差别。实验从热力学上提供了两种高等植物叶片在低温条件下细胞外首先结冰的证据,并显示了两种植物的活叶片和冰冻杀死叶片在冷却过程中的相应结冰模式和过冷度的差别。目前尚未看到国际上有细胞外首先结冰的热力学证据和死活叶片结冰模式的热力学差别,因此实验结果为进一步深入了解植物的冰冻伤害机制提供了新的途径。显微观察也显示了结冰过程中,在细胞间隙中形成无色的大量冰晶和脱水收缩但细胞内容物未流失的染色细胞,显示出胞外结冰的特征。虽然差热分析在植物抗冻性的研究中已有了大量的报道,但目前尚未看到国际上有关于以高分辨率差热分析揭示细胞外结冰的热力学证据。实验结果为进一步深入了解植物的冰冻伤害机制提供了新的证据和研究方法。不同植物在温度下其光合作用和呼吸作用强度表现出明显差别。植物茎呈现出复杂的的结冰模式,其机理有待进一步研究。月季和冬青卫矛在不同梯度的低温环境下测得的电解质外渗率实验显示出冬青卫矛的半致死温度明显低于月季的半致死温度,表现出更强的抗冻性。
[Abstract]:The freezing pattern of plants under low temperature, that is, extracellular or intracellular ice, directly determines the cell life and death. At present, there are few direct evidences related to extracellular ice, especially the evidence of thermodynamics.In this study, the freezing and exothermic behavior of leaves of Ligustrum lucidum and Euonymus japonicus during cooling was studied by high resolution differential thermal scanning and microscopic observation. New evidences of thermodynamics and tissue structure changes of extracellular ice in two plants were found.The living leaves of the two plants show double exothermic peaks during cooling, that is, the characteristics of biphasic ice formation.In the same cooling process, there is only one fast and large single exothermic peak, that is, single phase ice formation, in the pre-freezing of the leaf and the filter paper infiltrated by the tissue extract of the leaf.Between the beginning of ice and heat and the time required to reach the top of the exothermic peak, the freshly detached leaves of the privet were 186.00 seconds, and the freeze-killed leaves were only 11 seconds; for the holly spear,From the beginning of freezing and heat release to the peak of exothermic heat, the fresh live leaves are 141 seconds, and the frozen leaves are only 14 seconds.According to the calorific integral of ice release, the ice relaxation time of the fresh living leaves of Ligustrum privet is 1890 seconds, and that of the leaves killed by freezing is 73 seconds.The freezing relaxation time of fresh leaves was 179 seconds, and that of frozen leaves was 87 seconds.The supercooling degree of fresh living leaves of Ligustrum privet was 5.11 鈩，

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