低温对枇杷苗叶片与根尖的生理状况及超微结构的影响

Influence of Low Temperature on Physiological and Cell Ultrastructure of Leaves and Roots of Eriobotrya japonica Seedlings

摘要:

为探讨枇杷（Eriobotrya japonica）苗对低温伤害的响应，采用人工降温的方法，研究了‘解放钟’实生枇杷苗在低温胁迫下叶肉细胞与根细胞超微结构的变化，同时测定叶片褐变率、根系活力和细胞质膜相对透性（PMP）。结果表明，轻度低温（0℃）胁迫12 h，根系活力下降26.09%，叶片褐变率仅升高17.15%，根系PMP值持续升高而叶片呈下降趋势。电镜下观察，根细胞和叶肉细胞均有明显线粒体增加现象。0℃胁迫36 h根细胞发生胞间结冰，液泡消失、线粒体膨大变形、双层膜消失、嵴消失、细胞壁结构损伤，而叶肉细胞仅表现叶绿体破坏、淀粉粒变小，线粒体完整。重度低温（-3℃、-5℃）胁迫下，根细胞和叶肉细胞均发生细胞内结冰，且低温对根细胞的破坏程度明显高于叶肉细胞，根细胞比叶细胞发生细胞结冰的时间更早，受害更严重。这表明根细胞比叶肉细胞对低温更敏感，因此，在低温来临前对枇杷地下部采取保温措施，对缓解地上部低温伤害具有积极作用。

Abstract:

In order to understand the response to low temperature of loquat (Eriobotrya japonica) seedlings, the changes in cell ultrastructure of leaves and roots of ‘Jiefangzhong’ seedlings were studied under cold stress by artificial cooling, and leaf browning rate, root activity as well as plasma membrane permeabilities (PMPs) were measured. The results showed that the root activity decreased by 26.09%, and the leaf browning rate increased by 17.15% under light cold stress (0℃). The PMP of root increased and the PMP of leaf decreased. The number of mitochondria had significant increment in root and mesophyll cells under electron microscope, indicating that mesophyll cells and root cells resisted low temperature injury by enhancing respiration and energy metabolism. The intercellular freezing in roots was appeared at 0℃ for 36 h, causing vacuoles disappearance, mitochondrial enlargement, double membrane and cristae disappearance, cell wall structure damage, but in mesophyll cells, chloroplast destruction, starch grains became small, and mitochondria intact. Intracellular freezing would be caused in root cells and mesophyll cells at sever low temperature (-3℃, -5℃), and the damage degree in root cell wall under low temperature was more serious than that in mesophyll cell wall. The time of intracellular freezing in root cells was earlier than that in mesophyll cells. These were indicated that the root cell was high sensitive than mesophyll cell to low temperature. Thus, the insulation measure to underground parts of loquat before low temperature had positive roles in mitigating the injury to the aboveground parts.