淹水诱导小麦根通气组织形成和皮层细胞超微结构变化的研究

Aerenchyma Formation and the Ultrastructural Changes of Cortical Cells in Wheat Roots under Waterlogging

以淹水处理的小麦品种华麦8号(耐湿)和华麦9号(不耐湿)为材料,对次生根显微结构和皮层细胞超微结构变化进行研究,旨在揭示小麦次生根通气组织形成方式以及品种间耐湿差异的细胞学基础。结果表明,淹水144 h后,华麦8号次生根形成发达的通气组织且结构保持完整,而华麦9号次生根虽然也能够形成通气组织,但根的结构却失去完整性。次生根孔积率变化研究表明,华麦8号孔积率增长幅度大,华麦9号孔积率增长幅度小,且在同一淹水时期,华麦8号孔积率均大于华麦9号。对华麦8号皮层细胞超微结构变化的研究表明,淹水12 h后,细胞核变形;24 h后,染色体发生凝集,核膜变模糊,细胞壁变透明;48 h后,核膜破裂,细胞核解体,细胞壁被降解。同时对华麦8号皮层细胞核进行TUNEL标记,检测到淹水12 h后有少量细胞核呈TUNEL阳性;24 h后,阳性核数量显著增加;48 h后,皮层中阳性核数量达到最大。超微结构变化和TUNEL标记结果表明淹水诱导皮层细胞发生了程序化死亡。

The changes of microscopical structure of roots and the ultrastructure of cortical cells in two wheat cultivars, Huamai No. 8 （waterlogging tolerant） and Huamai No. 9 （waterlogging sensitive）, were studied for investigating the way of aerenchyma formation and the cytological basis of the waterlog- ging tolerance. The research of microscopical structure of roots revealed that the roots of Huamai No. 8 remained intact after 144 h of waterlogging, but the roots of Huamai No. 9 lost its integrity. The porosity changes in adventitious roots of the two cultivars revealed that the porosity in roots of Huamai No. 8 increased evidently,but there was no obvious increase in roots of Huamai No. 9. The porosity in roots of Huamai No. 8 was higher than that of Huamai No. 9 at the same stage of waterlogging. The ultrastructural changes of cortical cells in Huamai No. 8 were studied and the nucleus showed irregular shapes after 12 h of waterlogging. After 24 h,chromatin condensation to the nuclear periphery was observed and the cell wall became electron-transparent. After 48 h,the nuclear envelope ruptured,the nuclear and cell wall degraded. TUNEL labelling in roots of Huamai No. 8 revealed some TUNEL-positive nuclei in the cortex after 12 h of waterlogging. After 24 h, the positive nuclei increased significantly; After 48 h, the positive nuclei reached to the maximum. The results of ultrastructural changes and TUNEL labelling indicated that programmed cell death in cortical cells was induced by waterloging.