【摘要】 进一步研究表明:未经干燥含水量38.3％的坡垒种子,其胚根尖细胞的超微结构良好,膜系统完整,各种细胞器能清楚辨认。经不同干燥处理后,含水量分别下降至30.7％、27.1％、22.7%、19.7％时,超微结构发生相应的不同程度变化和破损。与电镜观察试样相对应的胚轴—胚根切段培养试验中,其恢复生长和受害情况与发芽试验结果基本相同。在各含水量下,生长健壮或有生长表现的切段分别为100％、100％、70％、10％、0％。可以看出失水劣变中种子活力降低直至完全丧失发芽力,与细胞超微结构的变化和破损程度紧密相关。液泡膜或核膜的破裂可能是产生不可逆变化的临界点。更多还原

【Abstract】 In this present paper, the ultrastructural Changes in radicle-tip cells, the growth of radicle-hypocotyl cut off the tip for electron microscope observation and the vigor of Hopea hainanensis seeds during deterioration resulted from losing water were studied further. These results are summarized as follows: When the seed water content was reduced from 38.3% to 30.7%, the ultrastructural changes in radicle-tip cells of viable seed showed as follows: The ribosomes in cytoplasm and rough endoplasmic reticulum decreased obviously. Some ER gathered into parallel profiles, or some into circles. The plastid quantity decreased and the starch grains disappeared。The cytoplasm formed some bigger or smaller vesicles. Crista in some mitochdria were destroyed. The nuclei and nucleoli changed into various irregular shapes. It was proved that these changes were revesible by the tests of germination and radicle-hypoctyl culture. There were 26% of seeds, 30% of radicle-hypocotyl cuttings losing germination power and growth ability, when the water content of the sees was reduced to 27. 1%. Most ultrastructures in their radicle-tip cells were disintegrating. In those cells of which still kept germination power but their vigor with partial tissues injured reduced markedly, the ultrastructural changes were aggravated further.The membrane of nucleus had been damaged partially, mitochondria disintegrated inside, in some cells the ultrastructures were disintegrating completely. There were only 20% of seeds, 10% of radicle-hypocotyl cuttings which still kept germination power and more lower vigor, when the seed water content was redued to 22.7%. The ultrastructural changes in Their radicle-tip cells were similar to treatment No. Ⅲ but increase in degree. When the seed water content was continuously reduced to 19.7%, all seeds and radiclc-hypocotyl cuttings died. The ultrastructures of all the cells in their radicle-tip disintegrated completely, or only remained as a few recognizable remains.更多还原