香榧营养苗端细胞组织分区的超微结构观察

AN ULTRASTRUCTURAL EVALUTION OF CYTOHISTOLOGICAL ZONATION IN THE SHOOT APICAL MERISTEM OF TORREYA GRANDIS

本文研究了榧树(Torreya grandis)成熟植株在季节生长中营养苗端的超微结构变化。各区域细胞的主要区别特征为:顶端原始细胞与亚顶端细胞相接的细胞壁较厚,液泡多分布于细胞游离面,质体中淀粉粒较小;亚顶端细胞壁较厚,液泡较大,质体中淀粉粒较大而多;周缘区细胞质体多不具淀粉粒,液泡也较小,胞间连丝丰富;肋状区细胞被大量的含淀粉质体及液泡占据了大部分空间,胞间连丝丰富。在季节变化的四个时期中,各区域细胞的亚显微结构特征亦不相同。休眠期各区细胞淀粉质体较发达,细胞壁较厚,液泡大;叶扩展期淀粉质体减少或消失;芽鳞形成期出现大量小液泡;新的顶芽形成期液泡增加,核糖体含量较高。讨论了各区域细胞核形态与其细胞活跃性的关系。

Ultrastructural differentiation of the shoot apex of growing vegetative buds of Torreya gran- dis was studied.On ultrastructural level,the shoot apex had the same zonation as in microst- rueture.The main characteristics of zonal differences were:the thickness of the cell walls, the size and the structure of the plastids,and the volume of the vacuoles.In the apical ini- tials,the walls between apical initials and subapical group cells were thick,the vacuoles were distributed mainly in the outer half of the cells,and there were small starch grains in plastids. The walls of the subapical group cells were thick,the vacuoles were large,and the plastids con- tain large starch grains.In peripheral cells,normally there were no starch grains in plas- rids,the vacuoles were smaller.But there were numerous plasmodesmata in the celi wall. in the rib meristem,the cells were occupied mainly by large vacuoles and rich starch contain- ing-plastids.Numnerous plasmodesmata were in the thicken walls.During the four periods of the seasonal activities,the ultrastrocture of the apical cells also changed.In resting period,in comparison with other periods,starch-plastids were more developed,cell walls were thicker,and the vacuoles were larger.In bud expansion period,S-plastids decreased or even disappeared, In bud scale formation period,large amount of small vacuoles appeared.In new bud forma- tion period,the size of the vacuoles increases,and many cup-shape plastids appear.The rela- tionships between the activities of the cells and the shape of the nucleus were also studied.