Abstract: The whole development of pollen,from the archesporial cell to mature tricellular pollen, was precisely studied at the ultrastructural level in IR36 (Oryza sativa L.). Some ultrastructural features were observed: (1) During meiosis, the microsporocytic cytoplasm presented "cytoplasm reorganization". This phenomenon appeared to faciliate the transfer from the sporophyte to gemetophyte. (2) At late tetrad stage, some deposits of wall were observed on the plasma membrane of tetrad cells. Up to early microspore stage, pre-exine began to develop. Then,the exine rapidly developed,and was essentially completed by late microspore stage. (3)At the middle microspore stage, the intermembrane space of microspore nuclear membrane expanded into a large "bubble", which was a universal phenomenon at this developmental stage. (4) Degeneration of tapetal cytoplasm began at the meiotic prophase(leptotene).The cytoplasm of tapetal cells took place dramatic changes at the ultrastructural level and the endoplasmic reticulum in the cytoplasm underwent highly active: when microsporocyte just formed, endoplasmic reticulum was sparse; following meiosis, endoplasmic reticulum population rapidly increased; Up to the middle microspore stage, there were a amount of endoplasmic reticulum. These changes reflected that endoplasmic reticulum may play a major role in the degenerating tapetum. (5)At the mature pollen stage, the wall of the middle layer and the inner tangential wall of the tapetum still remained and folded into a "compound wall" structure.

Key words: Oryza sativa, microsporogenesis, pollen development, tapetal development, ultrastructure

摘要： 运用透射电子显微镜技术，系统观察了水稻花粉及其花药壁层的发育过程，发现了一些新的现象：(1)小孢子母细胞减数分裂期间，伴随核内染色体变化的同时细胞质发生了“改组”现象，主要表现为核糖体分布密度的规律性变化，这标志着孢子体向配子体的转变。(2) 小孢子外壁的发育始于四分体晚期，最早表现在四分孢子质膜上沉积了少量的壁物质。随后沉积增多，至小孢子早期即形成初生外壁。此后外壁发育迅速，到小孢子晚期外壁已基本发育完成。(3)小孢子中期，小孢子细胞核的双层核膜局部分开，并逐渐扩张成一个“大泡”。核膜扩张在这一时期是一种普遍现象。(4)在花粉发育过程中，绒毡层细胞结构发生明显变化：小孢子母细胞形成之初，绒毡层细胞结构完整，内质网极少；随着减数分裂的进行，绒毡层胞质浓缩，细胞内出现“空腔”，内质网丰富；到了小孢子中期，仍有较多堆叠的内质网，此后逐渐消失。表明内质网在绒毡层的发育中起着重要的物质合成及运输作用。(5)花粉完全成熟时,花药中层细胞的壁以及绒毡层的外切向壁紧贴在一起，形成了一叠合的“壁”结构。

关键词: 水稻, 小孢子发生, 花粉发育, 绒毡层发育