甘薯绒毡层细胞的超微结构研究

从个体发育看,甘薯绒毡层细胞的结构具有以下主要特点:①小子孢母细胞时期,除细胞具有丰富的内质网、高尔基体、核糖体、线粒体等细胞器外,最明显的特征是细胞质积累大量的电子致密的淀粉粒.到减数分裂后期,淀粉粒全部分解,而脂质体的数量和体积随淀粉粒的分解而增加,这表明脂质体的形成与淀粉粒密切相关.②小孢子母细胞减数分裂时期,绒毡层细胞质中的内质网和高尔基体形成的囊泡状结构增加,线粒体内沉积电子致密物质.在这个时期,内质网和线粒体分别参与孢粉素颗粒和原乌氏体的形成.③小孢子发育至成熟花粉粒时期,除线粒体继续形成原乌氏体外,脂质体首先分解形成与孢粉素颗粒和原乌氏体大小相似的囊泡或小脂质体,然后分别沉积嗜锇物质而形成孢粉素颗粒和原乌氏体.孢粉素颗粒、原乌氏体和乌氏体的数量随脂质体的退化而迅速增加,表明质质体与孢粉素颗粒和原乌氏体的形成密切相关.

INVESTIGATION ON THE ULTRASTRUCTURE OF THE TAPETUM IN IPOMEOA BATATAS

From ontogeny of the tapetum in Ipomeoa batatas, the ultrastructural feature of tapetal cells are as follows, (l) At stage of the microspore mother cell, besids that the tapetal cytoplasm contains a large number of rough endoplasmic reticula, dictyosomes, ribosomes and mitochondria, the obvious feature is that electron-dense starch grains are accumulated. After meiosis of the microspore mother cells, starch grains resolved. The increase of the amount and volume of the lipid bodies within cytoplasm of the tapetal cells is accompanied by decomposition of the starch grains. This shows the formation of the lipid body is close related to the starch grain. (2) At stage of the meiosis: The cytoplasm of the tapetal cells contains a lot of vesicles-like structure formed by endoplasmic reticula and dictyosomes. The amount of the mitochondria increase prominently. Pro-Ubisch and sporopollenin bodies are forming by endoplasmic reticula, while pro-Ubisch body is forming by mitochondria.(3) Stage fcom microspore formation to bicellular pollen grain, besides that pro-Ubisch bodies are countiriucly forming by mitochondria, lipid bodies is decomposed into vesicles or small lipid bodies, then vesicles accumulated osmiophilic materials transform sporopollenin bodies and small lipid bodies accumulated osmiophilic materials transform pro-Ubisch bodies. The rapid increase of sporopollenin, pro-Ubisch bodies is accompanied by the degeneration of lipid bodies. This shows the formatien of sporopollenin pro-Ubisch bodies is close related to the lipid bodies. Expect lipid bodies and mitochondria, the organelles of the tapetal cells decomposed. (4) There is the peritapetal membrane at the inner tangential wall of tapetal cell.