棉花花粉水合和萌发时超微结构的变化：着重论述内质网和被膜小泡

棉花(Gossypium hirsutum L.)花粉在授粉后水合至萌发时期的营养细胞中贮藏的大量淀粉粒和脂体被动用。超微结构的观察表明,首先是造粉质体中的淀粉粒降解,尔后是脂体。在花粉水合至萌发时期,营养细胞中内质网和高尔基体十分活跃,并含丰富的被膜小泡。内质网的构型发生明显的变化:花粉刚水合时内质网潴泡高度扩张,不同程度扩张的内质网潴泡连续成网状并折迭形成许多囊袋状结构单位,其中包含造粉质体、脂体和被膜小泡群;其后,内质网潴泡形成的囊袋状结构消失,变为分支互通的网状结构;至萌发时,内质网潴泡略为扩张,有些连续成简单的网状,有些呈游离的囊泡状。被膜小泡始终是成群地分布,并与脂体联结,当脂体降解时一些被膜小泡与之融合。根据棉花花粉在水合至萌发时期,营养细胞质中存在独特形态的内质网系统和含丰富的被膜小泡,它们的动态行为及与淀粉和脂体的转化和降解之间的密切关系,讨论了这两种细胞器可能的功能。

ULTRASTRUCTURAL CHANGES IN HYDRATING AND GERMINATING POLLEN GRAIN OF COTTON,WITH SPECIAL REFERENCE TO ENDOPLASMIC RETICULUM AND COATED VESICLES

Numerous starch granules and lipid bodies stored in cotton ( Gossypium hirsutum L.) pollen grain are mobilized at the time from pollen hydration to germination after pollination. The ul-trastructural events during these processes were investigated. The starch granules were decomposed prior to the lipid bodies. From pollen hydration to germination, the rough endoplasmic reticulum (RER) and dictyosomes with functional activities were mainly involved in its vegetative cytoplasm, in which large number of coated vesicles were contained. The most conspicuous feature occurred in the vegetative cytoplasm was the remarkable consecutive changes in the configuration of RER. As the pollen just hydrated, the RER cisternae became highly distended in various degree to form a net-work system and were further folded into large amount of RER pocket-like units, containing amyloplasts, lipid bodies and groups of coated vesicles. As the pollen continued to hydrate, the previously formed ER pockets disappeared and the ER cisternae were linked together to form a branched communicat- ing system. When the pollen started to germinate, the ER cisternae became slightly dilated. Some of them were associated with each other to form a simple net-work system,and others remained as free vesicles. During the whole process, the coated vesicles, which always distributed in groups, were linked closely with the lipid bodies. As the lipid bodies decomposed, some of the coated vesicles lost their membranes and coalesced with the decomposed lipid bodies. Based on the close relationship between the dynamic changes of the pollen ultrastructures and the stages for pollen hydration to the initiation of germinate, the possible functions of the ER and coated vesicles are discussed.