摘要
应用电子显微镜观察了朱顶红(Amaryllis uittata Ait.)萌发花粉粒和花粉管中的生殖细胞微管的结构和分布。在开始萌发的花粉粒中,生殖细胞呈长卵圆形,被本身的质膜及营养细胞的内质膜所包围。两层质膜波浪起伏状,细胞表面弯曲不平。在横切面上,生殖细胞略圆形和有许多隆起。生殖细胞的微管系统主要组成束,但也有单个的微管。微管的束一般位于细胞周缘的隆起处和靠近质膜。微管束排列的取向与细胞的纵轴平行。一束微管至少集聚有5—6个微管,大多数有约30个。在束中的微管之间有的可见“横桥”联结。单一的微管散布于细胞质各处和有不同的取向。当花粉管生长时,转移至花粉管中的生殖细胞变为长形,在细胞的前端和后端细胞质扩展。在此的期生殖细胞中微管的结构形式与萌发的花粉粒中的相似。不过,在一束的微管中含微管的数目增多,一般有50—60个,束中徽管之间的“横桥”连结着3—5微管仍然是清楚的。在花粉管中,生殖细胞与营养核之间发生位置的交换,有些超微结构的图形揭示了生殖细胞与营养核之间存在物理的联结,可以看到生殖细胞前端不规则的细胞质延伸被包藏在营养核中,以及细胞质的突起伸入营养核深的内陷中。在切面上生殖细胞的外突或扩展的细胞质部分可见许多的微管片断。本研究征明:微管在维持生殖细胞特殊的形状和在生殖细胞与营养核之间维持紧密的联结上起重要的作用,而且也可能对生殖细胞在花粉管中的运动起一定的作用。
The organization of microtubules (MTs) in the generative cell (GC) of germinated pollen and pollen tube in Amaryllis vittata Ait. has been studied with electron microscopy. At the begin- ning of pollen germination,the GC is long elliptic in shape,and is surrounded by its own mem- brane and also by that of the vegetative cell (VC),both of which appear undulated. In cross sec- tion,the GC appears roundish and has many lobes. The MT system of GC is mainly organized in bundles, but single MTs can also be observed. The MT bundles are generally located in the lobes, directly beneath the plasma membrane of the cell. These MT bundles orientate along the longitudi- nal axis of the cell. They are formed by aggregation of 5--6 MTs at least,more often about 30 MTs. In the bundles the MTs are often linked to each other by 'cross-bridge'. The single tubules in the cytoplasm distribute randomly in different orientations. When the GC has migrated into the pollen tube after germination,it becomes elongated and has cytoplasmic extensions both in the an- terior and posterior end of the cell. The organization of MTs of the GC in pollen tube is similar to that in the germinated pollen grain, but the number of MTs in a bundle often increases to 50-- 60. In the bundle the 'cross-bridges' between the MTs which always link 3--5 MTs, are still seen clearly. Positional shift between the GC and Vegetative nucleus (VN) may take place during the growth of pollen tube. The physical association between GC and VN may be demonstrated some ultrastructural figures. It may be seen that irregular cytoplasmic extensions in the anterior end of the GC is always enclosed by the VN and the projections of the cytoplasmic extensions lie within enclaves of the VN. There are many MTs sheets in the lobes or extensions in the cytoplasm of the GC. Thus the present study demonstrates that MTs have an important role in maintaining the peculiar shape of the GC and the close association between GC and VN. However, it seems that the MTs are probably also engaged in the movement of the GC during pollen growth.
基金
国家自然科学基金
高等学校博士学科点专项科研基金
关键词
朱顶红
生殖细胞
微管
超微结构
Amaryllis vittata
Generative cell
Microtubule
Ultrastructure
