The Ultrastructural changes of female gametophyte during its development in the apomictic monosomic addition line M14 of beta corolliflora in sugar beet | 甜菜无融合生殖单体附加系M14雌配子体发育的超微结构观察

Chino. 【目的】阐明甜菜无融合生殖单体附加系M14雌配子体发育的超微结构特征。【方法】以甜菜无融合生殖单体附加系M14（Beta vulgaris L. VV+1C、2n=18+1）为实验材料,利用电子显微镜技术对其雌配子体的发育过程进行研究。【结果】甜菜无融合生殖单体附加系M14为兼性无融合生殖体,二倍体孢子生殖为蝶须型（Antennaria-type）和韭型（Allium odorum-type）,有性生殖为蓼型（Polygonum-type）。蝶须型为主要发育方式,超微结构特征为：雌配子体发育速度较快,从功能大孢子直到细胞化雌配子体时期,细胞器的种类与数量呈现增长趋势：细胞核核仁较大,存在核仁泡,核孔明显;核糖体数量多;线粒体的数量一直较多,从二核雌配子体出现内嵴,膜的结构变得清晰,八核雌配子体的线粒体基质呈电子透明状,细胞化后期恢复到原来的状态;质体的数量变化不大,形状多样,有的含淀粉粒;内质网呈分枝的管状或交织成索状分布在细胞核、液泡或细胞壁附近;高尔基体的数量相对较少,但在未退化的助细胞中十分丰富,活跃地分泌小泡;脂滴一直都存在,常与液泡及线粒体相互靠近;细胞化后期,绝大多数雌配子体的助细胞先后退化,极少数雌配子体只有一个助细胞退化,另一个宿存。韭型与蓼型雌配子体发育速度较慢,与蝶须型相比,直到单核雌配子体时期未见细胞器种类与数量发生明显变化。蝶须型与韭型、蓼型雌配子体仅在功能大孢子与单核胚囊时期通过是否有胼胝质壁加厚以及珠孔端有无退化的细胞痕迹进行区分。【结论】蝶须型、韭型、蓼型雌配子体发育过程中的超微结构特征差异明显,蝶须型雌配子体从功能大孢子至细胞化时期,雌配子体体积增大,细胞器的种类与数量随之增加,呈现代谢旺盛状态。推测蝶须型雌配子体在其后的发育中占优势。单核雌配子体之前依据珠孔端是否有退化细胞痕迹以及有无胼胝质壁加厚可将蝶须型与韭型、蓼型从结构上予以区分。韭型、蓼型从功能大孢子至单核雌配子体时期,雌配子体的体积以及细胞质的成熟程度均呈缓慢增长趋势。推测在其后的发育过程中大量退化。

Inglés. 【Objective】This study explored the ultrastructural changes of female gametophyte during its development in the apomictic monosomic addition line M14 of Beta corolliflora in sugar beet. 【Method】 The ultrastructural changes were investigated by electron microscopy. 【Result】 The monosomic addition line M14 is a facultative apomict. The diplosporous female gametophytes are of Antennaria type and Allium odorum type sexuality is of Polygonum type. Antennaria type is the main one and its ultrastructural characteristics are that the development of female gametophyte was rapid, from the functional megaspore until the cellularized embryo sac, the category and amounts of organelles present the following growth trend, i.e. nucleolus which are more big had nucleolus vacuoles, nuclear pores are obvious; there are many ribosome; also a lot of mitochondria in the development of female gametophyte, many tubes appear from the two-nucleate embryo sac, but transform into electron-transparent in eight-nucleate embryo sac, then recovered as former. The number of plastids was stable and their shapes were varied, some of them contained starch grains. The endoplasmic reticulum had many branches or were interwove as ropes near nucleus, vacuoles and cell walls. Dictyosomes were relatively rare in the development of female gametophyte, but abundant dictyosome which often associated with many small electron-transparent vesicles was found in the persistent synergid. Some lipid drops were always present near the vacuoles and mitochondrias. Late period of cellularized megagametophyte, two synergids successively degenerated in the great majority of embryo sacs, very few had only one degenerated synergid, with another persistent. Compared with Antennaria type embryo sac, the development of Allium odorum type and Polygonum type were slowly, there were no obvious changes of category and amounts of organelles until the period of one-nucleate embryo sac. Whether had degenerated cell and deposition of callose during the development of functional megaspores and one-nucleate embryo sacs were the characters distinguishing the Antennaria-type gametophyte of female and Allium odorum-type.【Conclusion】 There were distinct characteristics during the development of Antennaria-type, Allium odorum type and Polygonum type gametophyte. From the functional megaspore until the cellularized embryo sac, Antennaria type gametophyte present high rate of metabolic activity, its volume augmented increased with category and amount of organelles. It is supposed that Antennaria type gametophyte dominated the afterward growth. Whether had degenerated cell and deposition of calluses before the development of one-nucleate embryo sacs were the characters distinguishing the female gametophyte of Polygonum type, Antennaria type or Allium odorum type. From functional megaspores to one-nucleate embryo sacs, volume and cytoplasmic mature degree of Allium odorum type and Antennaria type embryo sac present slow-moving growth trend. It is concluded that most sexual female gametophyte degenerated in later developmental stages.