甜菜无融合生殖单体附加系M14花粉发生与发育的超微结构研究

Microsporogenesis and Pollen Development in Apomitic Monosomic Addition Line M14 of Beta corolliflora in Sugar Beet

运用透射电子显微镜技术,对甜菜无融合生殖单体附加系M14的小孢子发生、雄配子体发育以及相应的花药壁发育过程进行超微结构的观察研究,以阐明甜菜无融合生殖单体附加系M14花粉发生与发育超微结构特点以及花粉败育的时期和败育的细胞学特征.结果显示:(1)小孢子母细胞减数分裂正常,分裂期间细胞质具有明显的细胞质改组"现象,主要表现在核糖体减少,质体、线粒体的结构发生规律性的变化,有利于孢子体向配子体的转变.M14减数分裂的胞质分裂为同时型,前期Ⅱ和中期Ⅱ形成细胞器带";正常发育的花粉,小孢子分裂形成营养细胞和生殖细胞;生殖细胞脱离花粉壁,生殖细胞游离于营养细胞的细胞质中,最初具细胞壁,而后消失,且生殖细胞壁成分与花粉内壁成分相似.(2)三细胞型的成熟花粉含有一个营养细胞和两个具有尾突的精子;每个精子通过两层质膜与营养细胞隔开,含有一个大的精核,长尾突内含少量的细胞质以及纤丝状结构.(3)生殖细胞和精子中缺乏质体.(4)花粉的败育起始于小孢子,大部分受阻于单核-二细胞花粉期,其败育特征为花粉内液泡吞噬作用导致细胞器解体,绒毡层细胞过早解体或肥大生长致使营养供应受阻,可能是导致单核-二细胞花粉败育的主要细胞学原因.研究表明,白花甜菜第九号染色体的附加可能是导致M14大量花粉败育的遗传学因素.

The ultrastructures of male gametophyte, microspores and pollen wall were studied by electron microscopy in order to show the characteristics of microsporogenesis, abortive stage and abortion in apomitic monosomic addition line M14 of Beta corolliflora. The results were as follows： （1）Meiosis of microspore mother cell was normal. Obvious ＂cytoplasm reorganization＂ was observed during meiosis in the cytoplasm, which mainly presented in the decrease of ribosome and regular changes of plastid and mitochondria. This phenomenon appeared to facilitate the transfer from sporophyte to gametophyte. Organelle band occurred at the stage of Prophase Ⅱ and Metaphase Ⅱ ,as cytokinesis belongs to simultaneous type. Microspore mitosis form generative and vegetative cells. The generative cell wall whose component was similar with intine detached from the intine and immersed in the cytoplasm of vegetative cell. The cell wall around generative cell disappeared later. （2）There were two sperms with long caudals and one vegetative nucleus in mature trinucleus pollen grains. Each sperm was separated from vegetative cell by two membranes which enclose its big nucleus. The long caudal has few cytoplasm and fiber structure. （3）There was no plastid in generative cell and sperms. （4）The abortion initial stage was microspore, most disruption occurred in monokaryotic microspore and 2-celled pollen. Abortion is characterized by the organelles＇ degradation lead by phagocytosis of vacuole; premature degradation or hypertrophy growth of tapetum leading to disruption of nutrition supply may be the main cytological reasons of monokaryotic microspore and 2-celled pollen abortion. While the additional chromosome No. 9 of Beta corolliflora Zoss may be the genetic factor of aboundant pollen abortion.