Abstract: To understand the degeneration of unfertilized aposporous embryo sac in an aposporous species Pennisetum squamulatum, the central cell in the unfertilized embryo sac was characterized ultrastructurally . The most prominent sign of degeneration is that the central cell nucleus produced nuclear vacuoles . These nuclear vacuoles can be classified into singleand
double- layered types . Single- layered nuclear vacuoles are found in the cytoplasm, while the double-layered are inside the nucleus . There are two ways to produce nuclear vacuoles . One is that the outer membrane of the nuclear envelope distends towards the cytoplasm to form nuclear vacuoles ; and the other is the double-layered nuclear envelope derives vacuoles by depressing inwards . Nuclear envelope types are in relation to the ways they are produced . All nuclear vacuoles absorb cytoplasm or nuclear matrix , and trap organelles such as mitochondria .

Key words: Embryo sac degeneration

摘要： 为理解植物无孢子生殖胚囊未受精条件下的退化, 对无孢子生殖植物非洲狼尾草未受精成熟胚囊中央细胞退化做了细胞形态学研究。没有受精的中央细胞退化时最显著的特点是细胞核产生核膜囊泡。核膜囊泡有两种类型: 单层膜的囊泡和双层膜的囊泡, 单层膜囊泡在细胞质中, 双层膜囊泡在细胞核内。核膜囊泡有两种发生方式: 1) 核膜的外膜向细胞质一侧膨胀产生囊泡, 囊泡进入细胞质; 2) 核膜向核内凹陷形成囊泡, 囊泡进入细胞核。核膜囊泡类型与产生方式密切关联。核膜囊泡吞噬并消化包括线粒体在内的细胞质和核质。

关键词: 胚囊退化, 核膜囊泡, 非洲狼尾草, 未受精无孢子生殖胚囊FONT