Abstract: Ultrastructural changes of the megasporogenesis of Triticum aestivum L were studied. During the meiotic process of megasporocyte, the ribosome population diminished greatly in prophase I and restored in metaphase I; plastids and mitochondria turned unclear (dedifferentiation) in prophase I and recovered their normal structures (redifferentiation) in metaphase I. All these proved that cytoplasmic reorganization took place during the megasporogenesis of Triticum aestivum. It was also found that the nuclear envelope disappeared earlier at the micropylar end than that at the chalazal end. The speed of the programmed cell death were different in three nonfunctional megaspores at the micropylar end and their relationships with the neighboring cells were also different. The biological significance was discussed about these phenomenon.

Key words: Triticum aestivum, megasporocyte, meiosis, cytoplasmic reorganization

摘要： 以小麦(Triticum aestivum L.)为材料研究了小麦大孢子形成过程中的超微结构变化。发现了小麦大孢子母细胞减数分裂过程中，核糖体密度在前期Ⅰ显著降低，到中期Ⅰ才完全恢复；质体和线粒体也出现了脱分化和再分化。从而证明了小麦的大孢子形成过程中也存在着细胞质改组现象。还发现了大孢子母细胞合点端的核膜先于珠孔端的消失，并且珠孔端3个大孢子的死亡时间不同，与相邻细胞的关系也不同，进而讨论了这些现象的生物学意义。

关键词: 小麦, 大孢子母细胞, 减数分裂, 细胞质改组