摘要
用光镜和透射电镜观察研究了棉花(Gossypium hirsutum)和小叶杨(Populussimonii)小孢子母细胞中超数核仁的发生和动态变化过程。超数核仁出现于减数分裂前(棉花)和减数分裂前期Ⅰ早期(小叶杨),产生部位是核仁组织者区域。超数核仁与主核仁有类似的染色特性,但体积小,数量丰富。在小孢子母细胞减数分裂过程中,超数核仁通过下述主要方式进入细胞质:一是在分裂中期和后期核膜暂时解体时进入细胞质中;另一是在核膜完整时通过状态的变化经核膜孔进入细胞质或以整体形式通过核膜外突并缢出进入细胞质中。小孢子母细胞中超数核仁的发生可能是大量迅速补给细胞质核糖体数量的一种机制,与孢子体转向配子体的发育有关。
The origin and movement of supernumerary nucleoli in the microsporocytes of both Gossypium hirsutum and Populus simonii are examined with optical and electronic microscopy.Supernu- merary nucleoli are supposed to be formed at the nucleolus organising region(NOR)of nucleolar chromo- somes before meiosis in the meiocyte of Gossypium hirsutum and during lepotene/pachytene in the meiocyte of Populus simonii,they are released from NOR to become distributed throughout the karyoplasm later. Supernumerary nucleoli are rich in number,small in size,and have similar stain characteristics as the par- ent cell nucleoli.During meiosis,the supernumerary nucleoli eventually appear as the cytoplasmic nucle- oloids after moving into cytoplasm in the following possible ways:first,supernumerary nucleoli are re- leaesd into cytoplasm at metaphase Ⅰ/anaphase Ⅰ and metaphaseⅡ/anaphase Ⅱ when the nuclear en- velopes are in the state of breakdown;Secondly,supernumerary nucleoli may get into cytoplasm by exocy- tosis across nuclear envelope or by changing into small units and further get into cytoplasm through nucle- ar envelope pores when the nuclear envelopes are in intact state.The formation of numerous supernumer- ary nucleoli and their active transport into cytoplasm in the meiocytes are considered to be linked with the rapid buildup of ribosome number,and these processes probably are related to the transition from sporo- phytic to gametophytic generation.
基金
北京中关村分析测试基金资助
关键词
棉花
小叶场
超数核仁
减数分裂
Gossypium hirsutum
Populus simonii
microsporocyte
meiosis
supernumerary nucleolus
