朱顶红生殖细胞分裂过程中微管超微结构的变化

用透射电镜的方法，对朱顶红（Ａｍ ａｒｙｌｌｉｓｖｉｔｔａｔａ Ａｉｔ．）花粉管中生殖细胞的分裂过程中微管分布和结构形态变化进行了观察，获得如下主要的结果：有丝分裂前期，微管的数量较分裂前减少并变短，靠近细胞核分布。分裂前中期，微管出现于原来的核区并与染色体发生联系，形成着丝点微管。分裂中期，染色体排列于赤道面上形成赤道板，微管构成纺锤体。分裂后期，染色体分成两群，被缩短的着丝点微管拉向两极。在纺锤体两极的微管汇聚。后期的晚期，当极的微管尚未消失时，在赤道区域出现丰富的成膜体微管，在成膜体中央，细胞板前体物聚集。分裂末期，极微管和着丝点微管消失，成膜体微管在新形成的核膜和细胞板间扩展并穿过细胞板

ULTRASTRUCTURAL CHANGES OF THE MICROTUBULE IN THE GENERATIVE CELL OF AMARYLLIS VITTATA AIT. DURING MITOSIS

Structural changes of microtubules (MTs) in the generative cell (GC) of Amaryllis vittata Ait. during mitosis in pollen tube have been investigated with electron microscopy. The division cycle was completed approximately within 12 h. During prophase, the MTs bundles distributed in the cortex of the GC, they were less and shorter than that before mitosis, some of which beginning to be near the nucleus. When the chromatin condensed and the GC entered metaphase, the MTs increased in number and distributed among the chromosomes (CHs) in the original nuclear zone, but they were not arranged in distinct bundlesed.Some of them connected with the CHs to form kinetochore MTs (KMTs), where as the cortical MTs in prophase still remained there. During metaphase, the CHs were arranged on the equartor forming a metaphase plate, and all the MTs formed a diffuse spindle. When the GC entered anaphase, the KMTs were shortened and they were involved in the segregation of the CHs into two groups.The MTs were much more and focused in the two polar regions. In late anaphase, while the MTs still existed at the poles, rich phragmoplast MTs appeared in the equator zone and the precusors of cell plate (CP) aggregated in the middle of the phragmoplast. When the GC entered telophase, the CHs diffused as chromatin, and phragmoplast MTs extended between the two newly formed nuclear envelops and even through the CP while the polar MTs and KMTs disappeared, the MTs in the newly formed sperm cells were different from that of the GC.