杜仲花粉不对称分裂的超微结构观察

The Ultrastructural Observation on the Asymmetric Division of Eucommia ulmoides

运用透射电镜对杜仲花粉发育进程进行了观察研究。结果显示,杜仲小孢子的第一次分裂为不等分裂,形成小的生殖细胞和大的营养细胞。分裂开始前小孢子的营养极形成许多小液泡,建立细胞极性;然后随着核膜的解体核周围的细胞器逐渐向纺锤体区靠近,围绕在纺锤体周围。花粉第一次有丝分裂完成后,生殖细胞所获得的细胞器开始分布在细胞的两侧,后来移向生殖细胞的营养极,而紧贴花粉壁的生殖极无细胞器分布。这种生殖细胞早期的细胞极性,可能为进一步分裂形成精细胞奠定基础。

Eucommia ulmoides microspore produces two different daughter cells by asymmetric division which is respectively the large vegetative cell and the small generative cell. A few small vacuoles are pres- ented in the position of future vegetative pole before the asymmetric division,then the cellular polarity is established. Accompanying with the karyotheca breaks up ,the organelles surrounding the nuclear move to the area of the spindle and enclose it later. When PMI finishes, the organelles distributed into the generative cell disperse in both sides of the cell initially,afterward they migrate to the area near the vegetative pole. There are no organelles in generative pole of generative cell near pollen wall. It was hypothesized that the early polarity in the generative cell may lay foundation for the subsequent pollen mitosis to form sperms.