含笑花药发育的超微结构研究

Ultrastructural Observation of the Microsporogenesis and Pollen Development in Michelia figo

对含笑花药发育中的超微结构变化进行观察,结果显示:(1)花粉发育中有三次液泡变化过程——第一次是小孢子母细胞在形成时内部出现了液泡,这可能与胼胝质壁的形成有关;第二次是在小孢子母细胞减数分裂之前,细胞内壁纤维素降解区域形成液泡,它的功能可能是消化原有的纤维素细胞壁;第三次是在小孢子液泡化时期,形成的大液泡将细胞核挤到边缘,产生极性。(2)含笑花粉在小孢子早期形成花粉外壁外层,花粉外壁内层在小孢子晚期形成,而花粉内壁是在二胞花粉早期形成;花粉成熟时,表面上沉积了绒毡层细胞的降解物而形成了花粉覆盖物。研究认为,含笑花粉原外壁的形成可能与母细胞胼胝质壁有关,而由绒毡层细胞提供的孢粉素物质按一定结构建成了花粉覆盖物。

The ultrustructural features of developing anthers of Michelia figo were studied using transmission electron microscope technique.The results are as following：（1）During pollen development,the vacuolization took place three times.The first time was the microspore mother cells （MMC） displayed evident vacuoles in the cytoplasm,which may relate with forming callose wall to separate the MMCs.Then the vacuoles appeared again in periplasm region of MMCs before its meiosis,which may relate with dissolving their cellulose wall.At the same time,many vacuoles appeared in the cytoplasm,increasing volume of cell and preparing for tetrad.The third time was the vacuolization which took place at late microspores.A big vacuole occupied most space of microspore,extruded its nucleus to periplasm,which created a polarity of microspore,preparing for asymmetric gametophytic division.（2）The sexine of exine of Michelia figo appeared first at the early microspore stage.The nexine of exine is synthesized at the late microspore.The intine of pollen grain was synthesized by vegetative cell of bicellular pollen.Finally,the degradating substance of tapetum cumulated on the surface of tectum of pollen grain to form the pollen coat.