西瓜绒毡层细胞退化超微结构研究

Ultrastructural study on the tapetal cell degeneration in watermelon

为研究西瓜绒毡层退化的结构特点,尤其是绒毡层的退化与花粉发育的关系,用光学和电子显微镜研究了西瓜绒毡层退化过程。结果表明,绒毡层有P-绒毡层细胞和C-绒毡层细胞2种类型,它们一前一后分批死亡。当花药发育到游离小孢子时期,P-绒毡层细胞发生凝缩,呈现退化特征;相反,C-绒毡层细胞则体积增大,直到花粉发育为成熟雄配子体时期才完全退化解体。膨胀的C-绒毡层细胞中,内质网先发生聚集,之后断裂并产生大量内质网小泡;随着内质网小泡内容物增浓,细胞质逐渐变稀;最后,细胞内容物几乎全部变成多糖颗粒和以脂类物质为主的滴状物。细胞解体后,多糖颗粒和脂滴移向花粉粒,其中脂滴黏附在花粉壁表面或镶嵌在外壁空隙中形成花粉鞘。绒毡层细胞以严格程序分批退化,保证了绒毡层向花粉提供养料的延续性,使得绒毡层退化与花粉发育2种相反的过程协同完成。

In order to study the structure of tapetal degeneration in watermelon （Citrullus lanatus）, especially on the relationship between the tapetal degeneration and pollen development, the light and electron microscopes were used. Results showed that tapetum in watermelon contained two groups of cells, Ptapetal and C-tapetal cell types, which degenerated and died at different stages. P-tapetal cells degenerated by shrinking when pollen development was in free microspore stage. However, at the same time, C-tapetal cells began to enlarge. Endoplasrnic reticula in enlarged C-tapetal cells were aggregated in stacks at first, and then produced numerous ER-vesicles. As inclusions in the vesicles increased, the cytoplasm in these cells deereased until it was replaced by starch grains and lipid droplets. These stareh grains and lipid droplets moved to pollen grains. Lipid droplets were attached to pollen surface or trapped in cavities in pollen exine, to form pollenkitt. Occurrence of P- and C-tapetal cells is supposed to ensure sustainable supply with nutrients to pollen grains, and therefore contribute to eooperarive complement of tapetal degeneration and pollen development.