鹤顶兰珠心细胞程序性死亡的超微结构研究

Ultrastructural Observations of Programmed Cell Death of the Nucellar Cells in Phaius tankervilliae(Aiton) Bl.

应用电子显微镜对鹤顶兰(Phaius tankervilliae(Aiton)Bl.)珠心细胞进行了观察,结果发现,珠心细胞程序死亡(programmed cell death,PCD)过程中伴随着液泡破裂、染色质凝聚、细胞质解体等明显特征。在鹤顶兰功能大孢子形成之前,大孢子母细胞的侧细胞壁存在明显的内突。随着胚囊体积的逐渐增大,衰退珠心细胞残留的细胞壁叠合在一起,从而使胚囊壁不断加厚。胚囊成熟前,合点端珠心细胞与胚囊之间有胞间连丝相连。合点端珠心细胞的细胞质状态,特别是液泡形态与大孢子母细胞、功能大孢子、成熟胚囊时期的细胞状态高度相似。结果表明,衰退的珠心细胞不仅为胚囊的扩大提供空间,同时也为胚囊的发育提供营养,合点端珠心细胞对胚囊发育内环境的稳定性起着重要的屏障作用。

Nucellar cells in Phaius tankervilliae（Aiton） Bl.were observed under transmission electron microscope.Some distinct characteristics were found during the programmed cell death（PCD） of nucellar cells in P.tankervilliae,such as the vacuole splinter,demonstrating the chromatin condensation and cytoplasm disorganization.Many protuberances were present at the megasporocyte cell wall adjacent to the lateral nucellar cells before the formation of the functional megaspore.With the enlargement of the embryo sac,the thickening embryo wall became visible due to the superposition of the vestigial nucellar cell wall.Before maturation of embryo sac,the plasmodesmata connected nucellar cells and embryo sac at the chalazal end.The state of chalazal nucellar cell cytoplasm,especially the morphology of vacuole,was highly similar to that of megasporocyte cell,the functional megaspore and mature embryo sac.The results showed that nucellar cells played important roles in embryo sac development,and PCD of nucellar cells offers space and nutrition to the enlarged embryo.At the same time,the nucellar cell at the chalaza end make a stable interior condition for embryo sac development.