鹤顶兰胚囊发育的超微结构观察

运用电子显微镜技术对鹤顶兰(Phaius tankervilliae(Aiton)BI.)胚囊发育过程中功能大孢子、二核胚囊、四核胚囊、成熟胚囊的超微结构进行观察,捕捉到了功能大孢子的三个阶段、成熟胚囊的两个阶段,进一步积累了鹤顶兰生殖生物学研究的基础资料.在功能大孢子、四核胚囊时期的合点端壁上可观察到胞间连丝,与体细胞间有物质及信息的交换,胚囊发育并非处于完全“隔离”状态.功能大孢子早期可见明显大液泡,随后进入第一次有丝分裂时大液泡消失,移向两极的染色体之间可见大量体积较小的液泡,成熟胚囊前期助细胞及卵细胞内也可见明显液泡,但当助细胞解体时,卵细胞内的大液泡也消失,液泡形态的变化可能是细胞生理状态发生改变的结果.

Ultrastructural Observation on Embryo Sac Development in Phaius tankervilliae（Aiton）Bl.

Embryo sac development in Phaius tankervilliae（Aiton）Bl. was observed under transmission electron microscope.Three phases of functional megaspore and two phases of mature embryo sac were captured in this study.At the functional megaspore and 4-nucleate embryo sac stages,plasmodesmata were present between nucellar cells and embryo sac at the chalazal end.Plasmodesmata are cellular communicating junctions that link adjacent cells to form symplast of a plant.They provide a direct channel for material transport and signal transduction,therefore megagametogenesis is not at an absolutely insulated situation.A big vacuole was observed at the early stage of functional megaspore before it disappeared during the first mitotic division.However,many small vacuoles appeared at the interspaces of separating chromosomes.Distinct vacuoles were also observed in the synergid cells and egg cell during the early stage of mature embryo sac,but vanished when synergid cells degenerated.The change of vacuoles probably resulted from the cell physiological change.Our results may provide insights into reproductive biology of Phaius tankervilliae.