洋葱珠孔塞的超微结构

洋葱（Ａｌｌｉｕｍ ｃｅｐａＬ．）珠孔塞由珠柄表皮细胞径向伸长特化而来，外观呈扇形规则地排列于珠孔之外。超微结构观察表明，珠孔塞细胞富含线粒体、粗顼内质网、高尔基体、核糖体等细胞器，细胞质内含大小不等的液泡。珠孔塞细胞朝外的分泌面有质膜内陷及不发达的壁内突，细胞壁外嗜锇分泌物较厚且呈明显的层次。在珠孔塞细胞、珠孔塞与珠柄细胞之间，有较多胞间连丝。

Ultrastructure of the Obturator in Allium cepa L.

The obturator of Allium cepa L. is specialized from epidermal cells of the funicle. The fan shaped funicle cells radially lengthened on longitudinal section and regularly arranged outside the micropyle. The ultrastructure showed that the obturator cells were rich in mitochondrion, rough endoplasmic reticulum, Golgi body and ribosome. The large or small vacuoles existed in cytoplasm. The plasma membrane invagination was observed on the outside secreting section of the obturator cells, and it rapidly formed non prosperous cell wall ingrowths. There were thicker secretions outside the cell walls, and they showed obvious layers. There are more plasmodesma among obturator cells and between the obturator and funicle cells.