洋葱胚珠和双受精的观察

Ovule and Double Fertilization in Allium cepa L.

洋葱胚珠具两层珠被,为薄珠心。在雌配子体发育过程中珠心细胞解体消失,成熟胚囊直接与内珠被邻接。胚珠外由珠柄表层细胞特化为珠孔塞,反足细胞很早消失。但在胚囊的合点端形成不大的珠心柱,推测它有助于营养物质向胚囊转运。二个助细胞中无大液泡,结构较特殊,且大小不等,可能具有不同功能,配子融合属于有丝分裂前的受精类型。

The ovule of Allium cepa L. is bitegmic and tenuinucellate. the peri-pheral nucellar cells degenerated during female gametophyte development.So the mature embryo sac directly contacts inner integument. The epidermalcells of funiculus differentiated into obturator near the micropyle. Three antipodal cells are ephemeral. In the chalazal end of ES, a smallpostament formed, which probably plays some role in the transportationof nutrient to the ES. Two synergids are not equal in size, special instructure and may have different functions. The fertilization of onion belongs to premitotic type of syngamy.