大白菜的胚胎发育

EMERYO DEVELOPMENT OF BRASSlCA CAMPESTRIS SSP. PEKlNENSlS

大白菜(Brassica campestris ssp.pekinensis)合子伸长后,经不均等分裂而形成二细胞原胚,进而形成三细胞和四细胞原胚以及四分体和八分体原胚。接着进入原胚后期。原胚发育属柳叶菜型荠菜变型。再经过渡期、心形期,鱼雷形期、手杖形期和马蹄形期,以至成熟。同时,还描述了各发育阶段的特点和各主要组织、器官的发生来源,讨论了原胚的划分和胚胎发育规律等问题。

The zygote of Brasiica campestris ssp. pekinensis elongates considerably before its first unequal transverse division forming a 2-celled proembryo. Another two divisions give rise to the 3- and 4-celled proembryos, which is followed by still another two divisions forming the quadrant and octant stages. After that, late proembryo develop- ment starts. Proembryo development is of the Capsella-variation of Onagrad type. A series of development stages such as the transitional, the heart-forming, the torpedo-liked, the walking stick-liked and the horseshoe stages can be distinguished during embryo maturation. The structural features of all the development stages and the morphogenesis of the main tissues and organs in the embryo are given a ditailed descreption. The determination of the proembryo stage and the regularities of embryo development are also presented.