蒙古黄芪的胚胎学

EMBRYOLOGY OF ASTRAGALUS MONGHOLICUS BGE.

蒙古黄芪(Astragaius monghocus Bge.)雄性原为花药表皮下单列细胞,小孢子四分体为四面体型,胞质分裂为同时型。单子叶型花药壁。分泌型绒毡层,其细胞核始终一个,细胞里含有一至多个草酸钙晶体。二细胞型花粉:单室子房,多胚珠,弯生,双珠被,厚珠心。蓼型胚囊。雌性孢原为珠心亚表皮下多细胞。直线形大孢子四分体,合点端第一、或第二、或第三个大孢子有功能。成熟胚囊具有盲囊结构;花粉管通过退化助细胞进入胚囊。双受精属于有丝分裂前配子融合类型;胚的发育为柳叶菜型。核型胚乳。胚乳细胞在球形胚时期开始形成。在胚乳发育过程中,合点端胚乳游离核存在着聚集、合并、无丝分裂和胚乳细胞内多核合并等现象。

This paper describes the microsporogenesis and development of the male gametophyte,me- gasporogenesis and development of the female gametophyte,the double fertilization and de- velopment of the embryo and endosperm in Astragalus mongholicus Bge.,the main results are as follows:1.The male archesporium differentiates from a series of cells under the epidermis of the anther.The microspore tetrads are tetrahedial and the cytokinesis of the microspore mo- ther cells in meiosis is the simultaneous type.The development of anther walls conforms to the monocotyledonous type.The tapetum,of which each cell contains one or many calcium oxalate crystals and always remains uninucellate,is the secretory type.The mature pollen grain is the two-celled type.2.It is of uniovary and of multiovule being bitegeminous,crassinucellate and campylotropous,and the development of the embryo sac conforms to the Polygonum type. The female archesporium differentiates from many cells under the subhypodermis of nucellus. The four megaspores that the first one,or the second one,or the third one towards the chala- zal end is functional arrange in a line.The mature embryo sac has a caecum structure.3. The pollen tube enters into embryo sac through a degenerated synergid.The double fertiliza- tion belongs to the premitotic type of syngamy.4.The development of the embryo belongs to the Onagrad type and the development of the endosperm belongs to the nuclear type.The endosperm cells start to form during the stage of the globular proembryo.The phenomenon of free nuclei gathering and fusing in the end of the embryo sac,amitosis of free nuclei and fusing of many nuclei in anendosperm cell have been seen during the development of the en- dosperm.