论文部分内容阅读
This paper reports the process of fertilization in Brassica campestris ssp.pekinensis and the duration of each stage.The results are as follows:(1)Pollen germinates on stigma 2-3 h after pollination.(2)4-8 h after pollination,pollen tube grows in the style.(3)8-14 h after pollination,pollen tube grows in the ovary and gets into the ovule via the micropyle.(4)16 h after pollination,one sperm nucleus moves to the egg and enters it.(5)The sperm nucleus adheres to the nuclear membrane of the egg 18 h after pollination.(6)20 h after pollination,it enters the egg nucleus and male chromatin gradually disperses and 24 h after pollination,a male nucleolus appears.A large female nucleolus and a small male nucleolus occur in the nucleus of the fertilized egg,and zygote formed.The dispersing of sperm chromatin in the egg nucleus takes about 4 h.(7)32--34 h after pollination,the division of zygote begins.The dormancy stage of the zygote lasts for about 8-10 h.(8)The pair polar nuclei lie in the chalazal end of the egg betbre fertilization,which may fuse into a secondary nucleus or not.(9)16-18 h after pollination,the sperm nucleus moves to the polar nuclei or the secondary nucleus.18 h after pollination,the sperm nucleus adheres to the nuclear membrane of the polar nuclei or that of the secondary nucleus.(10)20 h after pollination,the sperm nucleus enters one of the polar nuclei or the secondary nucleus and a triple fusion takes place.The process of fusion is similar to the karyogamy but faster.The dispersing of the sperm chromatin in the polar nucleus or secondary nucleus takes about 2 h.(11)22 h after pollination,the primary endosperm nucleus formed.The female and male nucleoli cannot fuse with each other betbre mitotic division of the primary endosperm nucleus.(12)24 h after pollination,the division of the primary endosperm nucleus actually takes place.