Fertilization in Brassica campestris ssp. pekinensis and its duration of each stage

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 before 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 before mitotic division of the primary endosperm nucleus. (12) 24 h after pollination, the division of the primary endosperm nucleus actually takes place. __________ Translated from Acta Horticulturae Sinica, 2005, 32(5): 812–817 [译自: 园艺学报]