白桦雄配子体的形成

Formation of the Male Gametophyte of Betula platyphylla

１９９６年以３０～３５年生白桦的雄性花序为材料，分期取样固定，利用ＯＬＹＭＰＵＳ显微镜进行观察。结果表明：６月底７月初出现小孢子母细胞，接着进入减数分裂过程。７月底８月初减数第一次分裂结束，随之减数第二次分裂开始，８月中旬分裂完毕，产生小孢子。从小孢子母细胞到产生小孢子历时约一个月左右。８月中旬之后便暂停发育，以单核小孢子越冬，次年４月末小孢子继续发育，经过一次或两次有丝分裂，于５月中旬形成成熟的雄配子体即花粉。白桦小孢子母细胞减数分裂过程中胞质分裂方式为同时型。四分体有三种存在形式。

The male catkins of 30～35-year-old Betula platyphylla were gathered and fixed by FAA fixation fluid in 1996 The meiosis of microspore mother cells and male gametophytes' formation were studied with OLYMPUS microscope. The results show that microspore mother cells form in the end of June or at the beginning of July, then the meiosis follows, the first phase of meiosis ends in the end of July and the second phase ends in the middle ten days of August, then the microspores form. This development takes about one month. At this moment, the development of microspores stops temporarily, and the microspores survive the winter. In April of the next year, the growth of microspores goes on, matured male gametophytes form in the middle ten days of May, which is the result of once or twice mitosises. The form of the cytokinesis of meiosis is simultaneous type. The quartets have three types.