Saccharina japonica( Aresch. )C. E. Lane,C. Mayes et G. W. Saunders( = Laminaria japonica Aresch. ) (Phaeophyta) is an important economic seaweed in China. There is a distinct outcome about the chromosome number in this kelp due to the tiny size of these chromosomes. The karyotypes and chromosomes of S. Japonica were observed after a series of treatments including pretreatment with 0. 2% colchicines for about 10 h, Carnoy' s fixative, and mixture of enzymes prior to dropping from 30 cm height overhead glass slides for spreading the surface coat. The prepared chromosomes were stained with 4',6-diamidino-2-phenylindole ( DAPI), a fluorescent probe sensitive and specific to DNA. The chromosome numbers of the haploid male and female gametophytes were 31 respectively,and there were 62 in diploid sporophytes. Most of the chromosomes were either droplet or short bacilliform. In the meantime, the female gametophyte chromosomes were between 0. 78 μm and 2. 61 μm in size, larger than the males that were between 0.57 |xm and 2.17 μm. Based upon the relative size of chromosome, the karyotypes of the female or male gametophyte chromosomes were primarily analyzed. All the results laid a solid foundation for a basic technique for localization of molecular markers on kelp chromosomes.%鉴于海带染色体比较小且数目存在分歧等原因,利用0.2％秋水仙素对海带配子体及孢子体处理10 h左右,经过卡诺试剂固定、多种酶组合处理及30 cm的高位滴片,可以获得质量比较高的海带染色体；使用灵敏度高、特异性强的DNA荧光染料DAPI进行染色,结果显示,海带雌、雄配子体的染色体各为31条,孢子体染色体为62条,大多为短杆状或者点状；雌配子体染色体的大小为0.78～2.61 μm,稍大于雄配子体(大小为0.57～2.17 μm).根据染色体的大小,对海带配子体的染色体核型进行了初步分析.这些结果为分子标记的染色体定位等细胞学研究奠定了技术基础.
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