八种国产大戟属植物的核型报道

Karyotypes of eight species of Euphorbia L. (Euphorbiaceae) from China

８种大戟属ＥｕｐｈｏｒｂｉａＬ．植物的核型分析结果表明，大戟属不同亚属的染色体基数与其形态变异的复杂性有一定关系。地锦草亚属ｓｕｂｇｅｎ．Ｃｈａｍａｅｓｙｃｅ３个种染色体基数分别为ｘ＝８，９，１１；一品红亚属ｓｕｂｇｅｎ．Ｐｏｉｎｓｅｔｉａ两个种染色体基数均为ｘ＝７，分别为四倍体和八倍体；乳浆大戟亚属ｓｕｂｇｅｎ．Ｅｓｕｌａ３个种，染色体基数分别为ｘ＝７，１０，１０。根据以前学者发表的资料分析，一品红亚属和大戟亚属ｓｕｂｇｅｎ．Ｅｕｐｈｏｒｂｉａ的染色体基数是很稳定的，分别为ｘ＝７和ｘ＝１０；通奶草Ｅ．ｈｙｐｅｒｉｃｉｆｏｌｉａ为ｘ＝８的四倍体，它不仅有染色体整倍性的变异，还有异基数性的变化。结合以前学者的研究，笔者支持ｘ＝１０为大戟属的最原始基数的观点。齿裂大戟Ｅ．ｄｅｎｔａｔａ和通奶草具不同的染色体倍性，猫眼草Ｅ．ｅｓｕｌａ的细胞染色体数目观察证实了我国存在四倍体的居群，与欧洲和北美的植物构成一个典型的多倍体复合体。

In this paper,eight species of the genus Euphorbia L. were cytologically studied. The three species of the subgenus Chamaesyce Raf., E. hirta, E. humifusa and E. hypericifolia, had chromosome numbers of 2n=18,22 and 32, with their basic chromosome numbers being x=9,11 and 8 respectively. The two species of the subgenus Poinsettia(Grah.) House. E. dentata, with 2n=28, a tetraploid, and E. cyathophora, with 2n=56, a octoploid, had both the basic chromosome number of x=7. The three species of the subgenus Esula Pers, E. lathyris, E. helioscopia and E. hylonoma, had chromosome number of 2n=20,42 and 20, with their basic numbers being x=10,7 and 10 respectively. The basic chromosome number of x=8 is new for E. hypericifolia, in which x=7 was previously reported. This indicates that this species had both ploidy(2n=4x=28, 8x=56) and dysploidy(x=7,8) variations. In E. dentata, there occurred also ploidy variation (2n=2x, 4x and 8x). A tetraploid cytotype of E. esula was found in China, its diploid cytotype and hexaploid cytotype being previously reported in North America, the Iberian Peninsula and some other European areas. Based on our results and those previously reported, we support the viewpoint that x=10 may be the original basic chromosome number of Euphorbia and discuss the role of polyploidy and dysploidy in the speciation and evolution of this genus.