长柄山蚂蝗属三个种的核型分析及山蚂蝗属两个种的染色体数

长柄山蚂蝗属Podocarpium(Benth.)Yang et Huang属蝶形花科,间断分布于东亚和中北美洲,广布种分布到非洲和大洋洲。北美有4种,亚洲约有14种.我国约有该属植物11种,以西南和长江以南地区分布种类最多。国外已有人做过本属一半以上的种的染色体记数和核型。本文对本属的三个种.长柄山蚂蝗P.podocarpum(DC.)Yang et Huang,大苞长柄山蚂蝗P.williamsii(Pamp.)Yang et Huang和云南长柄山吗蝗P.du-clouxii(Pamp.)Yang et Huang进行了染色体的记数和核型描述,其中后两个种的工作属于首次。此外,本文还首次报道了山蚂蝗属两个种:Des-modium caudatum(Thunb.)DC.和D.yunnanense Franch.的染色体数目。

KARYOTYPE ANALYSIS OF 3 SPECIES OF GENUS PODOCARPIUM AND CHROMOSOME NUMBERS OF 2 SPECIES OF GENUS DESMODIUM

The present paper deals with a study of the karyotype analysis of 3 species of genus Podocarpium and chromosome numbers of 2 species of genus Desmodium. The chromosome numbers and karyotypes of 2 species of genus Podocarpium (P. williamsii (Ohashi)Yang et Huang and P. duclouxii (Pamp.) Yang et Huang) and chromosome numbers of 2 species of genus Desmodium (D. cauda-tum(Thunb.)DC. and D. yunnanense French.)are reported for the first time. The chromosome numbers of 5 species tested have been found to be 2n=22 uniformly. 24 chromosomes are often found in root-tip cells of P. williamsii, on the basis of observing a lot of cells, I find that chromosome number 5 is easily separable into two parts at the kinetochore. I think, therefore, 24 chro-mosomes are result of the separation of chromosome number 5 caused by testing process, not occured naturally. The karyotype formula are as follows:P. podocarpum, 2n=2x=22=18m+4sm P. williamsii, 2n=2x=22=10m+12sm P. duclouxii, 2n=2x=22=14m+8sm Photomicrographs of the chromosome complement and the idiograms are shown in plate Ⅰ and Figs. Ⅰ. Measurements in microns of the chromosome sets are given in Table 2. Accarding to Stebbins, the karyotype of P. podocarpum belongs to 2A, and those of P. williamsii and P. duclouxii belong to 2B.If the karyotype of P. podocarpum is used as representative of Sect. Podocarpium, those of P. williasii and P. duclouxii as represen-tatives of Sect. Repanda, it is easily concluded that Sect. Podo-carpium is less specialized than Sect. Repanda in genus Podocarpium. To confirm this conclusion, further and more study is needed. Among Sect. Repanda, P. williamsii has more asymmetrical or advanced karyotype. The fact suggests that P. williamsii be more advanced than P. duclouxii. Under the same experiment condition, the size of chromosomes of P. duclouxii is found to be significantly larger than that of P. williamsii. Obashi (1980) found that P. oldhamii (Oliv.)Yang et Huang (Desmodium oldhamii Oliv.) had large-sized chromo-somes. Combining gross-morphology, Ohashi considered the species as less specialized than the other species of same section.The separation of P. oldhamii from other species of the section as an independant subsection was confirmed correct. Considering the large-sized chromosomes and special gross-morphology (with tuberous root),I think that it is necessary to separats P. duclouxii from other species of the Sect. Repanda as an independent series.