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Bulletin of Botanical Research ›› 1987, Vol. 7 ›› Issue (3): 123-130.

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Cui Xian-ju   

  1. Institute of Forestry and Soil Science, Academia Sinica, Shenyang, Liaoning
  • Online:1987-06-15 Published:2016-06-13

Abstract: 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.