中国特有的八角莲和六角莲的核型

A STUDY ON THE KARYOTYPES OF DYSOSMA VERSIPELLIS AND D. PLEIANTHA ENDEMIC TO CHINA

本文研究了八角莲Dysosma versipellis(Hance)M.Cheng和六角莲Dysomapleiantha((Hance)Woodson的核型。二者的染色体数目均为2n=12,由四对具中部着丝点染色体、一对具近中部着丝点染色体和一对具端部着丝点染色体组成,各有一对染色体具有次缢痕,八角莲的次缢痕在第3对染色体的长臂上,六角莲的次缢痕在第1对染色体的短臂上。二者均属较对称的“2A”核型。但它们在染色体相对长度的变异幅度和差值、臂比的变异幅度和差值以及最长与最短染色体的比值上均有微小的差异。结果表明二者有密切的亲缘关系。演化趋势是八角莲→六角莲。八角莲的核型为首次报道。

The present paper deals with the karyotype of Dysosma versipellis ( Hance ) M. Cheng and D. pleiantha ( Hance ) Woodson. The chromosome number of the two species is 2n=12 and they have the same karyotype formula, i.e.,K(2n ) - 12=8sm( 2SAT ) +2st + 2t. They all have four pairs of M-chromosomes, one pair of ST-chromosomes and one pair of T-chromosomes. The chromosomes of one pairs posses secondary constriction ( see Table 1 and Fig. 1, 2, 3, 4 ); but the position of secondary constriction lying on the chromosome is different. There are secondary constriction on the long arms of 3th pair in D. versipellis ( Hance ) M. Cheng and on the short arms of 1th pair in D. pleiantha ( Hance ) Woodson. They both belong to '2A' type of Stebbins karyotype symmetrey and is generally regarded as a more primitive one. But their range and margin of relative length on chromosomes, range and margin of arm ratio and ratio of the longest chromosome to the shortest chromosome all have a little difference (see Table 2). D. pleiantha ( Hance ) Woodson>D. versipellis ( Hance ) M. Cheng.The result showed a close interspecific relationship in D. versipellis ( Hance ) M. Cheng and D. pleiantha ( Hance ) Woodson. The evolution trend of karyotype is-that D. pleiantha ( Hance ) Woodson is more advanced between the two species in karyotype. The karyotype of D. versipellis ( Hance ) M. Cheng is reported here for the first time.