国产毛茛科驴蹄草属两种植物的细胞学研究

Cytology of Two Species in the Genus Caltha (Ranunculaceae) from China

摘要:

为探讨国产毛茛科(Ranunculaceae)驴蹄草属(Caltha L.)植物的细胞学特征,对驴蹄草(C. palustris L.) 3 个居群和花葶驴蹄草(C. scaposa Hook. f. & Thoms.)5个居群进行了细胞学研究。驴蹄草贵州纳雍居群的染色体数目为2n=32(四倍体),两个云南中甸居群的染色体数目均为2n=64(八倍体)。花葶驴蹄草四川红原、康定、石渠居群的染色体数目均为2n=32(四倍体),该数目为首次报道;西藏林芝和云南德钦居群的染色体数目均为2n=64(八倍体)。驴蹄草的染色体比花葶驴蹄草大。这两种植物的32或64条染色体分别以4条或8条为单位大致能够排列为8组同源染色体,但同一组内的染色体经常具有明显的异形性(heteromorphy),不同居群的核型组成多少具有差异。同时,还分析了驴蹄草和花葶驴蹄草的不同倍性细胞型在我国的地理分布式样。

Abstract:

Three populations in Caltha palustris and five in C. scaposa from China, two closely related species in the small genus Caltha of the Ranunculaceae, have been cytologically investigated. Of the populations checked in C. palustris, the Nayong population from Guizhou has the chromosome number of 2n=32 (tetraploid), and the two Zhongdian populations from Yunnan have the number of 2n=64 (octoploid). Among those checked in C. scaposa, the Hongyuan, Kangding, and Serxu populations from Sichuan all have the tetraploid number of 2n=32, and the Nyingchi population from Xizang and the Deqen population from Yunnan both have the octoploid number of 2n=64. We have performed a karyotypic analysis on most of these populations. The present results, together with those reported previously, show that both C. palustris and C. scaposa from China may have undergone strong differentiation among populations in ploidy level and karyotypic constitution. Caltha palustris from China includes at least three cytotypes with different ploidy levels, namely, the tetraploid cytotype with 2n=32, the hexaploid cytotype with 2n=48, and the octoploid cytotype with 2n=64. The tetraploid cytotype is the commonest and the most widespread, and currently only in northwestern Yunnan all the three cytotypes have been found to co-occur. Caltha scaposa from China includes two cytotypes, the tetraploid cytotype with 2n=32 and the octoploid cytotype with 2n=64, with the former occurring in the northeastern part of the geographical range of the species while the latter in the southwestern part. Although the 32 or 64 chromosomes in both C. palustris and C. scaposa can be roughly arranged into eight groups of four or eight homologues, in some of the groups there often exists obvious heteromorphy among the presumably homologous chromosomes, and thus different populations are more or less distinct in karyotypic constitution. Although C. palustris and C. scaposa are the two most closely related species in the genus, they are revealed to be rather well differentiated chromosomally, particularly in chromosome size. The chromosomes in C. scaposa are smaller than those in C. palustris, which may represent a derived condition.