贵州大树茶的核型变异与进化

本文对贵州大树茶7种1变种11类型的核型进行了分析。结果表明，这些种类均为二倍体2n＝30。五室茶Camellia quinquelocularis 2n＝30＝24m+6sm；四球茶C．tetracocca 2n＝30=22m+8sm；大理茶C．taliensis 2n=30＝22m+8sm；秃房茶C．gymnogyna 2n＝30＝22m+6sm+2st与2n=30＝20m+8sm+2st；假秃房茶C. gymnogynoides 2n＝30=22m+6sm+2st与2n＝30=20m+8sm+2st；榕江茶C. jungkiangensis 2n＝30+20m+8sm+2st；茶C．sinensis 2n=30＝20m+8sm+2st以及变种淡红花茶C．sinensis var．ruolla 2n＝30=20m+8sm+2st；均属2A核型。染色体结构变异在茶组植物演化中起了重要作用。所划分的两大类核型，即m和sm类与m，sm，和st类是与其子房室数，即5室和3室相一致的。根据核型的不对称性程度、外部形态及生化分析，探讨了各种类的亲缘关系与系统演化途径，论证了茶组植物的原产地是位于滇、桂、黔毗邻交汇处的云贵高原，探讨了茶组植物的分类学问题。

KARYOTYPE VARIATION AND EVOLUTION OF SECT.THEA IN GUIZHOU

Karyotypes of seven species, one variety and 11 forms of Sect. Thea occurring in Guizhou Province, were investigated by the wall degradation hypotonic method. The micrographs of their somatic metaphase are shown in plates 1-2 and the parameters of chromosomes according to Li and Chen (1985) are given in Table 1 and the idiograms in Fig. 1. The karyotype formulae are as follows; Camellia quinquelocularis 22 = 30=24m 6sm; C. tetra-cocca 2n = 30 = 22m 8sni; C. taliensis 2n=30 = 22m 8sm; C. gymnogyna 2n = 30 = 22m 6sm 2st and 2n = 30=20m 8sm-2st; C. gymnogynoides 2n = 30 = 22m 6sm-(-2st and 2n = 30 = 20m 8sm 2st; C. jungkiangensis 2n = 30 = 20m 8sm 2st; C. sinensis 2n = 30=20m 8sm-2st, and C. sinensis var. ruoella 2n=30 = 20m 8sm 2st. All the kary-otypes belong to Stebbins' "2A". The following main aspects are discussed. 1. Chromosome numbers: All these species are found to have 2n=30. Based on the previous and present reports, It clearly indicates that evolution of this group has taken place mainly on diploid level, but not on polyploid one. 2. The karyotype variation; Generally, all the karyotypes examined are similar, but according to symmetry of karyotype, they may be grouped into two types. One is characterized by metacentric (m) and submetacentric (sm) chromosomes, involving C. quinquelochlaris, C. tetracocca, C. taliensis, while the other is characterized by a pair of subtelocentric (st) chromosome besides m and sm chromosomes, involving C. gymnogyna, C. gymnogynoides, C. jungkiangensis, C. sinensis and C. sinensis var. ruoella. It is suggested that the mechanism for karyotype variation and speciation in Sect. Thea be pericentric inversion or reciprocal translocation. The first type is more symmetrical than the second one, and is thus relatively primitive. 3. The orginal center of Sect. Thea: Based on the analysis of karyotypes, morphological characters, geographical distribution and biochemical features, the authors consider that the Yunnan-Guizhou plateau including the contiguous area in Yunnan, Guangxi and Guizhou is the original center, from where it radiated, resulting in the present distribution pattern of Sect. Thea. 4. Taxonomic treatment of Sect. Thea: The taxonomic treatment of Sect. Thea is complicated and still confused up to now. The number of species is more than 40 according to Zhang's taxonomic system (1984), but, recently, most of them are reduced by Min (1992). Further work should be based on the concept of morphological discontinuity and information from other branches of sciences. Whether two types of karyotype are two biological species remains questionable.