长苞铁杉的核型分析及其分类学意义

本文首次分析了特产我国的长苞铁杉亚属(Subgen. Paleotsuga)的代表种长苞铁杉Tsuga longibracteata的核型,它全由中部和近中部着丝粒染色体组成,核型公式为K(2n)=24=22m 2sm,属“lA”类型。第12号染色体具“长着丝点区域”。染色体相对长度组成为2n=12M_2 10M_1 2S。作者发现铁杉亚属(Subgen. Tsuga)植物的核型全为“2A”类型。胞核学资料支持对长苞铁杉亚属和铁杉亚属的划分并表明前者(长苞铁杉)较为原始。长苞铁杉应隶于长苞铁杉亚属、长苞铁杉组。

THE KARYOTYPE ANALYSIS OF TSUGA LONGIBRACTEATA AND ITS TAXONOMIC SIGNIFICANCE

The present paper deals with the karyotype analysis of Tsuga longibracteata Cheng endemic to China, which is a represent species of subgen. Paleotsuga, for the first time. The somatic chromosomes in root-tip cells of the plant are found to be 2n = 24, all with median and submedian constrictions. The 12th chromosome of the karyotype has a long centromere region. According to the terminology defined by levan et al. (1964), the karyotype formula is K(2n) = 24 = 22m 2sm. The karyotype belongs to "1A"of stebbins' (1971) karyotypic symmetry and is generally regarded as a relatively primitive one. The species' chromosome complement is 2n = 12M2- 10M1 2S according to I. R. L. defined by Kuo et al. (1972) based on relative length. In the light of the works of Li (1988) and Hizume (1988), the author found that the karyotypic type "2A"was for all the species in Subgen. Tsuga. The karyological data supported the division of Genus Tsuga into Subgen. Paleotsuga and Subgen. Tsuga and shew the former was more primitive than the latter. The species Tsuga longibracteata Cheng should belong to Genus Tsuga, Subgen. Paleotsuga and Sect. Hepsopeuce.