水松的细胞学研究

本文报道了水松的核型公式K(2n)=22=22m,为“1A”类型。染色体相对长度组成为2n=22=2L+4M_2+16M_1。8号染色体具长着丝点区域,这是核型的一个特征。与近缘的国产种柳杉和水杉相比较。三者由原始到进化的顺序可能为(柳杉、水松)、水杉,水松与柳杉最接近,水杉和水松较近缘。本文还计算了水松的染色体体积。

CYTOLOGICAL STUDY ON GLYPTOSTROBUS PENSILIS KOCH (TAXODIACEAE)

The present paper deals with the cytological study on Glyptostrobus pensilis (Staunt.) Koch (Taxodiaceae), which is a timber tree endemic to China. The number of somatic chromosomes in seed's root-tip cell has been found to be 2n=22, which all have metacentric centromeres. According to tie terminology defined by Levan et al., the karyotype formula is K (2n)=22=22m, that belongs to "lA" of Stebbins' taryotypic symmetry and is generally regarded as a rather primitive one. In the light of the method of Kuo et al., the species' chromosome complement based on relative length is 2n = 22=2L + 4M2 + 16M1. Among these chromosomes, the size of number 1 is large(L), 2-3 and 4-11 are medium large (M2) and medium small (M1) respectively. The measurements in microns of the chromosomes are given in Table 1. The photomicrograph of the chromosome complement and idiogram of the karyotype are given in Fig. 1 and Fig. 2. It is a character of the karyotype that there is a long kinetochore region on chromosome 8 (Fig. 1, 2). The volume of the somatic complement is 202.52μ3 (Table 2).Although Metasequoia glyptostroboides and Cryptomeria fortunei have the same of "1A" type of karyotypic symmetry as G. pensilis, the differences of their chromosome complements based on relative length, relative lengthes between the longest and the shortest chromosomes and the ratios of the longest chromosome to the shortest (Table 3) have shown that the karyotype of M. glyptostroboides is the most asymmetric one and it seems more advanced than that of the other two, that are much similar with each other. The present author suggests that the sequence of evolutionary level from primitive to progress would be (C. fortunei, G. pensilis), M. glyptostroboides.