KARYOTYPE STUDY OF METASEQUOIA GLYPTOSTROBOIDES

Metasequoia glyptostroboides Hu et Cheng (Taxodiaceae) is a timber tree endemic to China. The somatic chromosomes in root-tip cell are found to be 2n=22, all with median constrictions. According to the terminology defined by Levan et al., the karyotype formula is K(2n)=22m(2SAT) which is generally regarded as a rather primitive one. It belongs to "1A" type of Stebbins' karyotypic symmetry. Chromosome7 has a satellite in its short arm. The photomicrographs of the chromosome complement and idiogram of the karyotype are given in Fig. 1 and Fig. 2 respectively. Measurements in micron of the chromosomes are given in Table 1. Chromosome 8, 10, 11 have long kinetochores (See Fig. 1 and Fig.2) which are the character of the species.Saylor analysed the karyotype of Sequoia sempervirens and the result tend to support most strongly its autoallopolyploid (AAAABB) origination suggested by Stebbins. With the karyotypes of M. glyptostroboides and S. sempervirens (AA) being much similar and both belonging to "1A" type (Table 2), the present author support Stebbins' suggestion that the former may actually be a direct descendant of an ancient ancestor of the latter.