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落羽杉属植物的核型及细胞地理学研究

李林初   

  1. (复旦大学生物系,上海)
  • 收稿日期:1900-01-01 修回日期:1900-01-01 出版日期:1988-10-18 发布日期:1988-10-18
  • 通讯作者: 李林初

The Studies on the Karyotypes and Cytogeography of Taxodium Rich.(Taxodiaceae)

Li Lin-Chu   

  1. (Departmcnt  of  Biology,  Futan  University,  Shanghai)
  • Received:1900-01-01 Revised:1900-01-01 Online:1988-10-18 Published:1988-10-18
  • Contact: Li Lin-Chu

摘要:

本文分析了池杉Taxodium ascendens 的核型,全由中部和近中部着丝点染色体组成,
核型公式为K(2n)=22=20m+2sm,属“1A”类型。它的特点是10号染色体具“长着
丝点区域”结构。池杉染色体的相对长度组成为2n=2L+8M2+12M1。通过与落羽杉
的“1A”和墨西哥落羽杉的“2A”核型进行比较,似见它们的进化水平以落羽杉、池杉,墨西
哥落羽杉之序递增。  落羽杉属植物的核型公式均为K(2n)=22= 20m+2sm。  本文还就
核型、生态环境和地理分布(包括化石)资料讨论了落羽杉属的次生遗传歧异中心和可能的演
化式样。  

关键词: 落羽杉属, 核型, 细胞地理学

Abstract:

The present paper deals with the karyotypic analysis of Taxodium ascendens Brongn.
The somatic chromosomes in root-tip cells of the plant are found to be 2n =22, all with median
and submedian constrictions.  A character of the karyotype is that the   chromosome 10 has
a long kinetochore region (Plate 1:1).  According to the terminology defined by Levan et al.[18],
the karyotype formula is k(2n)=22=20m+2sm, which is different to  Huang  et  Hsu’s[8]
K(2n)=24=22m+2B(m).  The karyotype belongs to “lA” of Stebbins’[24] karyotypic symmetry
and is generally regarded as a relatively primitive one.   The species’ chromosome complement
is 2n=22=2L+8M2+12M1 according to I.R.L.difined by Kuo et al.[15] based on relative length.
The lengths, arm ratios and types of chromosomes of the species are given in Table 1-I.  The
morphology of the chromosomes and the karyotype, are given in Plate 1:1.
      In the light of the works of Schlarbaum et al.[21] and Mehra et al.[17], K(2n)=22=20m
(2SAT)+2sm and 2n=22=2L+6M2+14M1 are for T. distichum (L.) Rich. (see Table 1-II),
K(2n)=20m+2sm and 2n=22=4L+4M2+12M1+2S for T. mucronatum Tenore (see Table
1-III, Plate 1:2), which belong to “lA” and “2A” respectively.
     The differences between three species in the ratio of the longest to the shortest chromosome,
I.R.L. and the proportion of chromosomes with arm ratio >2 show that the karyotype of T.
mucronatum is the most advanced and that of T. distichum the  most  primitive.   The present
author suggests that the sequence of evolutionary advance be T. distichum, T. ascendens, T. mu-
cronatum.
      Based on the evidence from the karyotype analyses, ecology and geographical distribution
(including fossil), the secondary center of genetic diversity (Fig. 1) and the probable evolu-
tionary pattern (Fig. 2) of Taxodium are discussed.

Key words: Taxodium, Karyotype, Cytogeography