夏须草属的核型研究

KARYOTYPE STUDY OF THE GENUS THEROPOGON

In the present paper, the somatic chromosome number and karyotype of the monotypic genus Theropogon (including the only species T. pallidus) in the tribe Convallarieae were investigated. The chromosome number in the root tip cells was counted to be 40, which is in accord with that reported by Kurosawa. The karyotype is given here for the first time and formulated as 2n = 26m+12sm+2st(sat). The 9th pair of chromosomes have centromeres at the subterminal positons, with a satellite respectively on their short arms, and the satellites are longer than the short arms. The chromosomes decrease gradually in size from the largest to the smallest, so the karyotype is monomodal and belongs to Stebbins' 2B type. Compared with the other genera in the tribe Convallarieae, such as Convallaria, Reineckia, Rohdea, Tupistra and Aspidistra, Theropogon is different from them in its basic chromosome number, karyotype classification (especially from Speirantha, Aspidistra and those species of Tupistra with karyotype of 2C) as well as chromosome size, though its satellite chromosomes are similar to those of Speirantha, Rohdea, Tupistra and Aspidistra. According to Tang et al. and Ma et al., there are also some significant differences between Theropogon and the other genera in tribe Convallarieae in other important characters suchas pollen morphology, which, together with the results of the present paper, suggests that the systematic position of Theropogon in the tribe Convallarieae might be problematic, but the present authors still support the opinion of Tang et al., would like neither hastily to give it a subtribe or tribe rank nor to transfer it to another tribe before an overall study.