Karyomorphology of four species in Ancylostemon,Briggsiopsis and Lysionotus (Gesneriaceae)

Reported in the present paper are chromosome numbers and karyotypes of three genera of the Gesneriaceae, i.e. Ancylostemon Craib. , Briggsiopsis (Franch.) K. Y. Pan and Lysionotus D. Don. The former two genera are endemic to China. The karyotype of Ancylostemon aureus (Franch.) Burtt is formulated as 2n = 34 = 20m(1sat) + 14sm, with the same chromosome number as its allied species A. convexus Craib. This species is characterized by the interphase nucleus of complex chromocenter type and the proximal type of chromosomes in the mitotic prophase. The chromosome number of the monospecific genus Briggsiopsis is 2n = 34, the same as the lowest chromosome number reported in Briggsia. The karyotype of Briggsiopsis, which is formulated as 2n = 25m + 6sm + 3st, also seems to be primitive among the species of the two genera. Briggsiopsis is characterized by the interphase nucleus of simple-complex chromocenter type and the interstitial-gradient type of chromosomes in the mitotic prophase. The chromosome number of Lysionotus carnosus Hemsl. is the lowest reported in this genus. Its karyotype is formulated as 2n= 30 = 21m + 5sm + 3st + lt. Lysionotus serratus var. pterocaulis, with the karyotype being formulated as 2n= 32 = 2lm + 10sm + lt, has the same chromosome number as var. serratus. These two species show a remarkable differentiation of karyotypes and are characterized by the interphase nuclei of simple-complex chromocenter type and the gradient type of chromosomes in the mitotic prophase. _ .     

直瓣苣苔属、筒花苣苔属和吊石苣苔属4个种的核形态学研究

本文报道了苦苣苔科直瓣苣苔属Ancylostemon、筒花苣苔属Briggsiopsis和吊石苣苔属Lysionotus 中4个种的染色体数目和核形态。凹瓣苣苔A．aureus的染色体数目为n=34,与其近缘种凸瓣苣苔 A．convexus的染色体数目相同。该种的核型公式为2n=20m(1sat)+14sm,核型类型属于2A。间期核 为复杂染色中心型(complex chromocenter type);细胞有丝分裂前期的染色体为近基型(proximal type) 我国特有单种属筒花苣苔属Briggsiopsis的间期核为简单—复杂染色中心型(simple-complex chromocenter type);细胞有丝分裂前期的染色体为中间—渐变型(interstitial—gradient type);核型公式为2n=34=25m +6sm+3st,与近缘类群——粗筒苣苔属Briggsia染色体数目2n=34,68相比,无论染色体数目还是核 型均显示比较原始的特征。吊石苣苔属的蒙自吊石苣苔L．carnosus和翅茎吊石苣苔L．serratus D． Don var．pterocaulis的核型公式分别是2n=30=21m+5sm+3st+1t和2n=32=21m+10sm+1t。核 型类型分别属于2A和2B。间期核均为简单—复杂染色中心型(simple-complex chromocenter type);细胞 有丝分裂前期的染色体为渐变型(gradient type)。