蟛蜞菊属和孪花菊属(菊科-向日葵族)的细胞学研究

Cytology of Sphagneticola and Wollastonia, Two Genera in Heliantheae, Asteraceae

摘要:

研究了菊科向日葵族鳢肠亚族蟛蜞菊属(Sphagneticola O. Hoffm.)和孪花菊属(Wollastonia DC. ex Decne.)各2种植物的染色体数目和染色体形态。蟛蜞菊[S. calendulacea (L.) Pruski]的染色体数目为2n=50, 核型公式为2n=18m+30sm+2st,南美蟛蜞菊[S. trilobata (L.) Pruski]的染色体数目为2n=56, 核型公式为2n=24m+28sm+4st, 孪花菊[W. biflora (L.) DC.]的染色体数目为2n=30,核型公式为2n=24m+4sm+2st,山孪花菊[W. montana (Blume) DC.]的染色体数目为2n=74, 核型公式为2n=37m+31sm+6st。根据上述结果并结合以前的有关资料,推测蟛蜞菊属的染色体基数可能为x=14和x=25,而不应是x=15。该属的3个新世界热带种[S. brachycarpa (Baker) Pruski、S. gracilis (Richard) Pruski和南美蟛蜞菊]可能都基于x=14, 其中S. gracilis为二倍体(2n=2x=28), S. brachycarpa和南美蟛蜞菊为四倍体(2n=4x=56); 唯一的亚洲种(蟛蜞菊)可能是基于x=25的二倍体(2n=2x=50)。染色体资料不支持将山孪花菊(x=37)这一植物置于孪花菊属(x=15)中。

Abstract:

Chromosome number and chromosome morphology in Sphagneticola O. Hoffm. and Wollastonia DC. ex Decne., two small genera in Ecliptinae, Heliantheae, Asteraceae, were investigated. The results showed that the karyotype formula were followed as: Sphagneticola calendulacea (L.) Pruski, 2n=50=18m+30sm+2st, S. trilobata (L.) Pruski, 2n=56=24m+28sm+4st, Wollastonia biflora (L.) DC., 2n=30=24m+4sm+2st, and W. montana (Blume) DC., 2n=74=37m+31sm+6st. Based on the results, together with chromosomal data previously reported in Sphagneticola, we postulate the basic chromosome numbers of this genus as x=14 and x=25, rather than x=15. The three species native to the New World tropics in the genus, namely S. brachycarpa (Baker) Pruski, S. gracilis (Richard) Pruski and S. trilobata, may be based on x=14, with S. gracilis being diploid (2n=2x=28), and both S. brachycarpa and S. trilobata tetraploid (2n=4x=56); the only Asian species, S. calendulacea, may be diploid (2n=2x=50) based on x=25. The systematic implication of this chromosome number pattern is worthy of a further study. Chromosomal data do not support the placement of W. montana (x=37) in the genus Wollastonia (x=15).