云南乌头属牛扁亚属的核形态研究

A KARYOMORPHOLOGICAL STUDY IN ACONITUM SUBGEN LYCOCTONUM(RANUNCULACEAE)FROM YUNNAN

对云南乌头属牛扁亚属（ＡｃｏｎｉｔｕｍＬ．ｓｕｂｇｅｎ，Ｌｙｃｏｃｔｏｎｕｍ）３种、１变种共９个居群的核形态进行了研究。其中弯短距乌头（Ａｃｏｎｉｔｕｍｂｒｅｖｉｃａｌｃａｒａｔｕｍｖａｒ．ｂｒｅｖｉｃａｌｃａｒａｔｕｍ）、粗花乌头（Ａ．ｃｒａｓｓｉｆｌｏｒｕｍ）和滇川乌头（Ａ．ｗａｒｄｉｉ）的染色体数目和核型为首次报道。所有种类的静止核和前期染色体形态基本相似，分别属于复杂中央染色微粒型和中间型；分裂中期染色体数目为２ｎ＝４ｘ＝３２，染色体类型通常为ｓｍ或ｍ，ｓｔ染色体少见，染色体从大到小逐渐过渡，核型的二型性不明显。结合有关资料，重点指出了乌头属不但在亚属之间，而且在牛扁亚属内也存在着较大的核型分化；牛扁亚属与乌头亚属（ＡｃｏｎｉｔｕｍＬ．ｓｕｂｇｅｎ．Ａｃｏｎｉｔｕｍ）在核型上的最重要区别在于前者的二型性通常不明显，而后者有明显的二型性。此外还讨论了牛扁亚属植物的一些分类问题。

Nine populations of four taxa of A conitum subgen. Lycoctonum from Yunnan were karyomorphologically studied.The chromosome numbers of A conitum brevicalcaralum var.brevicalcaratum,A. wardii and A. crassiflorum are reported here for the first time. The results are summarized as follows:1.Karyomorphological type of the resting nuclei and that of the mitotic prophase chromosomes are very similar among the four taxa studied and can be classified as complex chromoeenter type and interstitial type respectively.2.All the four taxa studied are tetraploids with 2n=32,completely or mostly consisting of median-and submedian-centromeric chromosomes,which suggests that Shang et al's generali-zation that the species of subgenus Lycoctonum are mostly diploids,and their chromosomes are mostly subterminal-centromeric ones does not hold true,On the contray,it should be considered that strong karyotypic differentiation has occured in this subgenus in respect of chromosome morphology.3.Most importantly,chromosomes of the four taxa studied are all found to decrease gradu-ally in size from the largest to the smallest,so their karyotypes have no obvious bimodality,and thus show significant differences from the karyotypes of subgenus Aconitum with very conspicu-ous bimodality It is noteworthy that the diploid species of subgenus Lycoctonum,such as A. alboviolaceum and A. barbartum var.puberulum have also such kurylotypes without bimodality as those of the tetraploid species studied here, though their karyotypes have greatly differentiated in respect of chromosome morphology as mentioned above Therefore,it can be concluded that karyotypes have no obvious bimodality is a common, relatively stable and probably primitive characteristics of subgenus Lycoclonum,and is also the most important cytolo gical features to distinguish it from subgenus Aconitum.4.Although strong karyotypic differentiation has occured in subgenus Lycoctonum as em-phasized above, the four taxa studied here are essentially similar in their karyomorphological characteristics,indicating that they might be closely related and thus Lauener and Tamura's put-ting them in three different series might not be advisable.5.A. wardii is found to be a tetraploid with karyotype formula of 2n=8m+22sm+2st or 4m+24sm+4st,while A. leucostomum is a diploid with karyotype formula of 2n = 2m+4sm+10st according to Malakhova's report.Tamura and Lauener reduced the latter species to synonomy of the former.Their treatinent seems quite unreasonable if considering the great differences of karyotypes.In fact,both species are also distinct in external morphology and geographical distri-bution as pointed out by Li.