青藏高原东北部植物染色体数目和多倍性研究

STUDIES OF THE CHROMOSOME NUMBERS AND POLYPLOIDY FOR SOME PLANT IN THE NORTH-EAST QINGHAI-XIZANC PLATEAU

对青藏高原东北部高山冰缘地区和相邻低海拔地区５９种多年生草本被子植物进行了染色体计数。其中，４５个种的染色体记数为首次报道，并确定其信性．对分布于高山冰缘地区和冰缘以下不同海拔地区植物染色体的多倍性进行分析研究，结果如下：（１）多年生草本被子植物多倍体频率随海拔高度上升而增加：海拔２０００－３０００ｍ，多倍体频率为２９．４％－４７．１％．３０００－３８００（４０００）ｍ（高寒灌丛－草甸区），多倍体频率为３３．３％－５３．３％；４０００－５２００ｍ以上的高山冰缘地区，多倍体频率达５５．６％－７０．４％．（２）高山冰缘地区新多倍体较多，并且与青藏高原上特有的植物类群（特有属、亚属或特有种）相关联。（３）分布在冰缘地区的多倍体广布种，通常都是较原始类群的古多倍体，它们可能在青藏高原强烈隆升以前就已经形成，并分化出许多生态型，在高原强烈隆升并出现高山冰缘环境以后，某些生态型突出繁殖适应机制（ｒ型选择机制），能开拓新生境而在新出现的严酷而不稳定的冰缘地区繁衍，其它一些生态型则依靠营养生长优势（Ｋ型选择机制）广泛分布在其稳定、成熟的生境中．（４）冰缘以下地区的多倍体特有种多数属于古多倍体或次生多倍体．它们多数可能是由西?

Meiotic chromosome numbers are determined for fifty-eight species of the pernnialherbceous angiosperm in alpine periglacial area of the North-East Qinghai-XizangPlateau and neighbor lower altitude area. The chromosome numbers include counts forforty-five species that have not previously been investigated cytologically. The polyploidy are analysed and studied for the plants distributed on periglacial area and lower different altitude area below periglacial area. The result as follow t 1. The frequency of polyploid inceases with a rise of altitude for pernnial herbceous angiosperm in North-EastQinghai-Xizang Plateau, in the forest area between 2000- 3000m a. s. 1., 29. 4% - 47.1 % are the percentage of polyploid;in the bush-meadow area between 3000-4000m a.s. 1.,polyploid percentage is 33. 3% - 53. 3% ;in the alpine periglacial area above 40005200m a. s. l.,the polyploid frequency are 55. 6% -70. 4%. 2. Most of the neopolyploidscorrelated always with endemic taxa (included endemic genus,endemic subgenus and endemic species)in alpine periglacial area. 3. The polyploid widespread species distributedto periglacial area are usually early polyplod of more primitive taxa,probably they hadalredy been produced and had alredy been divided into some ecological type before theQinghai-Xizang Plateau was rised. After the plateau had been intensely rised and preiglacial environment had been formed,the ecological types which laid stress on adaptingto propagation mechanism (r-type selective mechanism) have pioneered new habitat inthe periglacial area of Qinghai-Xizang Plateau,anothe ecological types which deperdedon adapting to nutritive growing preponderance (k-type selective mechanism) havewildely destributed in the mature stable habitat of other area. 4. Below to palaeopolyploid or secondary polyploid, that originated in forest flora of the Chinese southwestmoutains and Qin Ling and North China,then have spread towards the edge of the Qinghai-Xizang Plateau.