西藏自治区日喀则市白草核型分析

白草（Pennisetum centrasiaticum）广泛分布于世界各地，被牛羊所采食。本试验采用常规根尖压片法对采自西藏日喀则市的白草进行染色体数目统计及核型分析。结果表明：白草染色体总长度为45.87 μm，平均臂比为1.23，核型不对称指数为54.83；所有染色体的臂比在1.08至1.70范围内，其中近中部着丝粒染色体（sm）为1对，其余17对均为中部着丝粒染色体（m），所有染色体未观测到随体出现；白草染色体基数为9，核型为2n=4x=36=34 m+2 sm，属于四倍体植物，核型类型为1A，是进化较原始的物种。

Karyotype Analysis of Pennisetum centrasiaticum in Shigatse,Tibet

Pennisetum centrasiaticum is widely distributed all over the world ,and it is kind of forage grazed by cat-tle and sheep .In this study ,a conventional squash technique was used to analyze the karyotype of P .centrasiatic-um collected from shigatse .Results showed that the sum of chromosome lengths was 45 .87 μm ,the average arm ratio of chromosome was 1 .23 ,and the index of karyotypic asymmetry was 54 .83 .All chromosomes with the arm ratio ranged from 1 .08 to 1 .70 ,one pair of chromosomes was sm ,and the remaining chromosomes were m .There was no satellite on the chromosome of P .centrasiaticum .The basic chromosome number was 9 ,and P .centrasi-aticum was a tetraploid plant with karyotype formula 2n=4x=36=34 m+2 sm ,and belonged to Stebbins' 1A type .It meant P .centrasiaticum was a primitive species in evolution .