In this study,the natural variation of the seed characteristics of Sophora moorcroftiana,a Tibet plateau endemic plant,was investigated. Twelve representative natural populations were selected in terms of the principle that sampling points ( groups ) would cover the whole distribution area of S. moorcroftiana and taking into account the differences in habitat area. The pod length,pod width,number of seeds per pod,seed transverse diameter,longitudinal diameter and thousand-grain weight for every groups were measured,and based on these data the phenotypic diversity within and between natural populations of S. moorcroftiana was analyze by using the coefficient of variation,the nested variance analysis and cluster analysis methods. The results showed that:1) the variation in 6 seed characteristics among the populations reached significant level,and the variation in 6 seed characteristics within populations also reached significant level except thousand-grain weight. There existed relatively rich diversity within and between groups,and the mean phenotypic differentiation coefficient ( VST ) among populations was 39. 25%,less than that within populations (60. 75%);2) there were no significant relationships between the six seed characteristics and longitude and latitude, however,the characteristics were significantly correlated with altitude,mean annual temperature and precipitation. The pod became shorter and thicker,the seed number per pod reduced and the seed size became bigger with the increase of elevation;3) the 12 natural populations of S. moorcroftiana were clustered into four categories using Euclidean distance of UPGMA cluster.
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