中文摘要：

以青藏高原东缘６００种植物种子为对象，就海拔对种子大小的影响展开系统性地研究。结果表明，１）整个区系内，植物种子大小与海拔呈极显著的负相关关系（n＝６００，R2＝０．０２９，P＜０．００１），并且在２０００～３０００ｍ 海拔梯度中，种子大小有先增大后减小的趋势；２）草本植物种子大小与海拔呈极显著的负相关关系（n＝５１２，R2 ＝０．０２６，P＜０．００１），但是灌木（n＝７２，R2＝０．００４，P＝０．６１６）和乔木种子大小（n＝１６，R2＝０．００５，P＝０．７９５）随海拔虽有减小的趋势但无显著相关性；３）海拔较高地区的草本植物种子大小比同属的海拔较低的植物种子大１１．５％（df＝１３１，t＝２．７２４，P＝０．００７），小于阈值±３０％，草本植物属内种子大小与海拔无关。在１３２个草本植物种对中，与同属的低海拔物种相比，４０．９％（５４种）高海拔物种种子大，另外１９．７％（２６种）小，３９．４％（５２种）没有变化，由此，认为在青藏高原东缘强烈的选择压力下，海拔和系统发育综合因子对植物种子大小的影响由具体的某个属本身的特性所决定，不存在单一的海拔与属的种子大小变异模式。

英文摘要：

Seed size was studied in relation to altitude, growth form and phylogeny across 600 species on the eastern Qinghai--Tibet Plateau. 1） Considering the whole flora, seed size decreased with altitude（n=600, R^2 =0. 029, P〈0. 001）, in accord with previous studies; 2） The decline in seed size with altitude was significant within grasses（n= 512 ,R^2 =0. 026,P〈0. 001）, but not within shrubs（n=72, R2=0. 004, P=0. 616）, or trees （n=16, R2=0.005, P=0.795）. 3） t-tests found that seeds of higher region species were 11.5G larger than seeds from lower region species of the same genus（d f= 131, t=2. 724, P=0. 007）, but smaller than the threshold ±30%, so, there was no significant effect between seed size and altitude within a genus. This is in contrast to other studies that have found a positive correlation. Compared with seed size of species collected from lower regions in the 132 grass species-pairs 40.9%（54 species） of, higher species had larger seeds, 19.7%（26 species）had smaller, and 39.4% （52 species）had no difference. There was no uniform pattern relating seed size to altitude. In different genera, seed size responses to environment have varied over long-term ecological time.