中文摘要：

在野外自然条件下设置三个不同光照强度的人工遮阴对青藏高原东缘30种不同生活型禾本科植物种子的萌发行为进行了研究.结果表明：各光照梯度下30种禾本科植物种子的萌发率差异不显著,平均萌发时间差异显著,外在环境因子光照主要影响植物种子萌发的进程.植物在存在竞争的环境中会选择快速萌发来争取幼苗茎杆伸长开始的时间,以截获更多的光资源,提高适合度;各光照梯度下,两种生活型植物种子的萌发率差异显著（多年生的显著高于一年生的）,平均萌发时间差异不显著.说明不同生活型禾本科植物种子萌发行为的差异主要体现在萌发数量上,种子萌发与生活型存在固有而紧密的联系;随着光照强度的减弱,一年生禾本科植物种子萌发进程加快程度高于多年生的,说明一年生禾本科植物种子对光照梯度更为敏感,更加＂珍惜这惟一的机会＂.总之,不同的光照梯度下,植物可能会选择最佳的萌发策略,来扩大其优势度,这种最佳的萌发对策差异因生活型而不同,而生活型的不同归根到底是繁殖对策的不同.

英文摘要：

Three different light intensities of artificial shade were set under natural conditions and the effects of light intensity on seed germination of 30 Poaceae plants from the eastern Qinghai-Tibet plateau were observed.The results of one-way ANOVA showed that under different light intensities no significant difference existed in the germination percentage,but the mean germination time had significant difference.Light only inflenced the process of germination.Seeds would expedite the process of germination to improve their fitness in a competitive environment.Under each light intensity,the germination percentage of perennials was significantly higher than that of annuals,but the mean germination time showed no significant difference between two life forms.The difference of germination between two life form plants was based on quantity.The findings indicated an intrinsic association between seed germination and life form.The mean germination time of neither annuals nor perennials increased with decreasing light intensity;however,the mean germination time of perennials increased more quickly than that of annuals.Seeds of annuals were more sensitive to light intensity than perennial seeds and made better use of this unique opportunity.In a word,under different light intensities plants would choose the best germination strategy to increase their fitness.The best germination strategy is greatly different between annuals and perennias and this difference can be attributed to their different reproducing strategies.