中文摘要：

以高山植物美丽风毛菊为材料,在矮嵩草草甸植物群落生长季的不同月份,采用短期滤除太阳辐射光谱中UV-B成分的方法,研究了UV-B辐射对PSⅡ光化学效率、光合色素和紫外吸收物质的影响。结果表明,1）与对照相比,low UV-B处理时3min暗适应的PSⅡ最大光化学量子效率Fv/Fm呈升高的趋势,说明UV-B辐射能加剧PSⅡ反应中心的可逆失活或损伤程度。2）PSⅡ实际光化学效率ΦPSⅡ和光化学猝灭系数qP在生长季内具有基本一致的变化趋势;low UV-B处理能引起ΦPSⅡ和qP的升高和NPQ的降低,表明自然光谱中的UV-B成分能降低叶片的光能捕获效率,促进非光化学能量耗散过程。3）low UV-B处理时光合色素的降低与叶片变薄有关,强太阳UV-B辐射下光合色素的相对增加是一种表象。综上可知,青藏高原强太阳UV-B辐射对高山植物的光合生理过程具有潜在的负影响,叶片中高含量且相对稳定的UV-B吸收物质可有效屏蔽太阳UV-B光量子抵达光合机构等敏感部位,不同生育期叶片PSⅡ光化学效率的差异与环境因子和叶片发育状态有关。

英文摘要：

A UV-B-exclusion study was performed in alpine Kobresia humilis meadow during plants growing season.The PSⅡ photochemistry efficiency,photosynthetic pigments and UV-B-absorbing compounds were measured on native alpine plant Saussurea superba.1） The 3 min dark adapted quantum efficiency of PSⅡ photochemistry,Fv/Fm,showed an increasing trend after a short-term removal UV-B radiation from natural sunlight in all measurements.These means there were photo-inactivation and/or photo-damage of photosynthesis occurred in PSⅡ reaction center.2）There were same tendency in PSⅡ photochemistry efficiency ΦPSⅡ and photochemical quenching qP for all measurements during plants growing season;The ΦPSⅡ and qP were increased and NPQ decreased after removal UV-B treatment,which means that there was an increasing in PSⅡ photochemistry efficiency and a decreasing in non-photochemical quenching and current solar UV-B intensity can impair photosynthetic function.3）The reduction of photosynthetic pigments contents were mainly caused by the reducing of leaf thickness and relative increase of photosynthetic pigments contents in amb UV-B treatment a specious phenomenon.In summary,strong solar UV-B radiation in Qinghai-Tibet region has a potential negative influence on photosynthetic physiology process in S.superba.UV-B-absorbing compounds were not influenced during the short-term removal of UV-B radiation,mainly due to strong stabilization of these compounds existed in the epidermal layer of the alpine plant S.superba and can provide effective defense against the natural solar UV-B intensity.