中文摘要：

通过短期增补UV-B辐射模拟试验,研究了青藏高原典型天气（晴天、多云、阴天）下高山植物美丽风毛菊叶片的叶绿素荧光参数变化.结果表明：随天气由晴变阴,美丽风毛菊叶片暗适应3min的PSⅡ最大光化学量子效率（Fv/Fm）显著升高,实际PSⅡ光化学效率（ΦPSⅡ）和光化学猝灭系数（qP）也升高,而非光化学猝灭系数（NPQ）则降低,可见光辐射（PAR）是影响PSⅡ光能转化效率的主要因素.增补UV-B辐射后,3种典型天气下,美丽风毛菊叶片的Fv/Fm和NPQ略有降低,ΦPSⅡ和qP略微增加,但对光合气体交换过程没有产生负影响.叶片净光合速率Pn和ΦPSⅡ的增高趋势与增补UV-B辐射下相对较多的UV-A成分有关,同时也得益于叶片厚度的增加.UV-B辐射对叶片光合机构具有潜在负影响.

英文摘要：

A simulation experiment of short term supplementation of UV-B was conducted to study the changes of chlorophyll fluorescence coefficients of alpine plant Saussurea superba under three typical weather conditions（sunny,cloudy,and shady） in Qinghai-Tibet Plateau.When the weather changed from sunny to shady,the maximal quantum efficiency of PS Ⅱ photochemistry（Fv/Fm） after 3 minutes of dark adaptation increased significantly,the actual photochemical efficiency of PSⅡ（ΦPSⅡ） and photochemical quenching（qP） also increased,but the non-photochemical quenching（NPQ） decreased,demonstrating that PAR was the main factor affecting the PSⅡ photochemical efficiency of S.superba.After the short term supplementation of UV-B,the Fv/Fm and NPQ under the three typical weather conditions had a slight decrease but the ΦPSⅡ and qP had a slight increase,while the photosynthetic gas exchange had less change.The increasing trend of net photosynthetic rate Pn and ΦPSⅡ under enhanced UV-B radiation could be related to the existence of more UV-A component,and also,benefited from the increased leaf thickness.UV-B radiation had potential negative effects on leaf photosynthetic components.