增补UV-B辐射对高山植物美丽风毛菊叶片PSⅡ光化学效率的影响

Effect of Enhanced UV-B Radiation on PSⅡ Photochemistry Efficiency in Alpine Plants Saussurea superba

太阳紫外线-B(UV-B)辐射增强作为全球环境变化的一个方面,也是影响青藏高原植物生存的主要环境因子之一。以美丽风毛菊(Saussurea superba)为材料,分析增补UV-B辐射期间叶片PSⅡ运行效率(ФPSⅡ)、光化学和非光化学猝灭系数(qP和NPQ),及光合色素和UV-B吸收物质含量的变化,探讨高山植物的UV-B驯化适应过程。结果表明:增补UV-B辐射能抑制暗适应3 min后PSⅡ光化学量子效率F(v)/F(m)的恢复过程;尽管增补前期ФPSⅡ有升高趋势,但第7 d以后ФPSⅡ呈下降趋势,说明UV-B辐射对光合机构具有负影响,F(v)/F(m)的降低以及ФPSⅡ的变化反映了UV-B辐射效应的积累;qP与ФPSⅡ的变化趋势相同,NPQ在第9 d略有降低趋势,叶厚度的相对增加弥补了光合色素的光氧化损失并增强了对激发能的利用。增补UV-B处理对UV-B吸收物质含量的影响不明显,说明叶表皮层内丰富的黄酮类物质能有效保护光合机构,受UV-B辐射波动的影响较少。综上表明,高山植物美丽风毛菊对增补UV-B辐射有一个驯化适应过程,尽管单位叶面积光合色素的增加有益于光合速率的提高,但UV-B辐射增强对光合生理过程仍具有潜在的负效应。

Strong solar UV-B radiation as one factor of global change is a main environmental factor on alpine plants in Qinghai-Tibet region.Based on previous UV-B-supplementation report on alpine plant Saussurea superba,the dynamic changes of PSⅡ operating efficiency,ФPSⅡ,and photochemical and non-photochemical quenching,qP and NPQ,were analyzed during periods of enhancement of UV-B radiation.Results indicated that 3 mins dark adapted quantum efficiency of PSⅡ photochemistry,F（v）/F（m）,was decreased when compared with the UV-A control.PSⅡ operating efficiency,ФPSⅡ,showed an increased trend during the first 7 days of enhanced UV-B radiation treatment then decreased after continuously treatment.This suggested that an accumulation of UV-B radiation damage could reduce PSⅡ photochemistry efficiency.There were similar changes in qP and ФPSⅡ,but NPQ has a decreasing trend at 9 days.This may result from increased photosynthetic pigments due to thicking leaves that absorb and utilize more energy.There was no influence on UV-B-absorbing compounds after enhancing UV-B radiation that suggested flavonoids compounds can provide enough protection on photosynthetic function from UV-B damage.In summary,although photosynthetic pigments enhanced photosynthesis,negative effects still existed especially at the end of plant development.