增补UV-B辐射对高山植物美丽风毛菊光合作用和光合色素的影响

Effect of Enhanced UV-B Radiation on Photosynthesis and Photosynthetic Pigments in Alpine Plants Saussurea superba

强太阳紫外线-B(UV-B)辐射是青藏高原的主要环境胁迫因子,以高山植物美丽风毛菊(Saussurea superba)为材料,在2008和2009年植物生长盛期的7,8月份,采用选择性过滤膜和UV-B荧光灯管组合的方法研究了净光合速率(Pn)、稳态PSⅡ光化学效率、光合色素和紫外线吸收物质对强UV-B辐射的响应,探讨了典型高山植物的UV-B适应特性。结果表明:增补UV-B辐射能引起Pn和气孔导度(Gs)的增加;随处理时间的延长,第11和16天PSⅡ实际量子效率(ΦPSⅡ)呈下降趋势,说明UV-B辐射对高山植物叶片光合机构仍具有负作用,PSⅡ光化学效率的降低反映了UV-B辐射效应的积累。增补初期光合色素有增加的趋势,但随处理时间的延长最终呈降低趋势,表明UV-B辐射对光合色素的光破坏是本质的,而基于叶片厚度增加导致的光合色素含量升高是一种表象。增补UV-B处理没有引起紫外线吸收物质含量的变化,表明高山植物叶表皮层丰富的黄酮类物质能有效保护光合机构,受环境UV-B辐射波动的影响较少。综上表明:增补UV-B后叶片Gs的增加以及单位叶片面积光合色素增加有利于Pn的提高,但青藏高原强太阳UV-B辐射对高山植物美丽风毛菊的光合生理过程仍具有潜在的负效应。

Strong solar UV-B radiation is the main environmental stress factors in Qinghai-Tibet region.A UV-B-supplementation study was performed in alpine Kobresia humilis meadow using cellulose diacetate filtered fluorescence UV-B lamps,comparing to the control lamps with a Mylar film in order to remove UV-B emission.Results from alpine plant Saussurea superba indicated that net photosynthetic rate,Pn,was enhanced after supplementing solar UV-B intensity,resulting from the opening of stomatal conductance.However,ΦPSⅡ showed a decrease after 11 and 16 days of treatment,suggesting that accumulation of damage from UV-B radiation could reduce PSⅡ photochemistry efficiency.Although there was an increase of photosynthetic pigments within the first 10 days of treatment,they decreased by the end of experiment indicating that UV-B radiation causes photo-damage of photosynthetic pigments and that the initial increase of its contents was mainly due to the increase of leaf thickness.UV-B-absorbing compounds were not altered after enhancement of UV-B radiation suggesting that there were higher levels of flavonoid compounds in the epidermal layer of S.superba acting to protect photosynthetic function from UV-B damage.In summary,the short-term enhanced UV-B radiation was beneficial for Gs and photosynthetic pigments,but there were still negative effects on photosynthesis function of this native alpine plant.