青藏高原强UV-B辐射对美丽风毛菊光合作用和色素含量的影响

以青藏高原矮嵩草草甸的主要伴随种美丽风毛菊为材料，通过滤除太阳辐射光谱中UV-B成分的模拟试验，研究了强太阳UV-B辐射对高山植物光合作用、光合色素和紫外吸收物质的影响.结果表明：与对照相比，弱UV-B处理能促使美丽风毛菊叶片净光合速率增加和提高稳态PSⅡ光化学效率；对照中叶片厚度的相对增加能弥补单位叶面积光合色素的光氧化损失，是高山植物对强UV B辐射的一种适应方式.短期滤除UV-B辐射处理时紫外吸收物质含量几乎没有变化，说明高山植物叶表皮层中该类物质受环境波动的影响较小.强UV-B环境下光合色素的相对增加是一种表象，而青藏高原强太阳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影响.

Effects of strong solar UV-B radiation on photosynthesis and photosynthetic pigment contents of Saussurea superba on Qinghai-Tibet Plateau

Taking the main companion species Saussurea superba in an alpine Kobresia humilis meadow on Qinghai-Tibet Plateau as test material, a UV-B
exclusion experiment with UV-B excluding and UV-B transmitting filters was performed to study the effects of strong solar UV-B on the photosynthesis, photosynthetic pigments, and UV-B-absorbing compounds of S. superba, aimed to examine the adaptation capability of alpine plants to strong solar UV-B radiation. The removal of UV-B components from natural sunlight increased the net photosynthetic rate (P<0.05) and PSⅡ photochemistry efficiency of S. superba. The relatively increased leaf thickness under ambient UV-B could compensate the photo-oxidation of photosynthetic pigments, an inherent characteristic of alpine plants growing in intense UV-B. Short-term removal of UV-B radiation had no obvious effects on the UV-B absorbing compounds, suggesting that these compounds in epidermal layer of S. superba could hardly be affected by the environment. It was concluded that the increase of photosynthetic pigment contents due to the enhancement of leaf thickness was a specious phenomenon, but the strong solar UV-B radiation on Qinghai-Tibet Plateau still had a potential negative impact on the photo-physiological processes in alpine plant S. superba.