长期增强UV-B辐射对高寒草甸植物光合速率和抗氧化系统的影响

研究了在野外自然条件下，长期增强UV-B辐射对高寒草甸3种典型植物矮嵩草（Kobresia humilis）、垂穗披碱草（Elymus nutans）和钉柱委陵菜（Potentilla saundersiana）光合放氧速率、光合色素和抗氧化系统的影响。结果表明：长期增强UV-B辐射对3种植物的净光合速率没有明显影响。增强UV-B辐射下，3种植物的叶绿素含量变化不同，Chla／b值，类胡萝卜素（Car）含量，Car／Chl值与对照相比都有升高，说明植物叶片的光合能力、吸收紫外线的能力增强以及忍受逆境能力均有增强，从而产生光保护，有利于光合作用正常进行。由于3种植物膜脂过氧化程度的不同及SOD活性的普遍抑制，植物经受了氧化胁迫。垂穗披碱草叶片GSH含量显著七升，矮嵩草的形态矮小及钉柱委陵菜GSH含量与POD活性显著上升，都能减轻它们所经受的氧化胁迫，使光合器官免受损伤。所以，这些保护性色素的积累和抗氧化系统内部的协同作用可能是高寒草甸植物光合作用正常进行的重要原因。

Effects of Long-term Intensified UV-B Radiation on the Photosynthetic Rates and Antioxidative Systems of Three Plants in Alpine Meadows

The effects of long term intensified UV-B radiation on the photosynthetic rates and pigments,and antioxidative systems of three typical plants, Kobresia humilis, Elymus nutans and Potentilla saundersiana, in alpine meadows were studied in the field. The results showed that long-term intensified UV-B radiation did not remarkably affect the net photosynthetic rates of the three plants. Under the intensified UV-B radiation, the chlorophyll contents of the three plants varied differently with the chlorophyll a/b ratios and the carotinoid contents and the carotinoid/chlorophyll ratios increasing compared with those in the control, and this indicated that the photosynthetic, ultra-violet-absorbing and adversity-resisting capabilities of the three plants were enhanced so that light protection took place in the plants and benefited their normal photosynthesis. The three plants suffered oxidation stress because their membrane lipids were oxidized in varying degrees and their SOD activities were all inhibited. The increased GSH content in the leaves of Elymus nutans, the dwarfed plants of Kobresia humilis and the increased GSH contents and enhanced POD activity in Potentilla saundersiana could alleviate oxidation stress so as to keep the photosynthetic organs of the plants from the damages. Therefore, the accumulation of these protective pigments and the synergistic effects in the antioxidant systems may be the reason why photosynthesis can go on in the plants of alpine meadows.