关键词: UV-B辐射变化, 高寒草甸, 光合作用, 麻花艽, 青藏高原

Abstract: This study describes the effects of temperature changes and enhanced UV-B radiation on net photosynthesis and related physiological parameter of straw-yellow gentian(Gentiana straminea Maxim.).Samples were analyzed using 20 W and 40 W UV-B lamps to increase UV-B radiation and with LI-6400 portable photosynthesis systems to change air temperature.Results show that net photosynthetic rate(P_n),stomata conductance(G_s),intercellular CO₂ concentration(C_i),transpiration rate(E) and water use efficiency(WUE) of straw-yellow gentian was higher under control than that under 20W or 40 W UV-B lamp treatments,while P_n at 25℃ was higher than that at 15℃ under increasing UV-B radiation treatments in August or under controls in September.Additionally,E of straw-yellow gentian at 25℃ was higher than that at 15℃,while G_s,C_i or WUE of straw-yellow gentian at 25℃ was lower than that at 15℃ under increasing UV-B radiation treatments.Results also show that P_n of straw-yellow gentian increased with increasing photosynthetic active radiation(PAR) when the PAR ranged from 0~800 μmol·m^-2·s^-1,while maximizing when PAR ranged from 800~2200 μmol·m^-2·s^-1,but no change when the PAR ranged from 2200~3000 μmol·m^-2·s^-1.The G_s or E of straw-yellow gentian increases with increased the PAR.The C_i of straw-yellow gentian decreases with increased PAR when the PAR ranged from 0~800 μmol·m^-2·s^-1,but did not change when the PAR ranged from 800~3000 μmol·m^-2·s^-1.The WUE of straw-yellow gentian increases with increased the PAR when the PAR ranged from 0~800 μmol·m^-2·s^-1,and it decreases slowly when PAR ranged from 800~3000 μmol·m^-2·s^-1.Results indicate that enhanced UV-B radiation results in decreased P_n,G_s,C_i,E and WUE of alpine meadows leaves that would be influenced by temperature variation.

Key words: UV-B radiation change, Photosynthesis, Alpine Meadows, Straw-Yellow Gentian, Qinghai-Tibet Plateau