UV-B辐射增强对麻花艽叶片光合作用及相关生理参数的影响

采用20 W和40 W的UV-B灯辐射增强处理，测定分析了UV-B辐射增强对麻花艽(Gentiana straminea Maxim)叶片净光合速率及相关生理参数的影响. 结果显示:2008年8月3日，研究区大气温度从09:00开始上升，到14:00达到最高点，叶温和大气饱和水气压变化与气温变化趋势相似；光合有效辐射强度从07:00开始上升，至13:00达到最高，之后下降；麻花艽叶片净光合作用速率(P_n)、气孔导度(G_s)、胞间CO₂浓度(C_i)、蒸腾速率(E)和水分利用效率在对照下最高，在40 W UV-B辐射下最低；P_n在08:00—10:00最高，G_s在07:00—08:00最高，C_i在日出及日落时最高，E在09:00—13:00及14:00—18:00最高，水分利用效率在日出后最高；P_n与G_s，叶片温度，大气温度，光合有效辐射和大气饱和水气压亏缺呈正相关，与C_i呈负相关，与光合有效辐射强度的相关系数较高. P_n在光合有效辐射强度为0～800 μmol/(m2·s)时随光合有效辐射强度增加而增加，在2 200～3 000 μmol/(m2·s)时变化不大；G_s和E随光合有效辐射强度的增加而增加；C_i在光合有效辐射强度为0～800 μmol/(m2·s)时，随光合有效辐射强度的增加而呈下降趋势；水分利用效率在光合有效辐射强度为0～800 μmol/(m2·s)时随光合有效辐射强度的增加而呈增加的趋势，在800～3 000 μmol/(m2·s)时呈下降趋势. 说明UV-B辐射增强将使高寒草甸植物叶片P_n，G_s，C_i，E和水分利用效率降低. 

Effects of Enhanced UV-B Radiation on the Photosynthesis and Related Physiological Parameters of Straw-Yellow Gentian (Gentiana straminea Maxim)

The effects of enhanced UV-B radiation on the laminae net photosynthetic rate and related physiological parameters of straw-yellow gentian (Gentiana straminea Maxim) were determined and analyzed by using 20 W and 40 W UV-B lamps to increase the UV-B radiation. The results showed that air temperature in the studied area began to rise from 09:00 am and peaked at 14:00. The variation trend of leaf temperature was similar with that of the atmospheric saturated vapor pressure and air temperature on August 3rd, 2008. The photosynthetic active radiation (PAR) intensity began increasing at 07:00 am, peaked at 13:00, and then decreased. The laminae 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 were the highest under the control treatment, and lowest under 40 W UV-B lamp treatment. P_n was the highest from 08:00-10:00; G_s was the highest from 07:00-08:00; C_i was the highest at time of sunrise or sunset; E was the highest at 09:00-13:00 or 14:00-18:00; and, WUE was the highest after sunrise. P_n was positively related with G_s, leaf temperature, atmosphere temperature, PAR or atmospheric saturated vapor pressure deficit, and negatively related with Ci. The correlation coefficient between P_n and PAR was higher. Additionally, the results showed that P_n increased with increasing PAR when the PAR ranged from 0-800 μmol/(m2·s), but it varied little when the PAR ranged from 2200-3000 μmol/(m2·s). G_s and E increased with increasing PAR. C_i decreased with increasing PAR when the PAR ranged from 0-800 μmol/(m2·s). WUE increased with increasing PAR when the PAR ranged from 0- 800 μmol/(m2·s), but decreased when PAR ranged from 800- 3000 μmol/(m2·s). The results indicated that enhanced UV-B radiation would result in decreases of P_n, G_s, C_i, E or WUE of alpine meadows leaves.