光辐射强度对侧柏油松幼苗光合特性与水分利用效率的影响

 探讨不同土壤水分条件下光辐射强度对侧柏和油松苗木光合特性与水分利用效率的影响规律,可为林木栽培和管理提供科学依据。在黄土半干旱区,采用人工控制土壤水分的方法,利用模拟光源研究了侧柏和油松苗木的净光合速率、蒸腾速率、水分利用效率和胞间CO2浓度随模拟光辐射增强的变化规律。结果表明:在模拟光辐射为0～2200μmol/（m2.s）的范围内,侧柏和油松叶片的净光合速率、蒸腾速率和水分利用效率均随光辐射强度的增强而增大,但光辐射强度进一步增强,侧柏和油松净光合速率和水分利用效率呈下降趋势;在同样土壤水分条件下,侧柏净光合速率、蒸腾速率和水分利用效率高于油松,侧柏光饱和点高于油松,而侧柏光补偿点低于油松,侧柏光能利用率高于油松;随着土壤水分的增加,侧柏与油松净光合速率、蒸腾速率和胞间CO2浓度升高,而水分利用效率降低。在土壤含水量为7.90%、13.00%和19.99%条件下,侧柏光饱和点分别为1275、1 450和1 675μmol/（m2.s）,光补偿点分别为4225和13μmol/（m2.s）,由光饱和点对应最大净光合速率分别为3.04、4.06和5.53μmol/（m2.s）;在土壤含水量为7.83%1、3.04%与20.15%条件下,油松光饱和点分别为11001、325和1500μmol/（m2.s）,光补偿点分别为60.30和23μmol/（m2.s）,由光饱和点对应最大净光合速率分别为1.08、3.35和4.36μmol/（m2.s）。

Effects of light radiation intensity on photosynthetic characteristics and water use efficiency to seedlings of Platycladus orientalis and Pinus tabulaeformis

In order to offer scientific base for cultivation and management of forest,effects of light radiation intensity on photosynthetic characteristics and water use efficiency of Platycladus orientalis and Pinus tabulaeformis were studied under different soil moisture content.Controlling soil moisture,under the simulated light photosyntyhetic radiation（SPR）,net photosynthetic rate （P_n）,transpiration rate（T_r）,water use efficiency（WUE） and intercellular CO₂ concentration（C_i） of Platycladus orientalis and Pinus tabulaeformis was studied in a semi-arid region of loess plateaus.The results showed that within the range of 0（2200）μmol photons/（m²·s）,P_n,Tr and WUE enhanced with an increase of the SPR for Platycladus orientalis and Pinus tabulaeformis,but P_n and WUE of Platycladus orientalis and Pinus tabulaeformis declined with continued increase of the SPR;P_n,T_r,WUE and light saturation point（LSP） of Platycladus orientalis was higher than Pinus tabulaeformis,while light compensation point（LCP） of Platycladus orientalis was lower than Pinus tabulaeformis in the same soil moisture,efficiency of light energy utilization of Platycladus orientalis was higher than Pinus tabulaeformis;P_n,T_r and Ci of Platycladus orientalis and Pinus tabulaeformis enhanced with an increase of the soil moisture,while WUE declined.The LSP of Platycladus orientalis was respectively（1275）,（1450） and（1675）μmol photons/（m²·s）,and LCP was respectively（4225） and 13μmol/（m²·s）,with the maximum P_n of 3.04,4.06 and 5.53μmol/（m²·s）,under the soil moisture of 7.90%,13.00% and 19.99%;The LSP of Pinus tabulaeformis was respectively（1100）,（1325） and（1500）μmol/（m²·s）,and LCP was respectively 60,30 and 23μmol/（m²·s）,with the maximum P_n of 1.08,3.35 and 4.36μmol/（m²·s）,under the soil moisture of 7.83%,13.04% and 20.15%.