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在山西省方山县,采用人工控制土壤水分方法,利用模拟光源研究了白榆苗6个土壤水分水平的净光合速率(Pn)、蒸腾速率(Tr)和瞬时水分利用率随光辐射(I)增强的变化规律。结果表明:白榆叶片的Pn、水分利用率在I较低时〔大约0~1500μmol/(m2.s)〕,随I的增强而增大,当I进一步增强,白榆的Pn和水分利用率呈下降趋势;而白榆叶片的Tr在无水分胁迫情况下,始终随I的增强而增大。通过6个土壤梯度水分的比较得出:随土壤水分增加,白榆Pn、Tr和水分利用率的变化趋势先增大后减小。在土壤含水量为5.34%~21.76%时,白榆的光饱和点为750~1542μmol/(m2.s),光补偿点为85~35μmol/(m2.s),由光饱和点对应最大净光合速率为1.28~12.80μmol(CO2)/(m2.s)。
In Fangshan County of Shanxi Province, the net photosynthetic rate (Pn), transpiration rate (Tr) and instantaneous water use efficiency of six soil moisture levels of Ulmus pumila were studied with artificial light source control ) Enhanced change rule. The results showed that the Pn of leaves of Ulmus pumila increased when I was low (about 0 ~ 1500μmol / (m2.s)] with the increase of I. When I was further increased, Pn and water use The rate showed a downward trend; while the leaves of Ulmus pumila under no water stress, with the increase of I always increased. According to the comparison of 6 soil water gradients, the trend of Pn, Tr and water use efficiency of Ulmus pumila increased first and then decreased with the increase of soil moisture. The light saturation point was 750 ~ 1542μmol / (m2.s) and the light compensation point was 85 ~ 35μmol / (m2.s) when soil water content was 5.34% ~ 21.76% Photosynthetic rate was 1.28 ~ 12.80μmol (CO2) / (m2.s).