中文摘要：

用饱和脉冲调幅式叶绿素荧光测定仪PAM-2100,分别测定了驯化于强光和弱光下的白榆（Ulmus pumila L.）叶片的快速光曲线。结果表明,驯化后的白榆叶片样品,其光合特征值发生明显改变。①强光驯化使得瞬时荧光Ft值升高,弱光驯化下非光化学淬灭系数NPQ高于强光驯化值;②弱光驯化后,吸收能量的比例参数Y（Ⅱ）大大减小,主动散失能量的能力参数Y（NPQ）增加,但是对于结构性保护能力参数Y（NO）影响不大;③强光驯化后的白榆叶片的最大电子传递速率rETRmax远大于弱光驯化后的相应值,相应的初始斜率α和半饱和光强Ik也具有类似的规律。市内环境的光合有效辐射不会对白榆造成光合机构的损伤,强光驯化更有利于白榆的光合作用;在干旱区植物中,白榆具有较强抗性和竞争力;市内绿化规划时,建议将白榆种植在阳光直射处,既可以充分发挥白榆的强光抗性,又可以为一些阴生绿化植物减少阳光直射伤害。

英文摘要：

Rapid light curves provide the detailed information about the saturation characteristics of electron transport and the holistic photosynthetic performance of a plant.In this study,the rapid light curves（RLCs） were measured with PAM-2100 from the leaf samples of Ulmus pumila L.acclimating to low-light〔80 μmol/（m2·s） 〕 and high-light conditions〔80 μmol/（m2·s） 〕,and the distinctive patterns of RLCs parameters were researched in terms of differential sink capacity and PSII reaction centre closure.Derived cardinal points of RLCs（α,Ik and Pm） were used to describe the photosynthetic capacity of U.pumila leaves,its light adaptation and capacity to tolerate a short-term light change.The results are as follows：（1） High-light acclimation made the Ft value increase,and the NPQ under low-light acclimation was higher than that under the highlight acclimation;（2） Y（Ⅱ） corresponding to the fraction of energy converted photochemically in PS II was significantly decreased,Y（NPQ） corresponding to the fraction of energy dissipated in form of heat via the regulated photo-protective NPQ mechanism was increased,but Y（NO） reflecting the fraction of energy passively dissipated in form of heat and fluorescence,mainly due to the closed PS II reaction centers,was kept steadily;（3） The rETRmax value was much higher after high-light acclimation than that after low-light acclimation,and that of corresponding α and Ik was similar.Measurement and fitting of RLCs can provide the information of plant PS Ⅱ,on which we can know the survival ways of plants.