对一年生杂交马褂木 (Liriodendron chinense Sarg .×L .tulipifera L .)叶片展开过程中光能转换效率、水分利用效率和光合碳同化的变化规律及栽植密度对中下部叶片资源利用效率的影响进行了研究 ,结果表明 :(1)叶片展开过程中 ,净光合速率 (Pn)、气孔导度 (Gs)、蒸腾速率 (E)、气孔限制值 (Ls)、总光合速率 (Pm)、净光合比率 (Pn Pm)、PSⅡ的原初光能转化效率 (Fv Fm)和PSⅡ的光量子产率 (φPSⅡ )、羧化效率 (CE)和水分利用效率 (WUE)显著上升 ,而胞间CO2 浓度 (Ci)和呼吸速率 (R)显著下降 ;(2 )叶片展开过程中 ,光合碳同化“暗系统”的完善远远慢于能量转换的“光系统” ;(3)叶片展开过程中 ,影响净光合速率增长的主导因素不是气孔导度 ,而是“暗系统”完善程度 ,“光系统”的影响远小于“暗系统”的影响 ;(4)郁闭的高密度群体中 ,中下部叶片的Pn、Gs、E、Ls、Pm、Fv Fm、φPSⅡ、CE和WUE显著低于上部完全展开叶 ,Ci显著高于上部完全展开叶 ,Pn Pm和上部完全展开叶没有显著差异 ,而未郁闭的低密度群体中 ,中下部叶片的上述所有参数与上部完全展开叶无显著差异 ;(5 )导致高密度群体叶片Pn大幅度下降的主导因素是CE的大幅下降 ,而不是“光系统”和气孔导度 ;(6 )密度过大加速了中下部叶片光合功能的下降 。

Characteristics of light energy use efficiency, carbon dioxide assimilation capacity and water use efficiency in leaves of Liriodendron chinense Sarg.×L . tulipifera L. during leaf developing process and influence of density on middle lower leaves were studied. The results are as follows: ( 1) During leaf developing, net photosynthetic rate ( Pn) , stomatal conductance ( Gs) , transpiratory rate ( E) , stomatal limitation ( Ls) , mass photosynthetic rate ( Pm) , net photosynthesis ratio ( Pn Pm) , maximal PS Ⅱ efficiency at open centers in the absence of NPQ ( Fv Fm) , actual PS Ⅱ efficiency (φ PS Ⅱ) , carboxylation efficiency ( CE) and water use efficiency (WUE) increased significantly, while intercellular CO2 concentration ( Ci) and respiratory rate ( R) decreased significantly; ( 2) During leaf developing, the photosystem Ⅱ got perfect much more quickly than dark system; ( 3) During leaf developing, the chief factor, which led to significant increase in Pn, lied in significant increase in CE, not in significant increase in Fv Fm, φ PS Ⅱ or Gs; ( 4) In high density, such parameters in middle lower leaves as Pn, Gs, E, Ls, Pm, Fv Fm, φ PSⅡ, CE and WUE were all much smaller than those in full expansion leaves at nodes above, while Ci was much larger than that in full expansion leaves at nodes above. However, as for Pn Pm, there was no significant difference in full expansion leaves at nodes above and below ; ( 5) In high density, the chief factor, which led to significant decrease in Pn, lied in significant decrease in CE and not in decrease in Fv Fm or Gs; ( 6) Higher density to excess quickened remarkably the aging course of photosynthetic apparatus in leaves.