Doley D, Yates D J, Unwin G L
Department of Botany, University of Queensland, 4067, St. Lucia, Queensland, Australia.
CSIRO Division of Forest Research, P.O. Box 780, 4883, Atherton, Queensland, Australia.
Oecologia. 1987 Dec;74(3):441-449. doi: 10.1007/BF00378943.
Rates of apparent photosynthesis were measured in situ at five positions between the upper crown and a lower branch of a 34 m tall Argyrodendron peralatum (F.M. Bailey) H.L. Edlin ex I.H. Boas tree, and on an understorey sapling of the same species growing in a northern Australian rainforest. At the end of the dry season, rapid reductions in photosynthetic rates occurred in the upper crown within three days after a rain event, but changes in the lower crown and the sapling were less marked. Complete recovery of photosynthesis followed a second rain event. At high photon flux densities, stomatal conductance to water vapour decreased in a curvilinear fashion as the vapour pressure difference between leaf and air increased. Apparent photosynthesis was linearly related to stomatal conductance on the first clear day after each rain event, but there was no relationship between these parameters at the end of a brief natural drying cycle. Under conditions of adequate water supply, stomatal conductances of both upper crown and understorey leaves increased linearly with increasing photon flux density up to about 300 μmol m s. During water deficits, stomatal conductances in leaves from the understorey increased much more rapidly at very low photon flux densities than did conductances in leaves from the upper canopy.
在一棵34米高的澳洲银桦（Argyrodendron peralatum (F.M. Bailey) H.L. Edlin ex I.H. Boas）树的树冠上部和较低树枝之间的五个位置，以及生长在澳大利亚北部雨林中的同一物种的林下幼树原位测量了表观光合速率。在旱季结束时，降雨事件发生三天内，树冠上部的光合速率迅速下降，但树冠下部和幼树的变化不太明显。第二次降雨事件后光合作用完全恢复。在高光子通量密度下，随着叶片与空气之间的蒸汽压差增加，气孔导度呈曲线下降。每次降雨事件后的第一个晴天，表观光合作用与气孔导度呈线性关系，但在短暂的自然干燥周期结束时，这些参数之间没有关系。在水分供应充足的条件下，树冠上部和林下叶片的气孔导度随光子通量密度增加呈线性增加，直至约300 μmol m s。在水分亏缺期间，林下叶片的气孔导度在非常低的光子通量密度下比树冠上部叶片的气孔导度增加得更快。
