Department of Botany, Institute of Ecology and Earth Sciences, Tartu University, Lai 40, Tartu 51005, Estonia.
Tree Physiol. 2013 Feb;33(2):202-10. doi: 10.1093/treephys/tps112. Epub 2012 Nov 25.
We investigated changes in chlorophyll a fluorescence from alternate leaf surfaces to assess the intraleaf light acclimation patterns in combination with natural variations in radiation, leaf angles, leaf mass per area (LMA), chlorophyll content (Chl) and leaf optical parameters. Measurements were conducted on bottom- and top-layer leaves of Tilia cordata Mill. (a shade-tolerant sub-canopy species, sampled at heights of 11 and 16 m) and Populus tremula L. (a light-demanding upper canopy species, sampled at canopy heights of 19 and 26 m). The upper canopy species P. tremula had a six times higher PSII quantum yield (Φ(II)) and ratio of open reaction centres (qP), and a two times higher LMA than T. cordata. These species-specific differences were also present when the leaves of both species were in similar light conditions. Leaf adaxial/abaxial fluorescence ratio was significantly larger in the case of more horizontal leaves. Populus tremula (more vertical leaves), had smaller differences in fluorescence parameters between alternate leaf sides compared with T. cordata (more horizontal leaves). However, optical properties on alternate leaf sides showed a larger difference for P. tremula. Intraspecifically, the measured optical parameters were better correlated with LMA than with leaf Chl. Species-specific differences in leaf anatomy appear to enhance the photosynthetic potential of leaf biochemistry by decreasing the interception of excess light in P. tremula and increasing the light absorptance in T. cordata. Our results indicate that intraleaf light absorption gradient, described here as leaf adaxial/abaxial side ratio of chlorophyll a fluorescence, varies significantly with changes in leaf light environment in a multi-layer multi-species tree canopy. However, this variation cannot be described merely as a simple function of radiation, leaf angle, Chl or LMA, and species-specific differences in light acclimation strategies should also be considered.
我们研究了来自交替叶片表面的叶绿素 a 荧光变化，以评估叶片内的光适应模式，同时结合辐射、叶片角度、比叶质量（LMA）、叶绿素含量（Chl）和叶片光学参数的自然变化。测量在椴树（一种耐荫下层物种，在 11 米和 16 米处采样）和欧洲山杨（一种喜光上层物种，在树冠高度 19 米和 26 米处采样）的底层和顶层叶片上进行。上层物种 P. tremula 的 PSII 量子产量（Φ(II))和开放反应中心比（qP）比 T. cordata 高六倍，LMA 比 T. cordata 高两倍。当两种叶片处于相似的光照条件下时，也存在这些种间差异。叶片的近轴/远轴荧光比值在叶片更水平的情况下显著更大。与 T. cordata（更水平的叶片）相比，P. tremula（更垂直的叶片）在交替叶片之间的荧光参数差异较小。然而，对于 P. tremula，光学特性在交替叶片之间显示出更大的差异。在种内，所测量的光学参数与 LMA 的相关性优于与叶片 Chl 的相关性。叶片解剖结构的种间差异似乎通过减少 P. tremula 中过量光的截获并增加 T. cordata 的光吸收率来增强叶片生物化学的光合作用潜力。我们的结果表明，这里描述的作为叶绿素 a 荧光近轴/远轴侧比值的叶片内光吸收梯度，在多层多物种树冠中随叶片光环境的变化而显著变化。然而，这种变化不能仅仅描述为辐射、叶片角度、Chl 或 LMA 的简单函数，还应考虑光适应策略的种间差异。
