Blackman Chris J, Brodribb Tim J
School of Plant Science, University of Tasmania, Private Bag 55, Hobart, Tas. 7001, Australia.
Funct Plant Biol. 2011 Feb;38(2):118-126. doi: 10.1071/FP10183.
The efficiency and stress tolerance of leaf water transport are key indicators of plant function, but our ability to assess these processes is constrained by gaps in our understanding of the water transport pathway in leaves. A major challenge is to understand how different pools of water in leaves are connected to the transpiration stream and, hence, determine leaf capacitance (Cleaf) to short- and medium-term fluctuations in transpiration. Here, we examine variation across an anatomically and phylogenetically diverse group of woody angiosperms in two measures of Cleaf assumed to represent bulk-leaf capacitance (Cbulk) and the capacitance of leaf tissues that influence dynamic changes in leaf hydration (Cdyn). Among species, Cbulk was significantly correlated with leaf mass per unit area, whereas Cdyn was independently related to leaf lignin content (%) and the saturated mass of leaf water per unit dry weight. Dynamic and steady-state measurements of leaf hydraulic conductance (Kleaf) agreed if Cdyn was used rather than Cbulk, suggesting that the leaf tissue in some species is hydraulically compartmentalised and that only a proportion of total leaf water is hydraulically well connected to the transpiration stream. These results indicate that leaf rehydration kinetics can accurately measure Kleaf with knowledge of the capacitance of the hydraulic pathway.
叶片水分运输的效率和耐胁迫能力是植物功能的关键指标，但我们评估这些过程的能力受到对叶片水分运输途径理解不足的限制。一个主要挑战是了解叶片中不同的水分库如何与蒸腾流相连，从而确定叶片对蒸腾作用短期和中期波动的电容（Cleaf）。在这里，我们研究了一组在解剖学和系统发育上具有多样性的木本被子植物在两种Cleaf测量指标上的变化，这两种指标分别假定代表叶片整体电容（Cbulk）和影响叶片水分动态变化的叶片组织电容（Cdyn）。在不同物种中，Cbulk与单位面积叶质量显著相关，而Cdyn则独立地与叶片木质素含量（%）和单位干重叶片水的饱和质量相关。如果使用Cdyn而不是Cbulk，叶片水力导度（Kleaf）的动态和稳态测量结果是一致的，这表明某些物种的叶片组织在水力上是分隔的，并且只有一部分总叶片水分在水力上与蒸腾流良好连接。这些结果表明，在了解水力途径电容的情况下，叶片再水化动力学可以准确测量Kleaf。
