Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
Faculty of Agriculture, Food and Natural Resources, University of Sydney, NSW 2570, Australia.
New Phytol. 2012 Mar;193(4):939-947. doi: 10.1111/j.1469-8137.2011.04014.x. Epub 2012 Jan 6.
Previous research suggests that the lifetime carbon gain of a leaf is constrained by a tradeoff between metabolism and longevity. The biophysical reasons underlying this tradeoff are not fully understood. We used a photosynthesis-leaf water balance model to evaluate biophysical constraints on carbon gain. Leaf hydraulic conductance (K(Leaf)), carbon isotope discrimination (Δ(13)C), leaf mass per unit area (LMA) and the driving force for water transport from stem to leaf (ΔΨ(Stem-Leaf)) were characterized for leaves spanning three orders of magnitude in surface area and two orders of magnitude in lifespan. We observed positive isometric scaling between K(Leaf) and leaf area but no relationship between Δ(13)C and leaf area. Leaf lifespan and LMA had minimal effect on K(Leaf) per unit leaf area, but a negative correlation exists among LMA, lifespan, and K(Leaf) per unit dry mass. During periods of leaf water loss, ΔΨ(Stem-Leaf) was relatively constant. We show for the first time that K(Leaf, mass), an index of the carbon cost associated with water use, is negatively correlated with lifespan. This highlights the importance of characterizing K(Leaf, mass) and suggests a tradeoff between resource investment in liquid phase processes and structural rigidity.
先前的研究表明，叶子的终身碳增益受到代谢和寿命之间的权衡限制。这种权衡的生理基础尚未完全了解。我们使用光合作用-叶片水分平衡模型来评估碳增益的生理限制。叶片水力传导率（K（Leaf））、碳同位素分馏（Δ（13）C）、单位面积叶片质量（LMA）和从茎到叶的水分运输驱动力（ΔΨ（Stem-Leaf））被用于特征化叶片，这些叶片的表面积跨越三个数量级，寿命跨越两个数量级。我们观察到 K（Leaf）与叶面积之间存在正等距缩放关系，但 Δ（13）C 与叶面积之间没有关系。叶片寿命和 LMA 对单位叶面积的 K（Leaf）影响最小，但 LMA、寿命和单位干质量的 K（Leaf）之间存在负相关关系。在叶片水分丧失期间，ΔΨ（Stem-Leaf）相对恒定。我们首次表明，与水利用相关的碳成本指数 K（Leaf，mass）与寿命呈负相关。这突出了表征 K（Leaf，mass）的重要性，并表明在液相过程和结构刚性的资源投资之间存在权衡。
