Department of Agro-environmental Science, Obihiro University of Agriculture and Veterinary Medicine, Inadacho, Obihiro, Hokkaido, Japan.
Department of Botany, University of Wisconsin-Madison, 430 Lincoln Dr., Madison, WI, USA.
Ann Bot. 2022 Sep 6;130(2):215-230. doi: 10.1093/aob/mcac043.
An individual plant consists of different-sized shoots, each of which consists of different-sized leaves. To predict plant-level physiological responses from the responses of individual leaves, modelling this within-shoot leaf size variation is necessary. Within-plant leaf trait variation has been well investigated in canopy photosynthesis models but less so in plant allometry. Therefore, integration of these two different approaches is needed.
We focused on an established leaf-level relationship that the area of an individual leaf lamina is proportional to the product of its length and width. The geometric interpretation of this equation is that different-sized leaf laminas from a single species share the same basic form. Based on this shared basic form, we synthesized a new length-times-width equation predicting total shoot leaf area from the collective dimensions of leaves that comprise a shoot. Furthermore, we showed that several previously established empirical relationships, including the allometric relationships between total shoot leaf area, maximum individual leaf length within the shoot and total leaf number of the shoot, can be unified under the same geometric argument. We tested the model predictions using five species, all of which have simple leaves, selected from diverse taxa (Magnoliids, monocots and eudicots) and from different growth forms (trees, erect herbs and rosette herbs).
For all five species, the length-times-width equation explained within-species variation of total leaf area of a shoot with high accuracy (R2 > 0.994). These strong relationships existed despite leaf dimensions scaling very differently between species. We also found good support for all derived predictions from the model (R2 > 0.85).
Our model can be incorporated to improve previous models of allometry that do not consider within-shoot size variation of individual leaves, providing a cross-scale linkage between individual leaf-size variation and shoot-size variation.
一株植物由不同大小的枝条组成，每个枝条又由不同大小的叶片组成。为了根据单个叶片的响应来预测植物水平的生理响应，有必要对枝条内叶片大小的变化进行建模。在冠层光合作用模型中，已经对植株内叶片性状的变化进行了很好的研究，但在植物生长分析中则研究较少。因此，需要整合这两种不同的方法。
我们专注于一个已建立的叶片层面关系，即单个叶片的面积与叶片长度和宽度的乘积成正比。该方程的几何解释是，来自同一物种的不同大小的叶片具有相同的基本形状。基于这种共享的基本形式，我们合成了一个新的长度乘以宽度的方程，该方程从构成枝条的叶片的整体尺寸预测总枝条叶片面积。此外，我们还表明，几个已建立的经验关系，包括总枝条叶片面积、枝条内最大单个叶片长度和总叶片数之间的生长分析关系，可以在相同的几何论证下统一起来。我们使用来自不同分类群（木兰类、单子叶植物和真双子叶植物）和不同生长形式（乔木、直立草本和莲座草本）的 5 个物种进行了模型预测测试，这些物种均具有简单叶片。
对于所有 5 个物种，长度乘以宽度的方程都可以高精度地解释枝条内叶片总面积的种内变化（R2＞0.994）。尽管叶片尺寸在物种间的变化非常不同，但这些强关系仍然存在。我们还发现模型预测的所有衍生预测都得到了很好的支持（R2＞0.85）。
我们的模型可以被纳入到之前没有考虑单个叶片在枝条内大小变化的生长分析模型中，从而在单个叶片大小变化和枝条大小变化之间提供了跨尺度的联系。
