Bamboo Research Institute, College of Biology and the Environment, Nanjing Forestry University, Nanjing, 210037, China.
Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Tartu, 51006, Estonia.
Am J Bot. 2022 Jun;109(6):899-909. doi: 10.1002/ajb2.1856. Epub 2022 Jun 1.
Across species, main leaf vein density scales inversely with leaf area (A). Yet, minor vein density manifests no clear relationship with respect to A, despite having the potential to provide important insights into the trade-off among the investments in leaf mechanical support, hydraulics, and light interception.
To examine this phenomenon, the leaves of nine Magnoliaceae leaves were sampled, and the scaling relationships among A and midrib length (ML), total vein length (TVL), total vein area (TVA), total areole area (TAA), and mean areole area (MAA) were determined. The scaling relationships between MAA and areole density (the number of areoles per unit leaf area) and between MAA and A were also analyzed.
For five of the nine species, A was proportional to ML . For eight of the nine species, TVL and TVA were both proportional to A. The numerical values of the scaling exponents for TAA vs. A were between 1.0 and 1.07 for eight species; i.e., as expected, TAA was isometrically proportional to A. There was no correlation between MAA and A, but MAA scaled inversely with respect to areole density for each species.
The correlation between midrib "density" (i.e., ML/A) and A, and the lack of correlation between total leaf vein density and A result from the A ML scaling relationship and the proportional relationship between TVL and A, respectively. Leaves with the same size can have widely varying MAA. Thus, leaf size itself does not directly constrain leaf hydraulic efficiency and redundancy.
在不同物种中，主叶脉密度与叶面积（A）呈反比。然而，尽管小脉密度有可能提供有关叶片机械支撑、水力和光截获之间权衡取舍的重要见解，但它与 A 之间没有明显的关系。
为了研究这一现象，对木兰科的 9 种叶片进行了采样，并确定了 A 与中脉长度（ML）、总叶脉长度（TVL）、总叶脉面积（TVA）、总网眼面积（TAA）和平均网眼面积（MAA）之间的比例关系。还分析了 MAA 与网眼密度（单位叶面积的网眼数）之间的关系以及 MAA 与 A 之间的关系。
对于 9 种中的 5 种，A 与 ML 成正比。对于 9 种中的 8 种，TVL 和 TVA 均与 A 成正比。8 种物种的 TAA 与 A 的比例指数值在 1.0 到 1.07 之间；即，正如预期的那样，TAA 与 A 是等比的。MAA 与 A 之间没有相关性，但对于每个物种，MAA 与网眼密度成反比。
中脉“密度”（即 ML/A）与 A 之间的相关性以及总叶片叶脉密度与 A 之间缺乏相关性，是由于 A 与 ML 的比例关系以及 TVL 与 A 的比例关系所致。具有相同大小的叶片可以具有广泛变化的 MAA。因此，叶片大小本身不会直接限制叶片水力效率和冗余度。
