Yao Weihao, Shi Peijian, Wang Jinfeng, Mu Youying, Cao Jiajie, Niklas Karl J
Co-Innovation Center for Sustainable Forestry in Southern China, Bamboo Research Institute, Nanjing Forestry University, #159 Longpan Road, Nanjing 210037, China.
College of Landscape Architecture, Nanjing Forestry University, #159 Longpan Road, Nanjing 210037, China.
Plants (Basel). 2024 Aug 22;13(16):2340. doi: 10.3390/plants13162340.
The "leafing intensity premium" hypothesis proposes that leaf size results from natural selection acting on different leafing intensities, i.e., the number of leaves per unit shoot volume or mass. The scaling relationships among various above-ground functional traits in the context of this hypothesis are important for understanding plant growth and ecology. Yet, they have not been sufficiently studied. In this study, we selected four bamboo species of the genus Nakai and measured the total leaf fresh mass per culm, total non-leaf above-ground fresh mass, total number of leaves per culm, and above-ground culm height of 90 culms from each species. These data were used to calculate leafing intensity (i.e., the total number of leaves per culm divided by the total non-leaf above-ground fresh mass) and mean leaf fresh mass per culm (i.e., the total leaf fresh mass per culm divided by the total number of leaves per culm). Reduced major axis regression protocols were then used to determine the scaling relationships among the various above-ground functional traits and leafing intensity. Among the four species, three exhibited an isometric (one-to-one) relationship between the total leaf fresh mass per culm and the total non-leaf above-ground fresh mass, whereas one species () exhibited an allometric (not one-to-one) relationship. A negative isometric relationship was found between the mean leaf fresh mass per culm and the leafing intensity for one species (), whereas three negative allometric relationships between mean leaf fresh mass per culm and leafing intensity were observed for the other three species and the pooled data. An exploration of the alternative definitions of "leafing intensity" showed that the total number of leaves per culm divided by the above-ground culm height is superior because it facilitates the non-destructive calculation of leafing intensity for species. These results not only confirm the leafing intensity premium hypothesis for bamboo species but also highlight the interconnected scaling relationships among different functional traits, thereby contributing to our understanding of the ecological and evolutionary significance of leaf size variation and biomass investment strategies.
“展叶强度溢价”假说提出，叶片大小是自然选择作用于不同展叶强度的结果，即单位茎体积或质量的叶片数量。在此假说背景下，各种地上功能性状之间的比例关系对于理解植物生长和生态学很重要。然而，它们尚未得到充分研究。在本研究中，我们选择了中井竹属的四种竹子，测量了每个物种90根茎的每茎总叶鲜质量、地上非叶总鲜质量、每茎总叶数和地上茎高。这些数据用于计算展叶强度（即每茎总叶数除以地上非叶总鲜质量）和每茎平均叶鲜质量（即每茎总叶鲜质量除以每茎总叶数）。然后使用主轴回归方法来确定各种地上功能性状与展叶强度之间的比例关系。在这四个物种中，有三个物种的每茎总叶鲜质量与地上非叶总鲜质量之间呈现等速（一对一）关系，而一个物种呈现异速（非一对一）关系。对于一个物种，每茎平均叶鲜质量与展叶强度之间发现了负等速关系，而对于其他三个物种和汇总数据，观察到每茎平均叶鲜质量与展叶强度之间有三个负异速关系。对“展叶强度”替代定义的探索表明，每茎总叶数除以地上茎高更优，因为它便于对物种进行展叶强度的无损计算。这些结果不仅证实了竹子物种的展叶强度溢价假说，还突出了不同功能性状之间相互关联的比例关系，从而有助于我们理解叶片大小变异和生物量投资策略的生态和进化意义。
