Department of Biology, University of Florida, Gainesville, FL 32611, USA.
New Phytol. 2010 May;186(3):708-21. doi: 10.1111/j.1469-8137.2010.03212.x. Epub 2010 Mar 10.
Leaf toughness is thought to enhance physical defense and leaf lifespan. Here, we evaluated the relative importance of tissue-level leaf traits vs lamina thickness, as well as their ontogenetic changes, for structure-level leaf toughness and regeneration ecology of 19 tropical tree species. We measured the fracture toughness of the laminas and veins of sapling leaves with shearing tests, and used principal component analysis and structural equation modeling to evaluate the multivariate relationships among traits that contribute to leaf toughness and their links to ecological performance traits. Tissue traits (density and fracture toughness of lamina and vein) were correlated positively with each other, but independent of lamina thickness. The tissue traits and lamina thickness contributed additively to the structure-level toughness (leaf mass per area and work-to-shear). Species with dense and tough leaves as saplings also had dense and tough leaves as seedlings and adults. The patterns of ontogenetic change in trait values differed between the seedling-to-sapling and sapling-to-adult transitions. The fracture toughness and tissue density of laminas and veins, but not the lamina thickness, were correlated positively with leaf lifespan and sapling survival, and negatively with herbivory rate and sapling regeneration light requirements, indicating the importance of tissue-level leaf traits.
叶片韧性被认为可以增强物理防御和叶片寿命。在这里，我们评估了组织水平叶片特性与叶片厚度的相对重要性，以及它们在 19 种热带树种的结构水平叶片韧性和再生生态方面的发育变化。我们通过剪切试验测量了幼树叶片的叶层和叶脉的断裂韧性，并使用主成分分析和结构方程模型来评估对叶片韧性有贡献的性状之间的多元关系及其与生态表现性状的联系。组织特征（叶层和叶脉的密度和断裂韧性）彼此之间呈正相关，但与叶片厚度无关。组织特征和叶片厚度对结构水平韧性（叶面积质量和剪切功）有累加贡献。作为幼树的叶片密度大且韧性强的物种，在幼苗和成年期也具有密度大且韧性强的叶片。在从幼苗到幼树和从幼树到成年的过渡中，性状值的发育变化模式不同。叶层和叶脉的断裂韧性和组织密度与叶片寿命和幼树存活率呈正相关，与食草率和幼树再生光需求呈负相关，而叶片厚度与这些性状均无相关性，这表明组织水平叶片特性很重要。
