title: A novel method of measuring leaf epidermis and mesophyll stiffness shows the ubiquitous nature of the sandwich structure of leaf laminas in broad-leaved angiosperm species.
abstract: Plant leaves commonly exhibit a thin, flat structure that facilitates a high light interception per unit mass, but may increase risks of mechanical failure when subjected to gravity, wind and herbivory as well as other stresses. Leaf laminas are composed of thin epidermis layers and thicker intervening mesophyll layers, which resemble a composite material, i.e. sandwich structure, used in engineering constructions (e.g. airplane wings) where high bending stiffness with minimum weight is important. Yet, to what extent leaf laminas are mechanically designed and behave as a sandwich structure remains unclear. To resolve this issue, we developed and applied a novel method to estimate stiffness of epidermis- and mesophyll layers without separating the layers. Across a phylogenetically diverse range of 36 angiosperm species, the estimated Young's moduli (a measure of stiffness) of mesophyll layers were much lower than those of the epidermis layers, indicating that leaf laminas behaved similarly to efficient sandwich structures. The stiffness of epidermis layers was higher in evergreen species than in deciduous species, and strongly associated with cuticle thickness. The ubiquitous nature of sandwich structures in leaves across studied species suggests that the sandwich structure has evolutionary advantages as it enables leaves to be simultaneously thin and flat, efficiently capturing light and maintaining mechanical stability under various stresses.
authors: Section of Plant Ecology and Biodiversity, Institute of Environmental Sciences, Utrecht University, P.O. Box 800.84, 3508TB Utrecht, The Netherlands Department of Agriculture, Kyoto University, Kyoto 606-8502, Japan yusuke.onoda@gmail.com.
authors: Yusuke
authors: Y
authors: Onoda
authors: Section of Plant Ecology and Biodiversity, Institute of Environmental Sciences, Utrecht University, P.O. Box 800.84, 3508TB Utrecht, The Netherlands.
authors: Feike
authors: F
authors: Schieving
authors: Section of Plant Ecology and Biodiversity, Institute of Environmental Sciences, Utrecht University, P.O. Box 800.84, 3508TB Utrecht, The Netherlands Centre for Crop Systems Analysis, Wageningen University, P.O. Box 430, 6700AK Wageningen, The Netherlands.
authors: Niels P R
authors: NP
authors: Anten
mesh_terms: D044822:Biodiversity; D001696:Biomechanical Phenomena; D008027:Light; D019684:Magnoliopsida / Q000033:anatomy & histology* / Q000502:physiology; D010788:Photosynthesis; D018515:Plant Leaves / Q000033:anatomy & histology / Q000502:physiology; D011312:Pressure
keywords: Biodiversity; biomechanics; cuticle; epidermis; evolution; leaf anatomy; mechanical design; mesophyll; sandwich structure; turgor pressure.