Institute for Horticultural Production Systems, Leibniz-University Hannover, Herrenhäuser Straße 2, D-30419 Hannover, Germany.
J Exp Bot. 2017 Nov 9;68(19):5351-5367. doi: 10.1093/jxb/erx265.
Cuticles envelope primary surfaces of the above-ground portion of plants. They function as barriers to water movement and to gas exchange, and in pathogen defense. To serve as a barrier on growing organs, cuticles must remain intact but at the same time must accommodate ongoing growth. Minimizing cuticle failure has stimulated significant research on the cuticle's mechanical properties. The objective here is to review the literature on the mechanical properties of isolated fruit and leaf cuticles. Cuticles are viscoelastic polymers. Viscoelasticity results mainly from the cutin matrix. Impregnation by waxes, flavonoids, and cutan increases stiffness and strength but decreases extensibility. On the inner side, the cutin matrix is impregnated by cell wall polysaccharides, which are responsible for its elastic behavior. Across species, the maximum forces sustainable by hydrated cuticles in uniaxial tensile tests averaged 0.82 N (range 0.15-1.63 N), the maximum stresses averaged 13.2 MPa (range 2.0-29.0 MPa), the maximum strains averaged 8.8% (range 1.6-28.0%), and the moduli of elasticity averaged 224 MPa (range 60-730 MPa). Among the environmental factors, high temperature and hydration both decreased stiffness. Therefore, the mechanical properties of cuticles in vivo depend largely on the relative proportions of their constituents. These proportions change during development and are also affected by environmental factors such as temperature.
表皮包裹着植物地上部分的初级表面。它们的功能是作为水运动和气体交换的屏障，并在病原体防御中发挥作用。为了在生长器官上充当屏障，表皮必须保持完整，但同时必须适应持续的生长。为了尽量减少表皮的失效，人们对表皮的机械性能进行了大量研究。这里的目的是回顾关于分离的果实和叶片表皮机械性能的文献。表皮是粘弹性聚合物。粘弹性主要源于角质层基质。蜡、类黄酮和角质的浸渍增加了硬度和强度，但降低了伸展性。在内侧，细胞壁多糖浸渍角质层基质，这使其具有弹性行为。在不同物种中，水合表皮在单轴拉伸测试中可持续承受的最大力平均为 0.82 N（范围 0.15-1.63 N），最大应力平均为 13.2 MPa（范围 2.0-29.0 MPa），最大应变平均为 8.8%（范围 1.6-28.0%），弹性模量平均为 224 MPa（范围 60-730 MPa）。在环境因素中，高温和水合作用都会降低硬度。因此，表皮的机械性能在很大程度上取决于其成分的相对比例。这些比例在发育过程中发生变化，并且还受到环境因素（如温度）的影响。
