Department of Biology, University of York York, UK.
Front Plant Sci. 2015 Feb 11;6:35. doi: 10.3389/fpls.2015.00035. eCollection 2015.
Understanding interactions between grasses and their herbivores is central to the conservation of species-rich grasslands and the protection of our most important crops against pests. Grasses employ a range of defenses against their natural enemies; silicon-based defenses have been shown to be one of the most effective. Silicon (Si) is laid down on the leaf surface as spines and other sharp bodies, known as phytoliths, making grasses abrasive and their foliage indigestible to herbivores. Previous studies on Si defenses found that closely related species may have similar levels of Si in the leaves but differ markedly in abrasiveness. Here we show how the number, shape and distribution of Si-rich phytoliths and spines differ within and between different grass species and demonstrate that species also differ in their ability to change the deposition and distribution of these defenses in response to damage or increases in Si supply. Specifically, we tested the response of two genotypes of Festuca arundinacea known to differ in their surface texture and three different grass species (F. ovina, F. rubra, and Deschampsia cespitosa) differing in their abrasiveness to combined manipulation of leaf damage and Si supply. F. arundinacea plants with a harsh leaf surface had higher Si content and more spines on their leaf surface than soft varieties. F. ovina and D. cespitosa plants increased their leaf Si concentration and produced an increase in the number of leaf spines and phytoliths on the leaf surface in response to Si addition. F rubra also increased leaf Si content in response to treatments, particularly in damaged leaves, but did not deposit this in the form of spines or increased densities of phytoliths. We discuss how the form in which grasses deposit Si may affect their anti-herbivore characteristics and consider the ecological and agricultural implications of the differences in allocation to Si-based defenses between grass species.
理解草本植物与其食草动物之间的相互作用对于保护物种丰富的草原和保护我们最重要的作物免受害虫侵害至关重要。草本植物会对其天敌采用一系列防御措施；已证实硅基防御是最有效的防御措施之一。硅（Si）以刺和其他尖锐体的形式沉积在叶片表面，称为植硅体，使草本植物变得粗糙，其叶片对食草动物不可消化。之前关于 Si 防御的研究发现，亲缘关系密切的物种叶片中的 Si 含量可能相似，但耐磨性差异显著。在这里，我们展示了不同草本植物之间和内部 Si 丰富的植硅体和刺的数量、形状和分布如何不同，并证明物种在响应损伤或 Si 供应增加而改变这些防御的沉积和分布的能力方面也存在差异。具体来说，我们测试了两种已知表面质地不同的 Festuca arundinacea 基因型和三种不同的草种（F. ovina、F. rubra 和 Deschampsia cespitosa）对叶片损伤和 Si 供应的综合处理的反应。具有粗糙叶片表面的 F. arundinacea 植物叶片表面的 Si 含量和刺的数量高于柔软品种。F. ovina 和 D. cespitosa 植物在叶片表面增加了叶片 Si 浓度，并增加了叶片刺和植硅体的数量，以响应 Si 的添加。F rubra 也响应处理增加了叶片 Si 含量，特别是在受损叶片中，但不以刺或植硅体密度增加的形式沉积。我们讨论了草本植物沉积 Si 的方式如何影响其抗食草动物特性，并考虑了草种之间 Si 基防御分配差异的生态和农业意义。
