Siliceous and non-nutritious: nitrogen limitation increases anti-herbivore silicon defenses in a model grass

Silicon (Si) accumulation alleviates a diverse array of environmental stresses in many plants, including conferring physical resistance against insect herbivores. It has been hypothesised that grasses, in particular, utilise ‘low metabolic cost’ Si for structural and defensive roles under nutrient limitation. While carbon (C) concentrations often negatively correlate with Si concentrations, the relationship between nitrogen (N) status and Si is more variable. Moreover, the impacts of N limitation on constitutive physical Si defences (e.g. silica and prickle cells) against herbivores are unknown. We determined how N limitation affected Si deposition in the model grass Brachypodium distachyon and how changes in these constitutive defences impacted insect herbivore (Helicoverpa armigera) growth rates. We used scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry in conjunction with X-ray mapping (XRM) to quantify physical structures on leaves and determine Si depositi...

硅（Si）在多种植物中可缓解多种环境胁迫，包括赋予植物抵御昆虫植食者的物理抗性。已有假说提出，禾本科植物尤其会在养分限制条件下，利用“低代谢成本”的硅发挥结构支撑与防御功能。通常，植物碳（C）浓度与硅浓度呈负相关，但氮（N）营养状态与硅的关联则更为多变。此外，氮限制对组成型物理硅防御（如硅质细胞与刺细胞）抵御植食者的影响尚不明确。本研究探明了氮限制如何影响模式禾本科植物二穗短柄草（Brachypodium distachyon）的硅沉积，以及这些组成型防御的变化如何影响昆虫植食者棉铃虫（Helicoverpa armigera）的生长速率。我们采用扫描电子显微镜（SEM）、能量色散X射线光谱法结合X射线映射（XRM），对叶片表面的物理结构进行定量分析，并确定硅沉积……