It was postulated that Si‐mediated plant resistance to herbivory changes with soil water status, increasing when plants are under drought stress. We subjected collard (Brassica oleracea) to such soil variables and assessed plant responses and effects on the leaf‐chewing larvae of Plutella xylostella and the sap‐sucking aphid Brevicoryne brassicae. Silicon accumulated in collard leaves independently of soil water conditions, but it influenced mainly drought‐stressed plants. Silicon suppressed harmful effects of drought on leaf and root length and raised leaf water content and stomatal size to the same conditions of well‐watered plants. Drought stress reduced hemicellulose and cellulose, but Si did not influence them or lignin. Combination of drought and Si increased total and soluble leaf nitrogen. Drought decreased total glucosinolates, but Si increased such defence metabolites to similar concentrations that were found in well‐watered plants. Nutritional changes mediated by drought and Si in fibre, leaf water content, soluble nitrogen and glucosinolates did not increase insect performance in any feeding guild. Instead, caterpillars performed worse in drought‐stressed or Si‐treated collards, mainly in plants under combined conditions. Silicon improved plant resistance to drought and herbivore stresses.

中文翻译：

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土壤硅和干旱胁迫对叶片咀嚼和吸汁昆虫宿主植物化学和超微结构质量的综合影响

据推测，硅介导的植物对草食动物的抗性会随着土壤水分状况的变化而变化，当植物处于干旱胁迫下时会增加。我们对羽衣甘蓝（Brassica oleracea）进行了这样的土壤变量处理，并评估了植物的反应及其对小菜蛾小菜蛾幼虫和吸汁蚜虫Brevicoryne Brassicae的影响。。硅在卷叶中积累的硅与土壤水分条件无关，但主要影响干旱胁迫的植物。硅可以抑制干旱对叶片和根系长度的有害影响，并在相同条件下的水分充足的条件下提高叶片的水分含量和气孔大小。干旱胁迫减少了半纤维素和纤维素，但是硅不影响它们或木质素。干旱和硅的结合增加了总氮和可溶性叶氮。干旱降低了总的芥子油苷含量，但是硅将防御代谢产物的含量提高到了浇水良好的植物中的相似浓度。干旱和硅在纤维，叶片含水量，可溶性氮和芥子油苷中介导的营养变化在任何饲喂行会中均不会增加昆虫的生长能力。代替，在干旱胁迫或经过Si处理的羽衣甘蓝中，毛虫的表现较差，主要是在综合条件下的植物中。硅改善了植物对干旱和草食动物胁迫的抗性。