Main conclusion

Monoterpenes and phenolics play distinct roles in defending white spruce trees from insect defoliators. Monoterpenes contribute to the toxicity of the foliage, deterring herbivory, whereas phenolics impede budworm growth. This study demonstrates the complex interplay between monoterpenes and phenolics and their collective influence on the defense strategy of white spruce trees against a common insect defoliator.

Abstract

Long-lived coniferous trees display considerable variations in their defensive chemistry. The impact of these defense phenotype variations on insect herbivores of the same species remains to be thoroughly studied, mainly due to challenges in replicating the comprehensive defense profiles of trees under controlled conditions. This study methodically examined the defensive properties of foliar monoterpenes and phenolics across 80 distinct white spruce families. These families were subsequently grouped into two chemotypes based on their foliar monoterpene concentrations. To understand the separate and combined effects of these classes on tree defenses to the eastern spruce budworm, we conducted feeding experiments using actual defense profiles from representative families. Specifically, we assessed budworm response when exposed to substrates amended with phenolics alone or monoterpenes. Our findings indicate that the ratios and amounts of monoterpenes and phenolics present in the white spruce foliage influence the survival of spruce budworms. Phenotypes associated with complete larval mortality exhibited elevated ratios (ranging from 0.4 to 0.6) and concentrations (ranging from 1143 to 1796 ng mg⁻¹) of monoterpenes. Conversely, families characterized by higher phenolic ratios (ranging from 0.62 to 0.77) and lower monoterpene concentrations (ranging from 419 to 985 ng mg⁻¹) were less lethal to the spruce budworm. Both classes of defense compounds contribute significantly to the overall defensive capabilities of white spruce trees. Monoterpenes appear critical in determining the general toxicity of foliage, while phenolics play a role in slowing budworm development, thereby underscoring their collective importance in white spruce defenses.

中文翻译：

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白云杉中两类防御化学物质对抗云杉芽虫的互补作用

主要结论

单萜和酚类化合物在保护白云杉树免受昆虫落叶剂侵害方面发挥着独特的作用。单萜会增加叶子的毒性，阻止草食性动物，而酚类物质会阻碍芽虫的生长。这项研究证明了单萜和酚类化合物之间复杂的相互作用以及它们对白云杉树针对常见昆虫落叶剂的防御策略的集体影响。

抽象的

长寿的针叶树在防御化学方面表现出相当大的变化。这些防御表型变异对同一物种的昆虫食草动物的影响仍有待深入研究，主要是由于在受控条件下复制树木的综合防御特征面临挑战。这项研究系统地研究了 80 个不同白云杉科叶单萜和酚类物质的防御特性。随后根据叶单萜浓度将这些家族分为两种化学型。为了了解这些类别对东部云杉芽虫树木防御的单独和综合影响，我们使用代表性科的实际防御特征进行了喂养实验。具体来说，我们评估了芽虫在暴露于仅用酚类或单萜修饰的基质时的反应。我们的研究结果表明，白云杉叶子中存在的单萜和酚类物质的比例和数量影响云杉芽虫的存活。与幼虫完全死亡率相关的表型表现出较高的单萜比率（范围从0.4至0.6）和浓度（范围从1143至1796 ng mg ^-1）。相反，以较高酚比（范围为0.62至0.77）和较低单萜浓度（范围为419至985 ng mg ^-1）为特征的家族对云杉芽虫的致死性较低。这两类防御化合物对白云杉树的整体防御能力都有显着贡献。单萜在确定叶子的一般毒性方面似乎至关重要，而酚类物质在减缓芽虫发育方面发挥着作用，从而强调了它们在白云杉防御中的集体重要性。