Past work shows a significant negative correlation between foliar oregonin concentration and western tent caterpillar (Malacosoma californicum Packard) feeding on red alder (Alnus rubra Bong.). Above an oregonin threshold of 20% leaf dry weight, little feeding by caterpillars is observed. Concentrations of defensive chemicals are influenced by plant genotype, environmental conditions, insect feeding, and the interactions of these factors. Our objective was to measure the effects of nitrogen (N) availability and wounding on foliar oregonin and condensed tannin concentrations in red alder genotypes. One-year-old seedlings from 100 half-sib red alder families were treated with two levels of ammonium nitrate (NH₄NO₃) for two growing seasons in a common garden. In the second year, leaves from 50 families from the fertilization experiment were used in a bioassay feeding experiment to determine the effects of N fertilization and genotype on WTC damage, and to identify a subset of 20 families with a range of damage to analyze for phytochemical composition. In separate experiments, wound-induction treatments were conducted outdoors and, in a greenhouse using the N treated trees in their third and fourth year, respectively. Foliar condensed tannin, oregonin and N concentrations were measured and ranked among the plant genotypes, and between the two N treatments and two wounding treatments. Results showed that oregonin and condensed tannin concentrations varied among the alder genotypes. Leaf N concentration was negatively correlated with concentration of oregonin. Neither of the measured phenolic compounds responded to wounding. The results suggest that red alder foliar oregonin and condensed tannin are likely constitutive defenses that are largely determined by genotype, and that the negative correlation of defense compounds with plant internal N status holds in this N-fixing tree.

过去的工作表明，叶面俄勒冈素浓度与以红桤木 ( Alnus rubra Bong.) 为食的西部帐篷毛虫 ( Malacosoma californicum Packard)之间存在显着的负相关。高于 20% 叶干重的俄勒冈素阈值，很少观察到毛虫的摄食。防御性化学物质的浓度受植物基因型、环境条件、昆虫饲养以及这些因素的相互作用的影响。我们的目标是测量氮 (N) 可用性和伤害对红桤木基因型中叶面俄勒冈素和浓缩单宁浓度的影响。来自 100 个半同胞赤桤科的一岁幼苗用两种水平的硝酸铵 (NH ₄ NO ₃) 在一个公共花园中的两个生长季节。第二年，将来自施肥实验的 50 个科的叶子用于生物测定饲养实验，以确定施氮和基因型对 WTC 损伤的影响，并确定了具有一系列损伤的 20 个科的子集以进行植物化学分析。作品。在单独的实验中，分别在第三年和第四年使用 N 处理过的树木在室外和温室中进行伤口诱导处理。测量了叶面缩合单宁、俄勒冈素和 N 浓度，并在植物基因型之间以及两个 N 处理和两个伤口处理之间进行了排序。结果表明，俄勒冈素和缩合单宁的浓度在桤木基因型之间有所不同。叶氮浓度与俄勒冈素浓度呈负相关。测得的酚类化合物均未对伤口作出反应。结果表明，红桤叶的俄勒冈素和缩合单宁可能是主要由基因型决定的组成性防御，并且防御化合物与植物内部氮状态的负相关在这棵固氮树中成立。