New Zealand kauri (Agathis australis) trees are culturally, socially and ecologically significant within northern New Zealand's nutrient‐poor podocarp forest ecosystems. Phytophthora agathidicida is an aggressive oomycete pathogen, capable of killing A. australis across its ecological range, causing the disease known as kauri dieback. The pathogen, like many other forest Phytophthora species, commences as a fine root rot which progresses to collar rot and resinous cankers on the lower trunk. In this study, we investigated the eco‐physiological and fine root responses of kauri to infection by P. agathidicida and tested whether the foliar application of micronutrients (manganese and zinc combined, iron alone, or a trace element mix) affects dieback disease expression. Fortnightly assessments of chlorophyll‐a‐fluorescence were conducted over 12 weeks, and fine root length and tip numbers were recorded at the end of the experiment. None of the micronutrient treatments had a significant physiological effect regardless of pathogen infection. However, contrary to expectations, pathogen infection caused a significant upregulation in photosynthetic activity over time, as the electron transport rate of infected plants was approximately 26% higher than that of control plants at the end of the trial. These results indicate that an increase in the strength of the below‐ground carbon sink through pathogen consumption of labile carbohydrates (sugars), together with pathogen‐induced root damage, triggered upregulation of photosynthesis in the seedlings. Understanding how P. agathidicida infection affects the physiology and resource allocation in kauri is critical to determining the disease aetiology and management options.

中文翻译：

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agathidicida疫霉的早期感染上调了Agathis australis幼苗的光合活性

新西兰贝壳杉（Agathis australis）树木在新西兰北部营养不良的罗汉松森林生态系统中具有重要的文化，社会和生态意义。疫agathidicida是一个积极的卵菌病原体，能够杀死一个。整个生态范围内的 澳大利亚，导致这种疾病，称为贝壳杉死亡。像许多其他森林疫霉菌一样，病原体开始时是细小的根腐病，然后逐渐发展为下层树干上的衣领腐烂和树脂性溃疡。在这项研究中，我们调查了贝壳杉对P感染的生态生理和良好的根响应。 agathidicida并测试了叶面微量营养素（锰和锌的组合，单独的铁或微量元素的混合物）的施用是否会影响致死性疾病的表达。每两周进行一次叶绿素a评估在12周内进行了荧光测试，并在实验结束时记录了良好的根长和叶尖数。无论病原体感染如何，微量营养素处理均无明显的生理作用。然而，与预期相反，病原体感染随着时间的推移引起光合活性的显着上调，因为在试验结束时，被感染植物的电子传输速率比对照植物高约26％。这些结果表明，通过病原体消耗不稳定的碳水化合物（糖）而增加地下碳汇的强度，以及病原体引起的根部损伤，会触发幼苗中光合作用的上调。了解P如何。 agathidicida 感染影响贝壳杉的生理和资源分配，对于确定疾病的病因和管理选择至关重要。