PREMISE Quantifying resistance to embolism in woody plants is important for understanding their drought response. Methods to accurately quantify resistance to embolism continue to be debated. METHODS We used a new microCT-based approach that quantifies embolized conduits and also analyzes conductive conduits by using an x-ray-dense, iodine-rich tracer that moves though the vascular system and can easily be observed in microCT images. Many previous microCT studies assumed that all conduits were initially conductive, which may not be the case if there are developing or occluded conduits. We compared microCT results to a standard benchtop dehydration method and a centrifuge method. During dehydration, we measured gas exchange and quantified water potential at mortality. RESULTS Our microCT curves agreed with previously published microCT curves from the same greenhouse-grown cultivar. We found a significant difference in embolism estimates if we assumed that all water-filled conduits were functional rather than only those containing tracer. Embolism estimates from microCT differed from both the benchtop and centrifuge methods. The benchtop and centrifuge methods did not differ from one another. CONCLUSIONS The new microCT method presented here is valuable in sampling species that may contain nonconductive conduits. Disagreement between microCT and two other methods was likely due to differences in the ways they quantify embolism. MicroCT assess the theoretical effect of embolism, whereas benchtop and centrifuge methods directly measure hydraulic conductivity. The theoretical approach does not fully account for the resistances of flow through a complex 3D vascular network.

中文翻译：

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葡萄藤（葡萄、霞多丽）抗旱性的控制因素：应用一种新的显微CT方法来评估功能性栓塞抗性

前提 量化木本植物对栓塞的抵抗力对于了解它们的干旱反应很重要。准确量化对栓塞的抵抗力的方法仍在争论中。方法 我们使用了一种新的基于 microCT 的方法，该方法可以量化栓塞的导管，并通过使用 X 射线密集、富含碘的示踪剂来分析导电导管，该示踪剂在血管系统中移动，并且可以在 microCT 图像中轻松观察到。许多以前的 microCT 研究假设所有导管最初都是导电的，如果导管正在发育或闭塞，情况可能并非如此。我们将 microCT 结果与标准台式脱水方法和离心机方法进行了比较。在脱水期间，我们测量了气体交换并量化了死亡时的水势。结果我们的 microCT 曲线与先前公布的同一温室栽培品种的 microCT 曲线一致。如果我们假设所有充水管道都有效，而不仅仅是那些含有示踪剂的管道，我们就会发现栓塞估计存在显着差异。来自 microCT 的栓塞估计不同于台式和离心机方法。台式方法和离心方法彼此没有区别。结论 这里介绍的新 microCT 方法在采样可能包含非导电导管的物种方面很有价值。microCT 与其他两种方法之间的分歧可能是由于它们量化栓塞的方式不同。MicroCT 评估栓塞的理论影响，而台式和离心机方法直接测量水力传导率。