Comparative Analysis of Xylem Function

植物的木质部是陆地上最丰富的组织。在所有的血管组织中，它携带的液体-水-最长的距离。它的功能影响着从光合作用、土壤呼吸到天气的一切。本研究的重点是木材功能的两个关键特性：维持负水压而不空化到汽相，并保持最小的摩擦阻力流动。这些特性影响植物的胁迫耐受性和生产力。气穴是由管道之间的阀状“凹坑”失效引起的。该研究将测试基于概率的假设，即随着每个管道的凹坑数量的增加，空化的脆弱性也会增加。测试将涉及空气注入实验和磁共振成像（MRI），以查看完整树木内的脉管系统。“自然实验”将比较显花植物与更古老的植物群，买麻藤，不同的谱系与独特的坑结构。该研究还将评估穿孔板（导管元件之间的接头）对流动阻力的贡献。这些接头已经从高阻力、有坑的端壁发展到与管道一样宽的开口。这一形态梯度的功能特性将记录在开花植物和买麻藤植物的平行谱系中。单导管测量和有限元建模将连接结构的流动阻力。这项研究的结果将填补我们对木材结构的认识与植物在自然和栽培环境中的表现之间的巨大差距。这项研究的更广泛的影响将是图像分析软件的开发，用于从木材的显微图像中快速推断功能特性。这个“结构-功能”索引将免费提供给教育工作者和研究人员。这对于从世界各地机构收藏的大量木材（包括化石）中提取功能数据至关重要。该项目还将涉及培训本科生和研究生以及博士后助理。

Plant xylem, or wood, is the most abundant tissue on land. Of all vascular tissues, it carries the most fluid - water - the longest distances. How it functions influences everything from photosynthesis and soil respiration to the weather. This research focuses on two key properties of wood function: sustaining negative water pressure without cavitating to the vapor phase, and maintaining minimal frictional resistance to flow. These properties influence plant stress tolerance and productivity. Cavitation is caused by failure of valve-like "pits" between conduits. The research will test the probability-based hypothesis that the vulnerability to cavitation increases as the number of pits per conduit increases. Tests will involve air-injection experiments and Magnetic Resonance Imaging (MRI) to view vasculature inside intact trees. "Natural experiments" will compare flowering plants with the more ancient plant group, Gnetophytes, separate lineages with distinct pit structure. The research will also evaluate the contribution of perforation plates, the joints between conduit elements, to flow resistance. These joints have evolved from high-resistance, pitted end-walls, to openings as wide as the conduit. The functional properties of this morphological gradient will be documented in parallel lineages of flowering plants and Gnetophytes. Single-conduit measurements and finite-element modeling will link joint structure to flow resistance. Results of this research will fill the sizable gap between our knowledge of wood structure and the performance of plants in their natural and cultivated environments. Among the broader impacts of this research will be the development of image-analysis software for rapid inference of functional properties from microscopic images of wood. This "structure-function" index will be freely available to educators and researchers. It will be essential for extracting functional data from extensive collections of wood, including fossils, held in institutions around the world. The project will also involve training of undergraduate and graduate students as well as post-doctoral associates.