Collaborative Research: Testing the Munch Hypothesis: Hydraulics of Phloem Transport in Vines and Trees

项目标题：合作研究：检验蒙克假说：藤本植物和树木韧皮部运输的水力学主要研究人员：霍尔布鲁克、诺埃尔·M和迈克尔·诺布洛赫NSF项目号：1021779和1022106韧皮部是植物将光合作用产物从合成或储存地点运输到呼吸和/或生长利用地点的细胞管道网络，是植物整合光合作用和生长的主要途径。韧皮部的运输被认为是由渗透作用驱动的，但这是否通过连续的细胞质途径发生尚不清楚。在这个项目中，将使用基于解剖学数据的韧皮部运输速率、膨胀压力和水力传导性的测量来研究藤本植物和树木中韧皮部的水力功能。一个主要的目标是确定膨胀压力的梯度是否真正存在，足以驱动以观察到的速率进行运输，从而支持连续细胞内途径的假设；或者，韧皮部可以被分割成离散的单元，溶质被积极地重新加载到其中。这个问题的解决对于理解植物体内碳水化合物运动的水力约束至关重要。鉴于韧皮部在连接光合作用和生长中的核心作用，对韧皮部运输的全面了解对于预测和潜在地改变植物对资源可获得性和/或压力气候条件的反应是至关重要的。这个合作项目将支持研究生和博士后研究员，并将为本科生提供研究机会。将积极招聘妇女和任职人数不足的少数群体担任这些职位。对K-12和公共教育的贡献包括为阿诺德植物园游客中心举办的互动展览，该中心每年接待超过25万名游客，其中包括许多学校团体。此外，一个在线版本将被张贴在植物园的网站上，作为“树木基础”系列的一部分。第二个大幅面图像展览，伴随着教育材料，将在各种公共空间展出，从华盛顿州的普尔曼开始，随后在全州各地展出。

Project Title: Collaborative Research: Testing the Munch Hypothesis: Hydraulics of Phloem Transport in Vines and TreesPrincipal Investigators: Holbrook, Noel M., and Michael KnoblauchNSF Project Numbers: 1021779 and 1022106 The phloem, a network of cellular conduits that allows plants to transport the products of photosynthesis from sites of synthesis or storage to sites of utilization in respiration and/or growth, is the major pathway through which plants integrate photosynthesis and growth. Phloem transport is hypothesized to be driven osmotically, but whether this occurs through a continuous cytoplasmic pathway is unknown. In this project, measurements of phloem transport rates, turgor pressure and hydraulic conductivity based on anatomical data will be used to investigate the hydraulic functioning of phloem in vines and trees. A major goal is to determine if the gradients in turgor pressure sufficient to drive transport at observed rates actually exist, thus supporting the hypothesis of a continuous intracellular pathway; alternatively the phloem could be segmented into discrete units into which solutes are actively re-loaded. Resolution of this issue is critical for understanding the hydraulic constraints underlying the movement of carbohydrates within plants. Given the central role of the phloem in linking photosynthesis and growth, a comprehensive understanding of phloem transport is essential for predicting and potentially modifying how plants respond to altered resource availability and/or stressful climatic conditions.This collaborative project will support both a graduate student and a postdoctoral fellow, and will provide research opportunities for undergraduates. Women and underrepresented minorities will be actively recruited for these positions. Contributions to K-12 and public education include an interactive exhibit for the Arnold Arboretum's visitor center, which receives over 250,000 visitors per year, including many school groups. In addition, an on-line version will be posted on the Arboretum's web site as part of the "Tree Basics" series. A second exhibit of large-format images, accompanied by educational materials, will be displayed in a variety of public spaces, beginning in Pullman, WA and subsequently throughout the state.