COLLABORATIVE RESEARCH: Mechanisms for the decline of leaf hydraulic conductance with dehydration, and plant and environment level impacts

在这个项目中，主要植物反应的机制和后果将被越来越多地认识到在细胞、组织和全植物水平的过程中发挥核心作用-叶片水分运输(水力)系统对脱水的脆弱性。同样，将阐明叶片水分运输对气孔控制和城市森林蒸腾的影响，城市森林蒸腾是城市用水的主要组成部分。对于洛杉矶的不同城市树木，该项目将把新的实验和纳米显微镜技术与建模相结合，以确定叶片水力传导性动态变化中的相对作用，这些机制包括叶脉内的空气阻塞、细胞崩溃和膜蛋白(水通道蛋白)活性的变化。其次，该项目将研究克里夫在确定气孔对大气干旱的响应中的作用。将开发一种新的水传输和气体交换系统的计算机模拟模型，该模型将使用来自实验和解剖学分析的数据进行参数化。该模型将预测蒸腾或干旱过程中木质部解剖及其动态对气孔响应的影响。该项目将根据城市树木气体交换反应的实验测量来测试和改进这一模型。第三个目标是将测量和模型与其他功能特性数据相结合，以预测树木的水分利用和水分利用效率，并用城市树木的径流和生长测量来检验这些预测。总体而言，这项研究将在阐明植物水分运输动态和改进城市森林用水量预测方面开辟新的科学基础，特别是对节约水资源至关重要。更广泛的教育影响包括为研究中代表性不足的本科生提供指导计划内的协作数据收集，以提高对城市生态生理学和生态学的参与和欣赏。

In this project,the mechanisms and consequences of a major plant response will be determined that is increasingly recognized to play a central role in processes at cell, tissue and whole-plant level - the vulnerability of the leaf water transport (hydraulic) system to dehydration. Equally, the implications of leaf water transport for stomatal control and urban forest-level transpiration, a major component of city water use, will be clarified. For diverse urban trees in Los Angeles, the project will combine new experimental and nano-microscopy techniques with modeling to determine the relative roles in the dynamics of leaf hydraulic conductance (Kleaf) of mechanisms including air blockage within the leaf veins, cell collapse, and changes in the activity of membrane proteins (aquaporins). Second, the project will study the role of Kleaf in the determination of the stomatal response to atmospheric drought. A novel computer simulation model of the water transport and gas exchange systems will be developed, to be parameterized with data from experiments and from anatomical analyses. This model will predict the effect of xylem anatomy and its dynamics during transpiration or drought on the responses of stomata. The project will test and refine this model against experimental measurements of gas exchange responses for the urban trees. The third objective is to combine the measurements and model with additional functional trait data to predict tree water use and water use efficiency, and to test these predictions with sapflow and growth measurements for urban trees. Overall,this research will break new scientific ground in clarifying the dynamics of plant water transport, and improving prediction of urban forest water use, especially critical for conservation of water resources. The broader educational impacts include collaborative data collection within a mentoring program for under-represented undergraduates in research, to improve participation and appreciation of urban ecophysiology and ecology.