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

在这个项目中，一个主要的植物反应的机制和后果将被确定，它越来越被认为在细胞、组织和整个植物水平的过程中起着核心作用——叶片水分运输（液压）系统对脱水的脆弱性。同样，将澄清叶片水分运输对气孔控制和城市森林水平蒸腾的影响，这是城市用水的一个主要组成部分。对于洛杉矶的各种城市树木，该项目将结合新的实验和纳米显微镜技术与建模，以确定叶片水力传导（Kleaf）动力学机制的相对作用，包括叶脉内的空气堵塞、细胞崩溃和膜蛋白（水通道蛋白）活性的变化。第二，研究Kleaf在确定大气干旱条件下气孔响应中的作用。将开发一种新的水输送和气体交换系统的计算机模拟模型，用实验和解剖分析的数据进行参数化。该模型将预测蒸腾和干旱条件下木质部解剖结构及其动态变化对气孔响应的影响。该项目将根据城市树木气体交换响应的实验测量来测试和完善该模型。第三个目标是将测量和模型与其他功能性状数据相结合，以预测树木的水分利用和水分利用效率，并通过城市树木的树流量和生长测量来验证这些预测。总之，本研究将在阐明植物水分运移动态、改善城市森林水分利用预测方面开辟新的科学领域，对水资源保护具有重要意义。更广泛的教育影响包括在研究中为代表性不足的本科生提供指导计划的协作数据收集，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.