Collaborative Research: Conifer leaf anatomy determines hydraulic functioning

针叶树在生态和经济上都具有全球重要性。由于干旱、火灾和虫害爆发，许多针叶树物种最近经历了极端的死亡事件。目前迫切需要了解针叶树的生理，特别是针叶——负责碳吸收和水分流失调节的器官。针叶树的叶片解剖学和生理学之间存在着一个有趣的悖论：有了这样一个简单的单静脉血管系统，它们如何与阔叶植物竞争或在极端环境中生存？本项目旨在了解针叶树叶片解剖对水分输送和光合作用的影响，以及针叶水分输送在干旱期间如何减少。然后，这些信息将用于开发一个机制模型，以帮助预测应对干旱和其他环境挑战的森林生产力和死亡率。该项目将为一名博士后、一名研究生和多名本科生提供培训。此外，与麦考尔户外科学学校合作，五年级和六年级的学生，他们的父母和老师将参加一个名为“叶子内部发生了什么？”为了说明细胞水平的修改如何影响景观过程，将使用x射线成像生成的3d打印针叶树针模型。解剖模型将通过网站免费提供，供教师和学生在学校3D打印手持模型，或作为教学工具包提供给没有3D打印技术的学校。针叶树栖息在有树木的一些最干燥、最寒冷的栖息地。许多针叶树物种受到热浪和干旱的威胁，这些热浪和干旱会引起生理压力，使它们更容易受到害虫和病原体的侵害。尽管大多数针叶树的叶子只有一条为叶子供水的静脉，但在整个针叶树的系统发育中，静脉外的内部解剖结构有着令人难以置信的多样性。这种多样性对水运和碳吸收的影响尚不清楚。该项目的主要目标是建立一个机制框架，以了解针叶树叶片解剖对叶片水力导度和光合能力的影响。这种机制的理解将用于阐明针叶树如何适应干旱和寒冷的环境，并在进化史上成功地与被子植物物种竞争。该项目将结合最先进的三维成像方法（高分辨率x射线计算机微断层扫描）与水力模型和叶片水力导度测量，以阐明针叶树叶片内部解剖对水力功能的影响。

Conifers are globally important, both ecologically and economically. Many conifer species have recently experienced extreme mortality events due to drought, fire and insect outbreaks. There is an urgent need to understand conifer physiology, and especially conifer needles - the organs responsible for carbon uptake and regulation of water loss. Conifers have an intriguing paradox in the link between their leaf anatomy and physiology: with such a simplistic, single-vein vascular system, how can they compete with broadleaf species or inhabit extreme environments? This project aims to understand how conifer leaf anatomy influences water transport and photosynthesis, and how needle water transport declines during drought. This information will then be used to develop a mechanistic model to help predict forest productivity and mortality in response to drought and other environmental challenges. The project will provide training for a postdoctoral researcher, a graduate student, and multiple undergraduate students. Also, in collaboration with the McCall Outdoor Science School, 5th and 6th grade students, their parents and teachers will participate in a workshop called "What happens inside a leaf?" To illustrate how cellular-level modifications can influence landscape processes, 3D-printed conifer needle models generated from X-ray imaging will be used. Anatomical models will be freely available through a website for teachers and students to 3D print hand-held models at schools, or as teaching kits for schools without access to 3D printing technology. Conifers inhabit some of the driest and coldest habitats where trees are found. Many conifer species are threatened by heat waves and droughts that induce physiological stress that can make them more vulnerable to pests and pathogens. Although most conifer leaves have only a single vein supplying water to the leaf, the internal anatomy outside the vein is incredibly diverse across the conifer phylogeny. The impact of this diversity on water transport and carbon uptake is unknown. The primary goal of this project is to develop a mechanistic framework to understand the influence of conifer leaf anatomy on leaf hydraulic conductance and photosynthetic capacity. This mechanistic understanding will be used to illuminate how conifers have adapted to arid and cold environments and have also been able to successfully compete with angiosperm species over evolutionary history. The project will combine state-of the art 3-dimensional imaging methods (high-resolution X-ray computed micro-tomography) with a hydraulic model and measurement of leaf hydraulic conductance to clarify the impact of conifer leaf internal anatomy on hydraulic function.