Collaborative Research: Conifer leaf anatomy determines hydraulic functioning

针叶树在全球具有重要的生态和经济意义。由于干旱、火灾和虫害暴发，许多针叶树种最近经历了极端的死亡事件。迫切需要了解针叶树的生理学，尤其是针叶树的针叶--负责碳吸收和调节水分流失的器官。针叶树叶解剖和生理之间的联系有一个有趣的悖论：如此简单、单一的维管系统，它们如何与阔叶树物种竞争或生存在极端环境中？该项目旨在了解针叶解剖如何影响水分运输和光合作用，以及针叶水分运输如何在干旱期间下降。然后，这些信息将被用来开发一个机械模型，以帮助预测森林生产力和死亡率，以应对干旱和其他环境挑战。该项目将为一名博士后研究员、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“树叶里发生了什么？”的研讨会。为了说明细胞水平的修饰如何影响景观过程，将使用从X射线成像生成的3D打印的针叶针叶模型。解剖模型将通过一个网站免费提供，供教师和学生在学校3D打印手持模型，或者作为没有3D打印技术的学校的教材包。针叶树栖息在一些最干燥、最寒冷的栖息地，那里有树木。许多针叶树种受到热浪和干旱的威胁，这些热浪和干旱会导致生理压力，使它们更容易受到害虫和病原体的攻击。虽然大多数针叶树的叶子只有一个为叶子提供水分的叶脉，但在整个针叶树系统发育过程中，叶脉外的内部解剖结构是令人难以置信的多样化的。这种多样性对水运输和碳吸收的影响尚不清楚。这个项目的主要目标是开发一个机械框架，以了解针叶解剖对叶片水力传导性和光合作用能力的影响。这一机制的理解将被用来阐明针叶树如何适应干旱和寒冷的环境，以及在进化历史上如何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射线计算机显微断层扫描)与水力模型和叶片水力传导性的测量相结合，以阐明针叶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.