The dynamics of embolism formation and repair in xylem conduits: from bubble scale to loss in plant hydraulic transport capacity

木质部导管中栓塞形成和修复的动力学：从气泡规模到植物水力输送能力的损失

• 批准号: 1754893
• 负责人: Jean-Christoph Domec
• 金额: $ 59.78万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1754893&HistoricalAwards=false
• 关键词: dynamics; embolism; formation; repair; xylem

A clear understanding of water usage and resistance to mortality following drought is necessary across tree species. However, despite decades of research, describing plant water movement remains a formidable scientific challenge, and in the absence of this fundamental knowledge, sustainable management of forests will be impossible. All type of plants, including hardwoods and coniferous trees, have core bundles of vascular tissue inside their stems. These circulatory vascular bundles are composed of hollow conduits known as xylem, or wood, that are specialized to transport water efficiently while allowing maximum resistance to drought (hydraulic safety). Sufficient water transport in plants is not guaranteed when water demand increases during hot and dry days. Under those conditions, water in wood becomes highly unstable and trees can die once an air bubble enters and spreads inside those hollow cells. By integrating modelling activities with visual and physiological processes related to air entry and air bubble formation in wood, plant water transport and resistance to drought will be established. The primary impacts of the proposed project will be to advance discovery in the field of water relations and hydraulic architecture of vascular plants by predicting tree mortality following drought, while promoting training for the next generation of scientists and educators. Results from this research can be directly used in future predictions of vegetation responses to climate. The findings here will also be of interest to policy makers, plant breeders and land managers concerned with potential drought impacts on productivity and distributions of certain species.The overall objective of this project is to link the dynamics of embolism formation and removal under tension in xylem of woody plants starting from the bubble scale and integrating the resulting dynamics along individual conduits to arrive at whole-plant vulnerability to cavitation curves. The specific objectives are to 1) measure and model the timescale required for the gas phase induced by cavitation to fully embolize an entire xylem conduit; 2) investigate the conditions under which bubble formation can spread from one conduit to another; 3) investigate the possibility of bubble resorption under tension to occur; and 4) determine the relation between embolism formation and loss of hydraulic conductivity. To achieve the project objectives, a series of science questions will be addressed: Research question 1 (bubble scale): what are the mechanisms and dynamics of embolism formation and removal in a single xylem conduit? What is the time required for a gas bubble to completely fill and to drain a conduit for varying conduit structures and xylem tensions? Research question 2 (conduit connectivity): Is the time needed for the embolism to fill a conduit dependent on conduit size, and the rigidity of the end-wall pit membrane? Research question 3 (Up-scaling to whole-plant): Do the dynamics of bubble formation in a single conduit explain the whole organ vulnerability to embolism curves. The formulation of bubble formation and spread in transpiring plants will represent a major step forward as the theoretical computational methods, and experimental techniques are now ripe for making this progress.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在不同树种中，有必要清楚地了解干旱后的水分利用和对死亡的抵抗力。然而，尽管经过几十年的研究，描述植物水分运动仍然是一项艰巨的科学挑战，如果缺乏这些基础知识，森林的可持续管理将是不可能的。所有类型的植物，包括硬木和针叶树，其茎内都有核心维管组织束。这些循环维管束由被称为木质部或木材的中空导管组成，这种导管专门用于高效地输送水分，同时允许最大限度地抵抗干旱(水力安全)。在炎热和干旱的日子里，当水需求增加时，植物中充足的水分运输得不到保证。在这种情况下，木材中的水变得非常不稳定，一旦气泡进入并在这些中空细胞内扩散，树木可能会死亡。通过将建模活动与与木材中的空气进入和气泡形成有关的视觉和生理过程相结合，将建立植物水分运输和抗旱性。拟议项目的主要影响将是通过预测干旱后的树木死亡，促进在维管植物的水关系和水力结构领域的发现，同时促进对下一代科学家和教育工作者的培训。这项研究的结果可以直接用于未来植被对气候的反应的预测。这一发现也将引起决策者、植物育种者和土地管理者的兴趣，他们关注干旱对某些物种的生产力和分布的潜在影响。该项目的总体目标是从气泡尺度开始，将木本植物木质部在张力下栓子的形成和清除的动力学联系起来，并沿着个别管道整合由此产生的动力学，以得出整个植物对空化曲线的脆弱性。具体目标是：1)测量和模拟空化引起的气相完全堵塞整个木质部导管所需的时间刻度；2)调查气泡形成可以从一个导管扩散到另一个导管的条件；3)调查在张力下发生气泡再吸收的可能性；以及4)确定血栓形成和水力传导性损失之间的关系。为了实现项目目标，将解决一系列科学问题：研究问题1(气泡尺度)：在单个木质部导管中血栓形成和清除的机制和动力学是什么？对于不同的导管结构和木质部张力，气泡完全填充和排出导管所需的时间是多少？研究问题2(导管连通性)：栓塞术填充导管所需的时间取决于导管的大小和末端壁凹坑膜的硬度吗？研究问题3(放大到全植物)：单个管道中气泡形成的动力学是否解释了整个器官对栓塞曲线的脆弱性。蒸腾植物中气泡形成和扩散的公式将代表着理论计算方法向前迈出的重要一步，实验技术现在已经成熟，可以取得这一进展。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Velocity and Temperature Dissimilarity in the Surface Layer Uncovered by the Telegraph Approximation

• DOI: 10.1007/s10546-021-00632-2
• 发表时间: 2021-06
• 期刊: Boundary-Layer Meteorology
• 影响因子: 4.3
• 作者: Kelly Y. Huang;G. Katul;M. Hultmark

Sweeping Effects Modify Taylor’s Frozen Turbulence Hypothesis for Scalars in the Roughness Sublayer

• DOI: 10.1029/2021gl093746
• 发表时间: 2021-10
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: K. Everard;G. Katul;G. Lawrence;A. Christen;M. Parlange

Mesoscale Temporal Wind Variability Biases Global Air–Sea Gas Transfer Velocity of CO2 and Other Slightly Soluble Gases

中尺度时空风变率使全球空气和海水中二氧化碳和其他微溶气体的传输速度产生偏差

• DOI: 10.3390/rs13071328
• 发表时间: 2021
• 期刊: Remote Sensing
• 影响因子: 5
• 作者: Gu, Yuanyuan;Katul, Gabriel G.;Cassar, Nicolas
• 通讯作者: Cassar, Nicolas

Spatiotemporal sensitivity of thermal stress for monitoring canopy hydrological stress in near real-time

• DOI: 10.1016/j.agrformet.2019.02.016
• 发表时间: 2019-05
• 期刊: Agricultural and Forest Meteorology
• 影响因子: 6.2
• 作者: B. Seyednasrollah;J. Domec;J. Clark

Spectral evidence for substrate availability rather than environmental control of methane emissions from a coastal forested wetland

• DOI: 10.1016/j.agrformet.2020.108062
• 发表时间: 2020-09
• 期刊: Agricultural and Forest Meteorology
• 影响因子: 6.2
• 作者: B. Mitra;Kevan J. Minick;G. Miao;J. Domec;Prajaya Prajapati;S. McNulty;G. Sun;J. King;A. Noormets