Integrating physiology, anatomy, and modelling to understand xylem embolism spreading in angiosperms based on gas diffusion kinetics

整合生理学、解剖学和建模，基于气体扩散动力学了解木质部栓塞在被子植物中的传播

• 批准号: 457287575
• 负责人: Professor Dr. Steven Jansen
• 金额: --
• 依托单位: Institut für Systematische Botanik und Ökologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/457287575?language=en
• 关键词: Integrating; physiology; anatomy; modelling; understand

Water flow through plants has utmost importance for the functioning of our biosphere and the human population, but most people would be extremely surprised to hear that the mechanism of water transport in plants is poorly understood. While there is massive evidence for tensile water transport in plants, one of the major shortcomings is the lack of a mechanistic understanding why this transport system is not constantly failing by pulling in large air-bubbles (embolism), which would especially occur during drought stress. A new “pneumatic technique”, which measures the kinetics of pressure change in a partial vacuum, while extracting gas from a cut open xylem tissue, demonstrates that the molar air discharge corresponds to embolism resistance of xylem based on other methods. This method inspired us to investigate gas movement in xylem and dissolved atmospheric gas in xylem sap. By combining pneumatic and hydraulic experiments with anatomical observations and modelling, this proposal will investigate gas transport across water conducting cells of angiosperm wood under different levels of dehydration. Major questions that will be addressed include gas entry into xylem vessels, the potential link between dissolved gas concentrations of xylem sap and embolism formation, and the anatomical features associated with gas movement between porous cell walls of vessels. We expect that gas diffusion is ca. 200 times faster than mass flow because of the porous nature and large surface area of intervessel pit membranes, which represent porous media for water and gas flow. The rate of gas diffusion will depend on the thickness of intervessel pit membranes and the total amount of intervessel pit membrane area, but also on the non-random arrangement of vessels at places that are hydraulically segmented. Moreover, it is hypothesised that embolism formation is not exclusively pressure-driven, but may depend on the dissolved gas concentration of xylem sap, which is more affected by changes in temperature than pressure.Significant progress will be made in understanding gas transport within the three-dimensional vessel network of angiosperms by conducting pneumatic experiments, centrifuge-flow experiments, and visual observation of embolism spreading based on the optical method. The experiments will be complemented with anatomical observations, including transmission electron microscopy of pit membranes, and the development of a gas diffusion model at the pit membrane and vessel level, which will be tested against the experimental data obtained. Based on the long-standing expertise at Ulm on functional xylem anatomy, this innovative project will contribute to our understanding of drought-induced embolism in plant xylem. Output from this project has implications for our understanding of plant water use and plant responses to drought, which is especially relevant given current concerns about climate change.

流经植物的水对我们的生物圈和人类种群的运作极其重要，但如果听到人们对植物中的水传输机制知之甚少，大多数人会感到非常惊讶。虽然有大量证据表明植物体内存在拉伸水分运输，但主要缺陷之一是缺乏对为什么这种运输系统不会因吸入大量气泡(血栓)而不断失灵的机械理解，这种情况在干旱胁迫期间尤其会发生。一种从切开的木质部组织中提取气体时，在部分真空中测量压力变化动力学的新“气动技术”表明，摩尔气体排放与基于其他方法的木质部抗栓塞性相对应。这种方法启发了我们研究木质部中的气体运动和木质部汁液中溶解的大气气体。通过将气动和水力实验与解剖学观察和建模相结合，该方案将研究不同脱水程度下被子植物木材导水细胞中的气体传输。将解决的主要问题包括气体进入木质部导管，木质部汁液中溶解气体浓度与栓塞物形成之间的潜在联系，以及与导管多孔细胞壁之间气体移动相关的解剖特征。我们预计气体扩散的速度大约是质量流的200倍，这是因为血管间孔膜的多孔性和较大的表面积，它代表了水和气体流动的多孔介质。气体扩散的速度将取决于血管间凹陷膜的厚度和血管间凹陷膜的总面积，而且还取决于血管在水力分段的地方的非随机布置。此外，假设栓塞物的形成不完全是由压力驱动的，而可能取决于木质部汁液中溶解气体的浓度，而木质部汁液中溶解气体的浓度受温度变化的影响比压力更大。通过进行气动实验、离心流实验以及基于光学方法的栓塞物扩散的目测，将在理解被子植物三维血管网络中的气体传输方面取得重大进展。这些实验将辅之以解剖学观察，包括坑膜的透射电子显微镜，以及在坑膜和血管一级建立气体扩散模型，并将根据所获得的实验数据进行测试。基于Ulm在功能木质部解剖方面的长期专业知识，这一创新项目将有助于我们对干旱诱导的植物木质部栓塞的理解。该项目的成果对我们理解植物用水和植物对干旱的反应有影响，鉴于目前对气候变化的担忧，这一点尤其相关。