Evolutionary and functional traits of parenchyma in the hydraulic architecture plants

射线和轴向薄壁（RAP）是次生木质部（即木材）的一个组成部分，在植物物种中表现出相当大的解剖差异。到目前为止，生态和功能木材解剖领域的研究大多集中在导水细胞（导管）上，因为它们对植物的水分运输具有直接的重要性，而对RAP的活细胞的研究很少。RAP在结构和功能上与木质部导管相互交织，在木材中具有多种重要功能。本研究旨在解决木本植物中各种RAP模式的系统发育、解剖学和功能意义等基本问题。三个具体目标是：(1)研究RAP在广泛的木本植物（包括被子植物和裸子植物）中的系统发育特征；(2)表征RAP与导管排列和分布的空间分布；(3)探索RAP在栓塞修复中的功能作用，特别是在水力电容和非结构性碳水化合物方面。对全球木质部功能数据集的综合分析将用于涵盖具有不同分类和地理起源的约400种植物的RAP变化。在这一全球尺度的分析之后，我们将对大约20个物种的木材结构进行详细评估，以量化RAP和导管网络之间的接触面积，并使用各种成像技术（包括光学显微镜、电子显微镜和x射线计算机断层扫描）研究细胞间凹坑的超微结构。RAP在栓塞再填充中的作用将在大约20个物种中进行研究，并与申请人正在进行的研究项目相关联。提出的研究将增加我们对木材功能解剖学的认识，这是一个以前被忽视的领域。更好地了解RAP的生物学，特别是植物如何解渴以在干旱诱导的传导细胞栓塞中存活下来，由于植物提供了许多公共、经济和生态效益，因此具有重要的基础意义。该项目的结果也与当前对气候变化和未来植物分布的担忧有关。

Ray and axial parenchyma (RAP) is an integral component of secondary xylem (i.e., wood) exhibiting a considerable anatomical variation across plant species. So far, most research in the field of ecological and functional wood anatomy has been on water conducting cells (conduits) because of their direct importance for water transport in plants, while little attention has been given to the living cells of RAP. RAP is structurally and functionally interwoven with xylem conduits and has several important functions in wood. The proposed research aims to address basic questions concerning the phylogenetic, anatomical and functional significance of various RAP patterns in woody plants. The three specific objectives are (1) to investigate phylogenetic traits of RAP in a broad range of wood plants (including angiosperms and gymnosperms), (2) to characterize the spatial distribution of the RAP in relation to the arrangement and distribution of conduits, and (3) to explore the functional role of RAP in embolism repair, especially with respect to hydraulic capacitance and non-structural carbohydrates.A comprehensive analysis of a global xylem functional dataset will be used to encompass variation in RAP for ca. 400 species with a diverse taxonomic and geographical origin. Following this global-scale analysis, we will conduct a detailed assessment of wood structure in ca. 20 species in order to quantify the area of contact between the RAP and conduit networks and study the ultrastructure of cell-to-cell pits using various imaging techniques (including light microscopy, electron microscopy, and X-ray computed tomography). The role of RAP in embolism refilling will be studied in ca. 20 species and is linked to ongoing research projects by the applicant.The research proposed will increase our knowledge on the functional anatomy of wood in an area that has been previously neglected. A better understanding of the biology of RAP, and especially how plants are able to quench their thirst to survive drought-induced embolism of their conducting cells, is of fundamental importance due to the numerous public, economic, and ecological benefits that plants provide. The outcome of this project is also relevant in light of current concerns about climate change and future plant distribution.