Evolutionary and functional traits of parenchyma in the hydraulic architecture plants

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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.