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Structure and function of bordered pits: new discoveries and impacts on whole‐plant hydraulic function
Author(s) -
Choat Brendan,
Cobb Alexander R.,
Jansen Steven
Publication year - 2008
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2007.02317.x
Subject(s) - xylem , tracheid , hydraulic resistance , water transport , hydraulic conductivity , hydraulics , electrical conduit , porosity , environmental science , soil science , biology , materials science , geology , botany , water flow , soil water , composite material , engineering , mechanics , mechanical engineering , physics , aerospace engineering
Summary Bordered pits are cavities in the lignified cell walls of xylem conduits (vessels and tracheids) that are essential components in the water‐transport system of higher plants. The pit membrane, which lies in the center of each pit, allows water to pass between xylem conduits but limits the spread of embolism and vascular pathogens in the xylem. Averaged across a wide range of species, pits account for > 50% of total xylem hydraulic resistance, indicating that they are an important factor in the overall hydraulic efficiency of plants. The structure of pits varies dramatically across species, with large differences evident in the porosity and thickness of pit membranes. Because greater porosity reduces hydraulic resistance but increases vulnerability to embolism, differences in pit structure are expected to correlate with trade‐offs between efficiency and safety of water transport. However, trade‐offs in hydraulic function are influenced both by pit‐level differences in structure (e.g. average porosity of pit membranes) and by tissue‐level changes in conduit allometry (average length, diameter) and the total surface area of pit membranes that connects vessels. In this review we address the impact of variation in pit structure on water transport in plants from the level of individual pits to the whole plant.ContentsSummary 1 I. Introduction 2 II. The basic structures 2 III. Safety of transport ‐ pits as safety valves 5 IV. Hydraulic resistance of pits and pit membranes ‐ the cost of safety 9 V. Impacts of pit function on whole‐plant hydraulics 14 VI. Future directions 15Acknowledgements 15References 15