title: Wind increases leaf water use efficiency.
abstract: A widespread perception is that, with increasing wind speed, transpiration from plant leaves increases. However, evidence suggests that increasing wind speed enhances carbon dioxide (CO2 ) uptake while reducing transpiration because of more efficient convective cooling (under high solar radiation loads). We provide theoretical and experimental evidence that leaf water use efficiency (WUE, carbon uptake per water transpired) commonly increases with increasing wind speed, thus improving plants' ability to conserve water during photosynthesis. Our leaf-scale analysis suggests that the observed global decrease in near-surface wind speeds could have reduced WUE at a magnitude similar to the increase in WUE attributed to global rise in atmospheric CO2 concentrations. However, there is indication that the effect of long-term trends in wind speed on leaf gas exchange may be compensated for by the concurrent reduction in mean leaf sizes. These unintuitive feedbacks between wind, leaf size and water use efficiency call for re-evaluation of the role of wind in plant water relations and potential re-interpretation of temporal and geographic trends in leaf sizes.
authors.affiliation: Department of Environmental Systems Science, ETH Zurich, Zurich, 8092, Switzerland.
authors.forename: Stanislaus J
authors.initials: SJ
authors.lastname: Schymanski
authors.affiliation: Department of Environmental Systems Science, ETH Zurich, Zurich, 8092, Switzerland.
authors.forename: Dani
authors.initials: D
authors.lastname: Or
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D008954:Models, Biological; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism*; D018526:Plant Transpiration; D027843:Vitis; D014867:Water / Q000378:metabolism; D014919:Wind
chemical_list: D014867:Water; D002245:Carbon Dioxide
keywords: gas exchange; global stilling; leaf energy balance; leaf temperature; water use efficiency; wind speed