title: Reduction of molecular gas diffusion through gaskets in leaf gas exchange cuvettes by leaf-mediated pores.
abstract: There is an ongoing debate on how to correct leaf gas exchange measurements for the unavoidable diffusion leakage that occurs when measurements are done in non-ambient CO2 concentrations. In this study, we present a theory on how the CO2 diffusion gradient over the gasket is affected by leaf-mediated pores (LMP) and how LMP reduce diffusive exchange across the gaskets. Recent discussions have so far neglected the processes in the quasi-laminar boundary layer around the gasket. Counter intuitively, LMP reduce the leakage through gaskets, which can be explained by assuming that the boundary layer at the exterior of the cuvette is enriched with air from the inside of the cuvette. The effect can thus be reduced by reducing the boundary layer thickness. The theory clarifies conflicting results from earlier studies. We developed leaf adaptor frames that eliminate LMP during measurements on delicate plant material such as grass leaves with circular cross section, and the effectiveness is shown with respiration measurements on a harp of Deschampsia flexuosa leaves. We conclude that the best solution for measurements with portable photosynthesis systems is to avoid LMP rather than trying to correct for the effects.
authors: Department of Chemical and Biochemical Engineering, Center for Ecosystems and Environmental Sustainability ECO, Technical University of Denmark, DK-2800 Kgs Lyngby, Denmark. kboe@kt.dtu.dk
authors: Kristine S
authors: KS
authors: Boesgaard
authors: Department of Chemical and Biochemical Engineering, Center for Ecosystems and Environmental Sustainability (ECO), Technical University of Denmark, DK-2800 Kgs, Lyngby, Denmark.
authors: Teis N
authors: TN
authors: Mikkelsen
authors: Section for Terrestrial Ecology, Biological Institute, Building 1, Universitetsparken 15, 2100, Copenhagen Ø, Denmark.
authors: Helge
authors: H
authors: Ro-Poulsen
authors: Department of Chemical and Biochemical Engineering, Center for Ecosystems and Environmental Sustainability (ECO), Technical University of Denmark, DK-2800 Kgs, Lyngby, Denmark.
authors: Andreas
authors: A
authors: Ibrom
mesh_terms: D001901:Botany / Q000295:instrumentation / Q000379:methods; D002245:Carbon Dioxide / Q000378:metabolism*; D019069:Cell Respiration; D004058:Diffusion; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide
keywords: CLIMAITE project; CO2 leakage; diffusion leakage; gasket density; leaf adaptor frame (LAF); leaf respiration; portable gas exchange system.