title: A two-dimensional microscale model of gas exchange during photosynthesis in maize (Zea mays L.) leaves.
abstract: CO2 exchange in leaves of maize (Zea mays L.) was examined using a microscale model of combined gas diffusion and C4 photosynthesis kinetics at the leaf tissue level. Based on a generalized scheme of photosynthesis in NADP-malic enzyme type C4 plants, the model accounted for CO2 diffusion in a leaf tissue, CO2 hydration and assimilation in mesophyll cells, CO2 release from decarboxylation of C4 acids, CO2 fixation in bundle sheath cells and CO2 retro-diffusion from bundle sheath cells. The transport equations were solved over a realistic 2-D geometry of the Kranz anatomy obtained from light microscopy images. The predicted responses of photosynthesis rate to changes in ambient CO2 and irradiance compared well with those obtained from gas exchange measurements. A sensitivity analysis showed that the CO2 permeability of the mesophyll-bundle sheath and airspace-mesophyll interfaces strongly affected the rate of photosynthesis and bundle sheath conductance. Carbonic anhydrase influenced the rate of photosynthesis, especially at low intercellular CO2 levels. In addition, the suberin layer at the exposed surface of the bundle sheath cells was found beneficial in reducing the retro-diffusion. The model may serve as a tool to investigate CO2 diffusion further in relation to the Kranz anatomy in C4 plants.
authors.affiliation: BIOSYST-MeBioS, KU Leuven/Flanders Center of Postharvest Technology, Willem de Croylaan 42, B-3001 Leuven, Belgium; Centre for Crop Systems Analysis, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands.
authors.forename: Moges
authors.initials: M
authors.lastname: Retta
authors.affiliation: BIOSYST-MeBioS, KU Leuven/Flanders Center of Postharvest Technology, Willem de Croylaan 42, B-3001 Leuven, Belgium.
authors.forename: Quang Tri
authors.initials: QT
authors.lastname: Ho
authors.affiliation: Centre for Crop Systems Analysis, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands; BioSolar Cells, P.O. Box 98, 6700 AB Wageningen, The Netherlands.
authors.forename: Xinyou
authors.initials: X
authors.lastname: Yin
authors.affiliation: BIOSYST-MeBioS, KU Leuven/Flanders Center of Postharvest Technology, Willem de Croylaan 42, B-3001 Leuven, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Verboven
authors.affiliation: BIOSYST-MeBioS, KU Leuven/Flanders Center of Postharvest Technology, Willem de Croylaan 42, B-3001 Leuven, Belgium; Centre for Crop Systems Analysis, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands; BioSolar Cells, P.O. Box 98, 6700 AB Wageningen, The Netherlands.
authors.forename: Herman N C
authors.initials: HNC
authors.lastname: Berghuijs
authors.affiliation: Centre for Crop Systems Analysis, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands; BioSolar Cells, P.O. Box 98, 6700 AB Wageningen, The Netherlands.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Struik
authors.affiliation: BIOSYST-MeBioS, KU Leuven/Flanders Center of Postharvest Technology, Willem de Croylaan 42, B-3001 Leuven, Belgium. Electronic address: bart.nicolai@biw.kuleuven.be.
authors.forename: Bart M
authors.initials: BM
authors.lastname: Nicolaï
mesh_terms: D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D003198:Computer Simulation; D004058:Diffusion; D058503:Mesophyll Cells / Q000378:metabolism; D008954:Models, Biological; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D058526:Plant Vascular Bundle / Q000378:metabolism; D003313:Zea mays / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide; D002256:Carbonic Anhydrases
keywords: Bundle sheath conductance; C(4) photosynthesis; Carbon concentration mechanism; Gas exchange; Leaf microstructure; Microscale model