title: Temperature response of mesophyll conductance in three C4species calculated with two methods:18O discrimination and in vitro Vpmax.
abstract: Mesophyll conductance (gm) is an important factor limiting rates of C3photosynthesis. However, its role in C4photosynthesis is poorly understood because it has been historically difficult to estimate. We use two methods to derive the temperature responses of gmin C4species. The first (Δ18O) combines measurements of gas exchange with models and measurements of18O discrimination. The second method (in vitro Vpmax) derives gmby retrofitting models of C4photosynthesis and13C discrimination with gas exchange, kinetic constants and in vitro Vpmaxmeasurements. The two methods produced similar gmfor Setaria viridis and Zea mays. Additionally, we present the first temperature response (10-40°C) of C4gmin S. viridis, Z. mays and Miscanthus × giganteus. Values for gmat 25°C ranged from 2.90 to 7.85 μmol m-2s-1Pa-1. Our study demonstrated that: the two described methods are suitable to calculate gmin C4species; gmvalues in C4are similar to high-end values reported for C3species; and gmincreases with temperature analogous to reports for C3species and the response is species specific. These results improve our mechanistic understanding of C4photosynthesis.
authors.affiliation: School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA.
authors.forename: Nerea
authors.initials: N
authors.lastname: Ubierna
authors.affiliation: School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Gandin
authors.affiliation: School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA.
authors.forename: Ryan A
authors.initials: RA
authors.lastname: Boyd
authors.affiliation: School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA.
authors.forename: Asaph B
authors.initials: AB
authors.lastname: Cousins
mesh_terms: D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes; D007553:Isotope Labeling / Q000379:methods*; D007700:Kinetics; D058503:Mesophyll Cells / Q000502:physiology*; D010103:Oxygen Isotopes / Q000378:metabolism*; D010788:Photosynthesis; D006109:Poaceae / Q000502:physiology; D013696:Temperature
chemical_list: D002247:Carbon Isotopes; D010103:Oxygen Isotopes; D002244:Carbon
keywords: C4 photosynthesis; Miscanthus × giganteus; Setaria viridis; Zea mays; carbon isotopes; mesophyll conductance; oxygen isotopes; temperature response