title: Asymmetrical effects of mesophyll conductance on fundamental photosynthetic parameters and their relationships estimated from leaf gas exchange measurements.
abstract: Worldwide measurements of nearly 130 C3 species covering all major plant functional types are analysed in conjunction with model simulations to determine the effects of mesophyll conductance (g(m)) on photosynthetic parameters and their relationships estimated from A/Ci curves. We find that an assumption of infinite g(m) results in up to 75% underestimation for maximum carboxylation rate V(cmax), 60% for maximum electron transport rate J(max), and 40% for triose phosphate utilization rate T(u) . V(cmax) is most sensitive, J(max) is less sensitive, and T(u) has the least sensitivity to the variation of g(m). Because of this asymmetrical effect of g(m), the ratios of J(max) to V(cmax), T(u) to V(cmax) and T(u) to J(max) are all overestimated. An infinite g(m) assumption also limits the freedom of variation of estimated parameters and artificially constrains parameter relationships to stronger shapes. These findings suggest the importance of quantifying g(m) for understanding in situ photosynthetic machinery functioning. We show that a nonzero resistance to CO2 movement in chloroplasts has small effects on estimated parameters. A non-linear function with gm as input is developed to convert the parameters estimated under an assumption of infinite gm to proper values. This function will facilitate gm representation in global carbon cycle models.
authors.affiliation: Department of Geological Sciences, University of Texas at Austin, 1 University Station #C9000, Austin, TX, 78712, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Sun
authors.forename: Lianhong
authors.initials: L
authors.lastname: Gu
authors.forename: Robert E
authors.initials: RE
authors.lastname: Dickinson
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Pallardy
authors.forename: John
authors.initials: J
authors.lastname: Baker
authors.forename: Yonghui
authors.initials: Y
authors.lastname: Cao
authors.forename: Fábio Murilo
authors.initials: FM
authors.lastname: DaMatta
authors.forename: Xuejun
authors.initials: X
authors.lastname: Dong
authors.forename: David
authors.initials: D
authors.lastname: Ellsworth
authors.forename: Davina
authors.initials: D
authors.lastname: Van Goethem
authors.forename: Anna M
authors.initials: AM
authors.lastname: Jensen
authors.forename: Beverly E
authors.initials: BE
authors.lastname: Law
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Loos
authors.forename: Samuel C Vitor
authors.initials: SC
authors.lastname: Martins
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Norby
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Warren
authors.forename: David
authors.initials: D
authors.lastname: Weston
authors.forename: Klaus
authors.initials: K
authors.lastname: Winter
mesh_terms: D003198:Computer Simulation; D004579:Electron Transport; D005740:Gases / Q000378:metabolism*; D007700:Kinetics; D058503:Mesophyll Cells / Q000502:physiology*; D010710:Phosphates / Q000378:metabolism; D010788:Photosynthesis
chemical_list: D005740:Gases; D010710:Phosphates
keywords: A/Ci curves; LeafWeb; carbon cycle model; leaf photosynthesis; parameter estimation