Uncertainty in measurements of the photorespiratory CO(2) compensation point and its impact on models of leaf photosynthesis

Rates of carbon dioxide assimilation through photosynthesis are readily modeled using the Farquhar, von Caemmerer, and Berry (FvCB) model based on the biochemistry of the initial Rubisco-catalyzed reaction of net C(3) photosynthesis. As models of CO(2) assimilation rate are used more broadly for simulating photosynthesis among species and across scales, it is increasingly important that their temperature dependencies are accurately parameterized. A vital component of the FvCB model, the photorespiratory CO(2) compensation point (Γ (*)), combines the biochemistry of Rubisco with the stoichiometry of photorespiratory release of CO(2). This report details a comparison of the temperature response of Γ (*) measured using different techniques in three important model and crop species (Nicotiana tabacum, Triticum aestivum, and Glycine max). We determined that the different Γ (*) determination methods produce different temperature responses in the same species that are large enough to impact higher-scale leaf models of CO(2) assimilation rate. These differences are largest in N. tabacum and could be the result of temperature-dependent increases in the amount of CO(2) lost from photorespiration per Rubisco oxygenation reaction. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11120-017-0369-8) contains supplementary material, which is available to authorized users.