Improved method for measuring the apparent CO2 photocompensation point resolves the impact of multiple internal conductances to CO2 to net gas exchange.
There is a growing interest in accurate and comparable measurements of the CO2 photocompensation point (Γ*), a vital parameter to model leaf photosynthesis. The Γ* is measured as the common intersection of several CO2 response curves, but this method may incorrectly estimate Γ* by using linear fits to extrapolate curvilinear responses and single conductances to convert intercellular photocompensation points (Ci *) to chloroplastic Γ*. To determine the magnitude and minimize the impact of these artefacts on Γ* determinations, we used a combination of meta-analysis, modelling and original measurements to develop a framework to accurately determine Ci *. Our modelling indicated that the impact of using linear fits could be minimized based on the measurement CO2 range. We also propose a novel method of analysing common intersection measurements using slope-intercept regression. Our modelling indicated that slope-intercept regression is a robust analytical tool that can help determine if a measurement is biased because of multiple internal conductances to CO2 . Application of slope-intercept regression to Nicotiana tabacum and Glycine max revealed that multiple conductances likely have little impact to Ci * measurements in these species. These findings present a robust and easy to apply protocol to help resolve key questions concerning CO2 conductance through leaves.
Global Change and Photosynthesis Research Unit, USDA/ARS, Urbana, IL, 61801, USA.|Institute of Genomic Biology, University of Illinois, Urbana, IL, 61801, USA.
Berkley J
BJ
Walker
Global Change and Photosynthesis Research Unit, USDA/ARS, Urbana, IL, 61801, USA.|Institute of Genomic Biology, University of Illinois, Urbana, IL, 61801, USA.|Department of Plant Biology, University of Illinois, Urbana, IL, 61801, USA.
Donald R
DR
Ort
D002245:Carbon Dioxide / Q000378:metabolism*; D019069:Cell Respiration; D008954:Models, Biological; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D013025:Glycine max / Q000378:metabolism* / Q000502:physiology; D014026:Nicotiana / Q000378:metabolism* / Q000502:physiology
D002245:Carbon Dioxide
photorespiration; photosynthesis