Photosynthetic CO2 fixation rate is constrained by CO2 diffusion inside leaves from intercellular airspace to the cytoplasm and chloroplasts in species with either C3 or C4 photosynthetic pathway.
By understanding and quantifying these internal diffusion limitations, novel strategies to manipulate and enhance leaf photosynthesis and water use efficiency through genetic engineering can be identified. Stable isotopes of oxygen (18O) and carbon (13C) in CO2 contain important information that can be used to measure CO2 diffusion within leaves. We use tuneable diode laser spectroscopy to examine and quantify internal conductance to CO2 diffusion using concurrent measurements of gas exchange and 13CO2 and/or C18O16O discrimination.
Understanding leaf level processes of 13CO2 and C18O16O is important for the interpretation of isotope signatures of atmospheric CO2 which are being used in carbon source and sink identification for global carbon emission reduction.