Using the Fractionation of Hydrogen and Carbon Isotopes to Analyse the Mechanisms of the Primary Processes of Photosynthesis

The primary processes of CO2 fixation and reduction in photosynthesis leave their signatures in the isotopic composition of organic matter. Although these signatures are used widely in geochemistry, biology and climatology to infer the dynamics and history of the biosphere, the information they provide about the mechanisms of the processes that produce them has not been exploited fully. We propose to map the underlying biochemistry responsible for fractionation of hydrogen isotopes, to assess its ability to indicate the water relations of plants, and to use carbon-isotope discrimination to probe the catalytic chemistry of the CO2-fixing enzyme, Rubisco.