Photosynthesis isotopic fractionation

Kinetic isotope effects are an important factor in the biology of deuterium. Isotopic fractionation of hydrogen and deuterium in plants occurs in photosynthesis. The lighter isotope is preferentially incorporated from water into carbohydrates and tipids formed by photosynthesis. Hydrogen isotopic fractionation has thus become a valuable tool in the elucidation of plant biosynthetic pathways (42,43). 

Early reviews by O Leary (1981) and Farquhar et al. (1989) have provided the biochemical background of carbon isotope fractionations during photosynthesis, with more recent accounts by Hayes (2001) and Freeman (2001). 

Park R, Epstein S (1960) Carbon isotope fractionation during photosynthesis, Geochim Cosmochim Acta 21 110-126... 

This phenomenon forms the basis for the formulations of Urey (1947) and Bigeleisen and Mayer (1947) for the temperature dependence of isotopic exchange between two molecules. With the nearly simultaneous development of the isotope-ratio mass spectrometer by Nier et al. (1947), the potential for application of stable isotopes was created. Other isotopic fractionation processes are observed in kinetics, diffusion, evaporation-condensation, crystallization, and biology (e.g., photosynthesis, respiration, nitrogen fixation, sulfate reduction, and transpiration). The concomitant isotopic fractionations can also be used to provide details of the relevant process. 

Similar terms can be derived for other flux components based on knowledge of the isotopic composition of the source material (e.g., atmospheric CO2, ocean-surface inorganic carbon, soil organic carbon) and knowledge of the associated, process-based, isotopic fractionation (e.g., sp for photosynthesis, cr for respiration). Note also that terms such as 5a -b Sao in Equation (14) are also approximations of A. ... 

Our current and rather extensive knowledge of C discrimination during photosynthesis is based primarily on the pioneering works of O Leary (1981), Vogel (1980,1993), and Farquhar et al. (1982), and with more recent updates such as Farquhar and Lloyd (1993), Evans et al. (1986), and Lloyd and Farquhar (1994). These works provide similar analytical treatment to isotopic fractionation during photosynthesis but are... 

Vogel J. C. (1993) Variability of carbon isotope fractionation during photosynthesis. In Stable Isotopes and Plant Carbon Water Relations (eds. J. R. Ehleringer, A. E. Hall, and G. D. Farquhar). Academic Press, pp. 29-46. 

Stable isotopes studies. Numerous researchers have taken advantage of the difference in carbon isotope fractionation during photosynthesis of plants with C3 and C4 photosynthetic pathways as a natural tracer to study soil carbon dynamics (Balesdent et al., 1987). If a C3 forest is converted to a C4 pasture or C4 agricultural field, the whole soil carbon turnover time (t) can be calculated as... 

X (Moj/SS). More complicated relationships have also been derived, based on curvefitting the available experimental data on isotopic fractionation as a function of [O2]. 02-dependent isotopic fractionation during photosynthesis has provided the first mathematically robust isotope-driven model of the C-S-O cycle consistent with geologic observations (Berner et al., 2000). Results of this model show that allowing isotope fractionation to respond to changes in ambient O2... 

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