Intramolecular deuterium distributions and plant growth conditions

This chapter shows the intramolecular deuterium (D) distribution in photosyn-thetic glucose is not constant, and that this distribution depends on growth conditions. The dependence of the deuterium abundance in precipitation on climate parameters is well-established. In spite of this, and in spite of the fact that all hydrogen in organic plant material is derived from water taken up by plants, δD of organic plant material is rarely used for palaeontological studies. Transpirational isotope discrimination causes isotopic heterogeneity of plant water within leaves and between leaves and stem. Isotopic heterogeneity combined with biochemical reactions could cause non-random intramolecular D distributions, even in the absence of isotope effects. In the nuclear magnetic resonance spectrum of a compound like glucose, one resonance line is observed for each carbon-bound hydrogen atom.