Effect of Changes in Leaf Water Oxygen Isotopic Composition on Discrimination Against C18O16O During Photosynthetic Gas Exchange
LB Flanagan, SL Phillips, JR Ehleringer, J Lloyd and GD Farquhar
Australian Journal of Plant Physiology
21(2) 221 - 234
Photosynthetic gas exchange measurements were combined with measurements of the carbon and oxygen stable isotopic composition of CO2 after it passed over a leaf of Phaseolus vulgaris or Senecio spp. plants held in a controlled environment chamber. Calculations were then made of discrimination by the leaf against 13CO2 and C18O16O. Leaves were maintained at different vapour pressure gradients in order to generate a range of leaf water 18CO/16CO ratios. The 18CO content of leaf water increased when plants were exposed to higher vapour pressure deficits. The observed C18O16O discrimination values also increased with an increase in the leaf-air vapour pressure gradient and the associated change in leaf water 18/CO16CO values. In addition, the observed C18O16O discrimination values were strongly correlated with values predicted by a mechanistic model of isotopic fractionation.
Full text doi:10.1071/PP9940221
© CSIRO 1994