Leaf hydraulic design influences the development of isotope gradients in leaves, but are there subsequent effects on isotopes of atmospheric oxygen?

Leaf water becomes enriched in heavier isotopes during transpiration, with the degree of enrichment dependent on evaporative conditions. However, there has been considerable uncertainty regarding the importance of gradients in isotope enrichment within leaves (i.e. a Péclet effect).  That is, experimental studies show that evidence is approximately equally divided between the Péclet effect being important and being irrelevant for leaves. Our recent work demonstrates a link between the hydraulic design of leaves and the presence or otherwise of a Péclet effect.  That is, with prior knowledge of the pathways of water movement through leaves, the most appropriate modelling framework can be selected and uncertainty in interpretation and prediction reduced.

Reducing uncertainty is important because the H₂¹⁸O composition of leaves is passed on to oxygen atoms in O₂ and CO₂ so terrestrial plants strongly influence isotopic composition of the atmosphere. Of particular interest is the interpretation of the Dole effect, the oxygen isotopic imbalance between atmospheric O₂ and seawater.  The ice core record of the Dole effect has been interpreted as an integrative proxy for the global balance between terrestrial and oceanic productivity, or more recently as an indication of the migration of terrestrial productivity towards and away from the equator.  Both interpretations depend on highly uncertain leaf water isotope enrichment models. In light of the link between leaf hydraulic design and the Péclet effect, should we expect differences between species in the ¹⁸O of O₂ produced by photosynthesis?  Do we need to reinterpret the Dole effect?