Does plant uptake fractionate phosphate oxygen isotopes?

Oxygen stable isotopes of phosphate are used to trace the cycling of this essential nutrient in terrestrial ecosystems, in lakes, and in oceans, and to reconstruct past environments. Many advances have been made in recent years in refining the use of this tracer through a better understanding of the control that different enzymes have on the isotopes ratio.  There is evidence that phosphate uptake by bacteria is associated with isotopic fractionation. However, it is not known if uptake by plants is also associated with isotopic fractionation, and how the fractionation factor varies under different conditions. This research examines the phosphate-bound oxygen isotope fractionation in uptake by the aquatic macrophyte Lemna gibba, with plants exposed to either phosphate-limited or phosphate-replete conditions. The resulting fractionation factors were not significantly different between the two groups with an average (ε ± SE) of -3.9±0.6‰. This value is similar to that obtained for bacterial subjects in previous research (ε = ~-3.5‰), demonstrating that isotopic fractionation in phosphate uptake exist also in plants, and is of a similar magnitude to that in bacteria.