AN030: Rapid analysis of water isotope fractionation along a Pinus spp. branch by IM-CRDS.
Induction Module Cavity Ring-Down Spectroscopy is demonstrated as a rapid and easy method to use water isotopes to probe physiological processes
Stable isotope ratios of hydrogen (2H/1H; δD) and oxygen (18O/16O; δ18O) in water have long been used to probe physiological and ecological processes. However, the analytical methodology required for these measurements (vacuum line extraction followed by isotope ratio mass spectrometry, VLE/IRMS) is expensive, long, and hazardous. Here, Induction Module Cavity Ring-Down Spectroscopy (IM-CRDS) is presented as a simple and rapid alternative to VLE/IRMS. A sample of Pinus spp. was sampled at 1 cm intervals, from branch to leaf tip and the isotopes of water measured. Very little variation along the 7.5 cm length of branch is observed (δD = -55.02 ± 0.98 ‰ and δ18O = -5.06 ± 0.26 ‰), while δD and δ18O are enriched by 75.11 and 27.39 ‰, respectively, from branch to leaf tip. The results are consistent with previous studies which show enhanced deuterium excess due to evapotranspiration. The greatly simplified approach offered by IM-CRDS allowed this data to be collected in about 1.5 hours, and sample prep required only a ruler, razor blade and stainless steel strips. The IM-CRDS opens the possibility of using natural abundance stable isotopes to rapidly probe physiological processes such as stomatal conductance, shifting water source, or label tracing, like never before.