Multi-isotope labelling of organic matter by diffusion of 2H/18O-H2O vapour and 13C-CO2 into the leaves and its distribution within the plant

摘要: Abstract. Isotope labelling is a powerful tool to study elemental cycling within terrestrial ecosystems. Here we describe new multi-isotope technique label organic matter (OM). We exposed poplars (Populus deltoides × nigra) for 14 days an atmosphere enriched in 13CO2 and depleted 2H218O. After 1 week, the water-soluble leaf OM (δ13C = 1346 ± 162‰) water were strongly labelled (δ18O −63 8, δ2H −156 15‰). The isotopic composition was between atmospheric stem water, indicating considerable back-diffusion of vapour into leaves (58–69%) opposite direction net transpiration flow. atomic ratios labels recovered (18O/13C, 2H/13C) 2–4 times higher than stems roots. This could be indication synthesis more condensed compounds roots (e.g. lignin vs. cellulose) or might result O H exchange fractionation processes during phloem transport biosynthesis. demonstrate that three major elements (C, O, H) can traced simultaneously plant. approach interdisciplinary interest fields plant physiology, palaeoclimatic reconstruction soil science.