Significant Difference in Hydrogen Isotope Composition Between Xylem and Tissue Water in Populus Euphratica

• Published in: Plant, cell and environment Vol. 39; no. 8; pp. 1848 - 1857
• Main Authors: Zhao, Liangju, Wang, Lixin, Cernusak, Lucas A., Liu, Xiaohong, Xiao, Honglang, Zhou, Maoxian, Zhang, Shiqiang
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.08.2016
• Subjects: Deuterium - metabolism; drylands; groundwater; Groundwater - chemistry; hydrogen isotope; oxygen isotope; Oxygen Isotopes - analysis; Oxygen Isotopes - metabolism; Plant Roots - metabolism; Populus; Populus - metabolism; Water - metabolism; water source; Xylem - metabolism; xylem sap; oxygen isotope; drylands; xylem sap; groundwater; water source; hydrogen isotope
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12753

Deuterium depletions between stem water and source water have been observed in coastal halophyte plants and in multiple species under greenhouse conditions. However, the location(s) of the isotope fractionation is not clear yet and it is uncertain whether deuterium fractionation appears in other natural environments. In this study, through two extensive field campaigns utilizing a common dryland riparian tree species Populus euphratica Oliv., we showed that no significant δ18O differences were found between water source and various plant components, in accord with previous studies. We also found that no deuterium fractionation occurred during P. euphratica water uptake by comparing the deuterium composition (δD) of groundwater and xylem sap. However, remarkable δD differences (up to 26.4‰) between xylem sap and twig water, root water and core water provided direct evidence that deuterium fractionation occurred between xylem sap and root or stem tissue water. This study indicates that deuterium fractionation could be a common phenomenon in drylands, which has important implications in plant water source identification, palaeoclimate reconstruction based on wood cellulose and evapotranspiration partitioning using δD of stem water. 1. Isotopic fractionations between groundwater, soil water and plant tissue waters are quantified in Populus euphratica, the only tree species living in deserts 2. No oxygen fractionation occurred between source water and plant tissue waters 3. No deuterium fractionation occurred between source water and xylem sap 4. Large deuterium fractionation occurred between source water and plant tissue waters, challenging the commonly accepted idea that isotopic compositions of tissue waters are the same as source water