Phloem water isotopically different to xylem water: Potential causes and implications for ecohydrological tracing

Détails

ID Serval
serval:BIB_103C426B8D11
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
Phloem water isotopically different to xylem water: Potential causes and implications for ecohydrological tracing
Périodique
Ecohydrology
Auteur⸱e⸱s
Nehemy Magali F., Benettin Paolo, Allen Scott T., Steppe Kathy, Rinaldo Andrea, Lehmann Marco M., McDonnell Jeffrey J.
ISSN
1936-0584
1936-0592
Statut éditorial
Publié
Date de publication
04/2022
Peer-reviewed
Oui
Volume
15
Numéro
3
Langue
anglais
Résumé
The stable isotopes of hydrogen and oxygen in xylem water are often used to investigate tree water sources. But this traditional approach does not acknowledge the contribution of water stored in the phloem to transpiration and how this may affect xylem water and source water interpretations. Additionally, there is a prevailing assumption that there is no isotope fractionation during tree water transport. Here, we systematically sampled xylem and phloem water at daily and subdaily resolutions in a large lysimeter planted with Salix viminalis. Stem diurnal change in phloem water storage and transpiration rates were also measured. Our results show that phloem water is significantly less enriched in heavy isotopes than xylem water. At subdaily resolution, we observed a larger isotopic difference between xylem and phloem during phloem water refilling and under periods of tree water deficit. These findings contrast with the expectation of heavy-isotope enriched water in phloem due to downward transport of enriched leaf water isotopic signatures. Because of previous evidence of aquaporin mediated phloem and xylem water transport and higher osmotic permeability of lighter hydrogen isotopologues across aquaporins, we propose that radial water transport across the xylem–phloem boundary may drive the relative depletion of heavy isotopes in phloem and their relative enrichment in xylem.
Mots-clé
phloem water, stable isotopes, stem water storage, tree water relations, tree water source, tree water status, xylem water
Web of science
Création de la notice
21/11/2023 18:09
Dernière modification de la notice
02/05/2024 17:08
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