Aims In plant eco-physiology, less negative (enriched) carbon 13 (13C) in the leaves indicates conditions of reducing leaf gas exchange through stomata, e.g. under drought. In addition, 13C is expected to be less negative in non-photosynthetic tissues as compared with leaves. However, these relationships in δ13C from leaves (photosynthetic organs) to branches, stems and roots (non-photosynthetic organs) are rarely tested across multiple closely related tree species, multiple compartments, or in trees growing under extreme heat and drought. Methods We measured leaf-to-root 13C in three closely related desert acacia species (Acacia tortilis, A. raddiana and A. pachyceras). We measured δ13C in leaf tissues from mature trees in southern Israel. In parallel, a 7-year irrigation experiment with 0.5, 1.0 or 4.0 L day-1was conducted in an experimental orchard. At the end of the experiment, growth parameters and δ13C were measured in leaves, branches, stems and roots. Important Findings The δ13C in leaf tissues sampled from mature trees was ca. -27‰, far more depleted than expected from a desert tree growing in one of the Earth's driest and hottest environments. Across acacia species and compartments, δ13C was not enriched at all irrigation levels (-28‰ to ca. -27‰), confirming our measurements in the mature trees. Among compartments, leaf δ13C was unexpectedly similar to branch and root δ13C, and surprisingly, even less negative than stem δ13C. The highly depleted leaf δ13C suggests that these trees have high stomatal gas exchange, despite growing in extremely dry habitats. The lack of δ13C enrichment in nonphotosynthetic tissues might be related to the seasonal coupling of growth of leaves and heterotrophic tissues.
Bibliographical noteFunding Information:
The project was funded by the Benoziyo Fund for the Advancement of Science; Mr and Mrs Norman Reiser, together with the Weizmann Center for New Scientists; and the Edith & Nathan Goldberg Career Development Chair. D.U. was funded by Ariovich scholarship and by the scholarship of the environmental science school of the Hebrew University. G.W. thanks the Arava Drainage Authority and the Israeli Ministry of Science and Technology (MOST) for their continued support. The study used data available through the TRY initiative on plant traits ( http://www.try-db.org ; data request 8968). The TRY initiative and database is hosted, developed and maintained by J. Kattge and G. Bönisch (Max Planck Institute for Biogeochemistry, Jena, Germany). TRY is currently supported by DIVERSITAS/Future Earth and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig. Acknowledgements
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- Acacia raddiana
- Acacia tortilis
- Stable isotope
- tree drought resistance
- δC enrichment
- delta C-13 enrichment
- stable isotope