Influence of Carbonic Anhydrase Activity in Terrestrial Vegetation on the 18 O Content of Atmospheric CO 2
- 30 March 2001
- journal article
- other
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 291 (5513) , 2584-2587
- https://doi.org/10.1126/science.1056374
Abstract
The oxygen-18 ( 18 O) content of atmospheric carbon dioxide (CO 2 ) is an important indicator of CO 2 uptake on land. It has generally been assumed that during photosynthesis, oxygen in CO 2 reaches isotopic equilibrium with oxygen in 18 O-enriched water in leaves. We show, however, large differences in the activity of carbonic anhydrase (which catalyzes CO 2 hydration and 18 O exchange in leaves) among major plant groups that cause variations in the extent of 18 O equilibrium (θ eq ). A clear distinction in θ eq between C 3 trees and shrubs, and C 4 grasses makes atmospheric C 18 OO a potentially sensitive indicator to changes in C 3 and C 4 productivity. We estimate a global mean θ eq value of ∼0.8, which reasonably reconciles inconsistencies between 18 O budgets of atmospheric O 2 (Dole effect) and CO 2 .Keywords
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