On the 16O/18O isotope effect associated with photosynthetic O2 production

2007 ◽  
Vol 34 (11) ◽  
pp. 1049 ◽  
Author(s):  
Guillaume Tcherkez ◽  
Graham D. Farquhar
Keyword(s):  
Oxygen Isotope ◽  
Isotope Effect ◽  
Classical Theory ◽  
Isotope Composition ◽  
Isotope Effects ◽  
Oxygen Isotope Composition ◽  
Source Water ◽  
18O Isotope ◽  
O2 Production

While photosynthetically evolved O2 has been repeatedly shown to have nearly the same oxygen isotope composition as source water so that there is no corresponding 16O/18O isotope effect, some recent 18O-enrichment studies suggest that a large isotope effect may occur, thus feeding a debate in the literature. Here, the classical theory of isotope effects was applied to show that a very small isotope effect is indeed expected during O2 production. Explanations of the conflicting results are briefly discussed.

Oxygen isotope composition of phloem sap in relation to leaf water in Ricinus communis

2003 ◽  
Vol 30 (10) ◽  
pp. 1059 ◽  
Author(s):  
Lucas A. Cernusak ◽  
S. Chin Wong ◽  
Graham D. Farquhar
Keyword(s):  
Oxygen Isotope ◽  
Dry Matter ◽  
Organic Molecules ◽  
Ricinus Communis ◽  
Isotope Composition ◽  
Leaf Water ◽  
Oxygen Isotope Composition ◽  
Source Water ◽  
Phloem Sap ◽  
Site Water

We measured the oxygen isotope composition of both the water and dry matter components of phloem sap exported from photosynthesising Ricinus communis L. leaves. The 18O / 16O composition of exported dry matter matched almost exactly that expected for equilibrium with average lamina leaf water (leaf water exclusive of water associated with primary veins) with an isotope effect of αo=1.027, where αo=Ro / Rw , and Ro and Rw are 18O / 16O of organic molecules and water, respectively. Average lamina leaf water was enriched by 14–22‰ compared with source water under our experimental conditions, and depleted by 4–7‰, compared with evaporative site water. This showed that it is the average lamina leaf water 18O / 16O signal that is exported from photosynthesising leaves rather than a signal more closely related to that of evaporative site water or source water. Additionally, we found that water exported in phloem sap from photosynthesising leaves was enriched compared with source water; the mean phloem water enrichment observed for leaf petioles was 4.0 ± 1.5‰ (mean ± 1 s.d., n = 27). Phloem water collected from stem bases was also enriched compared with source water. However, the enrichment was approximately 0.8 times that observed for leaf petioles, suggesting some mixing between enriched phloem water and unenriched xylem water occurred during translocation. Results validated the assumption that organic molecules exported from photosynthesising leaves are enriched by 27‰ compared with average lamina leaf water. Furthermore, results suggest that the potential influence of enriched phloem water should be considered when interpreting the 18O / 16O signatures of plant organic material and plant cellulose.

Oxygen isotope composition of Holocene dolomite formed in a humid hypersaline setting: Comment and Reply

Geology ◽  
1993 ◽  
Vol 21 (3) ◽  
pp. 281 ◽  
Author(s):  
Gerald M. Friedman ◽  
R. P. Major ◽  
R. Michael Lloyd ◽  
F. Jerry Lucia
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Oxygen Isotope Composition

scholarly journals Nitrogen isotope effects can be used to diagnose N transformations in wastewater anammox systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paul M. Magyar ◽  
Damian Hausherr ◽  
Robert Niederdorfer ◽  
Nicolas Stöcklin ◽  
Jing Wei ◽  
...  
Keyword(s):  
Isotope Effect ◽  
Isotope Composition ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Anammox Bacteria ◽  
Ammonium Oxidation ◽  
Experimental Conditions ◽  
N Transformations ◽  
Natural Systems ◽  
Inverse Isotope Effect

AbstractAnaerobic ammonium oxidation (anammox) plays an important role in aquatic systems as a sink of bioavailable nitrogen (N), and in engineered processes by removing ammonium from wastewater. The isotope effects anammox imparts in the N isotope signatures (15N/14N) of ammonium, nitrite, and nitrate can be used to estimate its role in environmental settings, to describe physiological and ecological variations in the anammox process, and possibly to optimize anammox-based wastewater treatment. We measured the stable N-isotope composition of ammonium, nitrite, and nitrate in wastewater cultivations of anammox bacteria. We find that the N isotope enrichment factor 15ε for the reduction of nitrite to N2 is consistent across all experimental conditions (13.5‰ ± 3.7‰), suggesting it reflects the composition of the anammox bacteria community. Values of 15ε for the oxidation of nitrite to nitrate (inverse isotope effect, − 16 to − 43‰) and for the reduction of ammonium to N2 (normal isotope effect, 19–32‰) are more variable, and likely controlled by experimental conditions. We argue that the variations in the isotope effects can be tied to the metabolism and physiology of anammox bacteria, and that the broad range of isotope effects observed for anammox introduces complications for analyzing N-isotope mass balances in natural systems.

Stable Hydrogen and Oxygen Isotope Composition of Waters from Mine Tailings in Different Climatic Environments

2007 ◽  
Vol 41 (6) ◽  
pp. 1870-1876 ◽  
Author(s):  
Jorge E. Spangenberg ◽  
Bernhard Dold ◽  
Marie-Louise Vogt ◽  
Hans-Rudolf Pfeifer
Keyword(s):  
Oxygen Isotope ◽  
Mine Tailings ◽  
Isotope Composition ◽  
Oxygen Isotope Composition ◽  
Hydrogen And Oxygen Isotope

Oxygen isotope composition of kaolinite rocks as an indicator of different stages of their lithogenesis

2011 ◽  
Vol 438 (1) ◽  
pp. 697-700
Author(s):  
N. S. Bortnikov ◽  
V. M. Novikov ◽  
E. O. Dubinina ◽  
A. D. Savko ◽  
A. G. Berketa ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Oxygen Isotope Composition
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