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PII S0016-7037(01)00567-1 Fractionation of oxygen isotopes by root respiration

Summary: PII S0016-7037(01)00567-1
Fractionation of oxygen isotopes by root respiration:
Implications for the isotopic composition of atmospheric O2
The Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
(Received August 1, 2000; accepted in revised form January 18, 2001)
Abstract--The ratio of 18
O in atmospheric oxygen depends on the isotopic composition of the substrate
water used in photosynthesis and on discrimination against 18
O in respiratory consumption. The current
understanding of the composition of air O2 attributes the magnitude of the respiratory fractionation to
biochemical mechanisms alone. Thus the discrimination against 18
O is assumed as 18 in normal dark
respiration and 25 to 30 in cyanide resistant respiration. Here we report new results on the fractionation
of O2 isotopes in root respiration. The isotopic fractionation was determined from the change in 18
O of air
due to partial uptake by roots in closed containers. The discrimination in these experiments was in the range
of 11.9 to 20.0 with an average of 14.5. This average is significantly less than the known discrimination
in dark respiration. A simple diffusion-respiration model was used to explain the isotopic discrimination in


Source: Alon, Angert - Institute of Earth Sciences, Hebrew University of Jerusalem


Collections: Geosciences