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Variations in 13 C discrimination during CO 2 exchange by Picea sitchensis branches in the field
Author(s) -
WINGATE LISA,
SEIBT ULLI,
MONCRIEFF JOHN B.,
JARVIS PAUL G.,
LLOYD JON
Publication year - 2007
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2007.01647.x
Subject(s) - photorespiration , respiration , photosynthesis , dusk , stable isotope ratio , isotope , chemistry , botany , atmospheric sciences , analytical chemistry (journal) , physics , ecology , biology , environmental chemistry , nuclear physics
We report diurnal variations in 13 C discrimination ( 13 Δ) of Picea sitchensis (Bong.) Carr. branches measured in the field using a branch chamber technique. The observations were compared to predicted 13 Δ based on concurrent measurements of branch gas exchange. Observed 13 Δ values were described well by the classical model of 13 Δ including isotope effects during photorespiration, day respiration and CO 2 transfer through a series of resistances to the sites of carboxylation. A simplified linear of model 13 Δ did not capture the observed diurnal variability. At dawn and dusk, we measured very high 13 Δ values that were not predicted by either of the said models. Exploring the sensitivity of 13 Δ to possible respiratory isotope effects, we conclude that isotopic disequilibria between the gross fluxes of photosynthesis and day respiration can explain the high observed 13 Δ values during net photosynthetic gas exchange. Based on the classical model, a revised formulation incorporating an isotopically distinct substrate for day respiration was able to account well for the high observed dawn and dusk 13 Δ values.