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Effects of intraleaf variations in carbonic anhydrase activity and gas exchange on leaf C 18 OO isoflux in Zea mays
Author(s) -
Affek Hagit P.,
Krisch Maria J.,
Yakir Dan
Publication year - 2006
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2005.01603.x
Subject(s) - carbonic anhydrase , photosynthesis , respiration , chemistry , carbonic acid , carbon dioxide , dry matter , botany , flux (metallurgy) , zea mays , biology , agronomy , enzyme , biochemistry , organic chemistry
Summary• Variation in the C 18 OO content of atmospheric CO 2 (δ 18 O a ) can be used to distinguish photosynthesis from soil respiration, which is based on carbonic anhydrase (CA)‐catalyzed 18 O exchange between CO 2 and 18 O‐enriched leaf water (δ 18 O w ). • Here we tested the hypothesis that mean leaf δ 18 O w and assimilation rates can be used to estimate whole‐leaf C 18 OO flux (isoflux), ignoring intraleaf variations in CA activity and gas exchange parameters. • We observed variations in CA activity along the leaf (> 30% decline from the leaf center toward the leaf ends), which were only partially correlated to those in δ 18 O w (7 to 21‰), δ 18 O and δ 13 C of leaf organic matter (25 to 30‰ and −12.8 to −13.2‰, respectively), and substomatal CO 2 concentrations (intercellular CO 2 concentrations, c i , at the leaf center were ∼40% of those at the leaf tip). • The combined effect of these variations produced a leaf‐integrated isoflux that was different from that predicted based on bulk leaf values. However, because of canceling effects among the influencing parameters, isoflux overestimations were only ∼10%. Conversely, use of measured parameters from a leaf segment could produce large errors in predicting leaf‐integrated C 18 OO fluxes.