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13 CO 2 / 12 CO 2 exchange fluxes in a clamp‐on leaf cuvette: disentangling artefacts and flux components
Author(s) -
Gong Xiao Ying,
Schäufele Rudi,
Feneis Wolfgang,
Schnyder Hans
Publication year - 2015
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/pce.12564
Subject(s) - cuvette , photosynthesis , respiration , flux (metallurgy) , chemistry , analytical chemistry (journal) , carbon dioxide , isotopes of carbon , botany , physics , environmental chemistry , optics , biology , organic chemistry , total organic carbon , biochemistry
Leaks and isotopic disequilibria represent potential errors and artefacts during combined measurements of gas exchange and carbon isotope discrimination (Δ). This paper presents new protocols to quantify, minimize, and correct such phenomena. We performed experiments with gradients of CO 2 concentration (up to ±250 μ mol mol −1 ) and δ 13 C CO2 (34‰), between a clamp‐on leaf cuvette ( LI ‐6400) and surrounding air, to assess (1) leak coefficients for CO 2 , 12 CO 2 , and 13 CO 2 with the empty cuvette and with intact leaves of H olcus lanatus ( C 3 ) or S orghum bicolor ( C 4 ) in the cuvette; and (2) isotopic disequilibria between net photosynthesis and dark respiration in light. Leak coefficients were virtually identical for 12 CO 2 and 13 CO 2 , but ∼8 times higher with leaves in the cuvette. Leaks generated errors on Δ up to 6‰ for H . lanatus and 2‰ for S . bicolor in full light; isotopic disequilibria produced similar variation of Δ. Leak errors in Δ in darkness were much larger due to small biological : leak flux ratios. Leak artefacts were fully corrected with leak coefficients determined on the same leaves as Δ measurements. Analysis of isotopic disequilibria enabled partitioning of net photosynthesis and dark respiration, and indicated inhibitions of dark respiration in full light ( H . lanatus : 14%, S . bicolor : 58%).