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Temperature response of carbon isotope discrimination and mesophyll conductance in tobacco
Author(s) -
EVANS JOHN R.,
VON CAEMMERER SUSANNE
Publication year - 2013
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.1365-3040.2012.02591.x
Subject(s) - photorespiration , carboxylation , partial pressure , conductance , isotopes of carbon , nicotiana tabacum , chemistry , carbon dioxide , respiration , botany , stomatal conductance , analytical chemistry (journal) , photosynthesis , biophysics , biology , biochemistry , environmental chemistry , oxygen , gene , mathematics , organic chemistry , combinatorics , total organic carbon , catalysis
The partial pressure of CO 2 at the sites of carboxylation within chloroplasts depends on the conductance to CO 2 diffusion from intercellular airspace to the sites of carboxylation, termed mesophyll conductance ( g m ). We investigated the temperature response of g m in tobacco ( Nicotiana tabacum ) by combining gas exchange in high light, ambient CO 2 in either 2 or 21% O 2 with carbon isotope measurements using tuneable diode laser spectroscopy. The g m increased linearly with temperature in 2 or 21% O 2 . In 21% O 2 , isotope discrimination associated with g m decreased from 5.0 ± 0.2 to 1.8 ± 0.2‰ as temperature increased from 15 to 40 °C, but the photorespiratory contribution to the isotopic signal is significant. While the fractionation factor for photorespiration ( f = 16.2 ± 0.7‰) was independent of temperature between 20 and 35 °C, discrimination associated with photorespiration increased from 1.1 ± 0.01 to 2.7 ± 0.02‰ from 15 to 40 °C. Other mitochondrial respiration contributed around 0.2 ± 0.03‰. The drawdown in CO 2 partial pressure from ambient air to intercellular airspaces was nearly independent of leaf temperature. By contrast, the increase in g m with increasing leaf temperature resulted in the drawdown in CO 2 partial pressure between intercellular airspaces and the sites of carboxylation decreasing substantially at high temperature.