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Online CO 2 and H 2 O oxygen isotope fractionation allows estimation of mesophyll conductance in C 4 plants, and reveals that mesophyll conductance decreases as leaves age in both C 4 and C 3 plants
Author(s) -
Barbour Margaret M.,
Evans John R.,
Simonin Kevin A.,
Caemmerer Susanne
Publication year - 2016
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/nph.13830
Subject(s) - conductance , photosynthesis , chloroplast , isotopes of carbon , isotopes of oxygen , isotope , stable isotope ratio , stomatal conductance , oxygen , botany , chemistry , carbon fibers , fractionation , oxygen isotope ratio cycle , biology , analytical chemistry (journal) , environmental chemistry , biochemistry , materials science , chromatography , physics , total organic carbon , nuclear chemistry , gene , organic chemistry , quantum mechanics , composite number , composite material , condensed matter physics
Summary Mesophyll conductance significantly, and variably, limits photosynthesis but we currently have no reliable method of measurement for C 4 plants. An online oxygen isotope technique was developed to allow quantification of mesophyll conductance in C 4 plants and to provide an alternative estimate in C 3 plants. The technique is compared to an established carbon isotope method in three C 3 species. Mesophyll conductance of C 4 species was similar to that in the C 3 species measured, and declined in both C 4 and C 3 species as leaves aged from fully expanded to senescing. In cotton leaves, simultaneous measurement of carbon and oxygen isotope discrimination allowed the partitioning of total conductance to the chloroplasts into cell wall and plasma membrane versus chloroplast membrane components, if CO 2 was assumed to be isotopically equilibrated with cytosolic water, and the partitioning remained stable with leaf age. The oxygen isotope technique allowed estimation of mesophyll conductance in C 4 plants and, when combined with well‐established carbon isotope techniques, may provide additional information on mesophyll conductance in C 3 plants.