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Carbon isotope discrimination in C 3 ‐C 4 intermediates
Author(s) -
CAEMMERER S.
Publication year - 1992
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.1365-3040.1992.tb01656.x
Subject(s) - isotopes of carbon , carbon fixation , rubisco , c4 photosynthesis , isotope , fractionation , photosynthesis , carbon fibers , chemistry , vascular bundle , botany , biology , biochemistry , materials science , chromatography , environmental chemistry , total organic carbon , physics , quantum mechanics , composite number , composite material
Carbon isotope discrimination in C 3 –C 4 intermediates is determined by fractionations during diffusion and the biochemical fractionations occurring during CO 2 fixation. These biochemical fractionations in turn depend on the fractionation by Rubisco in the mesophyll, the amount of CO 2 fixation. These biochemical fractionations in turn depend on the fractionation by Rubisco in the mesophyll, the amount of CO 2 fixation occurring in the bundle sheath, the extent of bundle‐sheath leakiness and the contribution which C 4 ‐cycle activity makes to the CO 2 pool there. In most instances, carbon isotope discrimination in C 3 –C 4 intermediates is C 3 ‐like because only a small fraction of the total carbon fixed is fixed in the bundle sheath. In particular, this must be the case for Flaveria intermediates which initially fix substantial amounts of CO 2 into C 4 ‐acids. In C 3 –C 4 intermediates that refix photorespiratory CO 2 alone, it is possible for carbon isotope discrimination to be greater than in C 3 ‐species, particularly at low CO 2 pressures or at high leaf temperatures. Short‐term measurements of carbon isotope discrimination and gas exchange of leaves can be used to study the photosynthetic pathways of C 3 ‐C 4 intermediates and their hybrids as has recently been done for C 3 and C 4 species.