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Compartmental modelling of photorespiration and carbon metabolism of water stressed leaves
Author(s) -
LAWLOR D. W.,
PEARLMAN J. G.
Publication year - 1981
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.1365-3040.1981.tb00833.x
Subject(s) - photorespiration , photosynthesis , carbon fixation , rubisco , pyruvate carboxylase , glycine , flux (metallurgy) , serine , ribulose , chemistry , biochemistry , metabolism , biology , amino acid , enzyme , organic chemistry
Carbon fluxes in photosynthesis and photorespiration of water stressed leaves have been analysed in a steady state model based on the ribulose diphosphate carboxylase (RuDP carboxylase) and RuDP oxygenase enzyme activities and the CO 2 and O 2 concentrations in the leaf. Agreement between predicted and observed photorespiration (Lawlor & Fock, 1975) and C flux in the glycollate pathway is good over much of the range of water stress, but not at severe stress. An alternative source of respiratory CO 2 is suggested to explain the discrepancy. The model suggests that resistance to CO 2 fixation is mainly in the carboxylation reactions, not in CO 2 transport. Using the steady state model, the kinetics of 14 C incorporation into photosynthetic and photorespiratory intermediates are simulated. The predicted rate of 14 C incorporation is faster than observed and delay terms in the model are used to simulate the slow rates of mixing and metabolic reactions. Inactive pools of glycine and serine are suggested to explain the observed specific activities of glycine and serine. Three models of carbon flux between the glycollate pathway, the photosynthetic carbon reduction cycle and sucrose synthesis are considered. The most satisfactory simulation is for glycollate pathway carbon feeding into the PCR cycle pool of 3‐phosphoglyceric acid which provides the carbon for sucrose synthesis. Simulation of the specific activity of CO 2 released in photorespiration suggests that a source of unlabelled carbon may contribute to photorespiration.