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Utilization of O 2 in the metabolic optimization of C 4 photosynthesis
Author(s) -
Maroco J. P.,
Edwards M. S. B. Ku G. E. ,
Edwards G. E.
Publication year - 2000
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 - 10.1046/j.1365-3040.2000.00531.x
Subject(s) - photorespiration , c4 photosynthesis , photosynthesis , botany , photosystem ii , vascular bundle , biology
The combined effects of O 2 on net rates of photosynthesis, photosystem II activity, steady‐state pool size of key metabolites of photosynthetic metabolism in the C 4 pathway, C 3 pathway and C 2 photorespiratory cycle and on growth were evaluated in the C 4 species Amaranthus edulis and the C 3 species Flaveria pringlei . Increasing O 2 reduced net CO 2 assimilation in F. pringlei due to an increased flux of C through the photorespiratory pathway. However, in A. edulis increasing O 2 up to 5–10% stimulated photosynthesis. Analysis of the pool size of key metabolites in A. edulis suggests that while there is some O 2 dependent photorespiration, O 2 is required for maximizing C 4 cycle activity to concentrate CO 2 in bundle sheath cells. Therefore, the response of net photosynthesis to O 2 in C 4 plants may result from the balance of these two opposing effects. Under 21 versus 5% O 2 , growth of A. edulis was stimulated about 30% whereas that of F. pringlei was inhibited about 40%.