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Interactions between inorganic phosphate (P i ) assimilation, photosynthesis and respiration in the P i ‐limited green alga Selenastrum minutum *
Author(s) -
GAUTHIER D. A.,
TURPIN D. H.
Publication year - 1997
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.1365-3040.1997.d01-6.x
Subject(s) - photosynthesis , respiration , biology , chloroplast , photorespiration , botany , dcmu , biophysics , biochemistry , photosystem ii , gene
Inorganic phosphate (P i )‐limited chemostat cultures of the green alga Selenastrum minutum were employed to investigate interactions between P i assimilation, respiration and photosynthetic processes. Changes in net and gross gas exchange rates indicated that O 2 evolution decreases during photosynthetic P i assimilation. Room temperature and 77K Chi a fluorescence measurements revealed that this photosynthetic suppression is correlated with a transition from state 1 to state 2. Substantial photosynthetic P i uptake rates occur in the presence of DCMU and KCN. Additionally, the cellular ratio of ATP:NADPH increases following P i enrichment, suggesting that the ratio of cyclic to linear electron flow is enhanced in response to the high energy requirements of P i uptake. Net starch degradation was observed during photosynthetic P i assimilation and the cellular pool size of 3‐phosphoglycerate increased; however, gross gas exchange parameters and cellular metabolite pool sizes indicated that mitochondrial respiration plays a smaller role during P i assimilation in the light than it does in the dark. These observations were used to formulate a model depicting possible interactions between photosynthetic electron flow, photosynthetic and respiratory carbon metabolism and metabolite exchange between the chloroplast, cytosol and mitochondrion during photosynthetic P i assimilation.