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Regulation of photosynthetic light harvesting by nitrogen assimilation in the green alga Selenastrum minutum
Author(s) -
Turpin David H.,
Bruce Doug
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)80714-t
Subject(s) - photosynthesis , photosystem ii , electron transport chain , photochemistry , photosystem , assimilation (phonology) , chlorophyll fluorescence , fluorescence , chlorophyll , biology , chlorophyll a , non photochemical quenching , biophysics , chemistry , botany , linguistics , philosophy , physics , quantum mechanics
The interaction of whole cell metabolism with the distribution of excitation energy between photosystem 2 (PS2) and photosystem 1 (PS1), the light state transition, was investigated in vivo in the green alga Selenastrum minutum . Nitrogen limited cells of S. minutum were presented with a pulse of either NH 4 + or NO 3 − in the light. As shown previously, CO 2 fixation is inhibited and high rates of N assimilation ensue [(1986) Plant Physiol. 81, 273–279]. NH 4 + assimilation has a much higher requirement ratio for ATP/NADPH than either CO 2 or NO 3 − assimilation and thus drastically increases the demand for ATP relative to reducing power. Room temperature chlorophyll a fluorescence kinetic measurements showed that a reversible non‐photochemical quenching of PS2 fluorescence accompanied the assimilation of NH 4 + but not the assimilation of NO 3 − or CO 2 . 77K fluorescence emission spectra taken from samples removed at regular intervals during NH + 4 assimilation showed that the non‐photochemical quenching of PS2 was accompanied by a complementary increase in the fluorescence yield of PS1, characteristic of a transition to state 2. Our data suggests that S. minutum responds to the increased demand for ATP/NADPH during NH 4 assimilation by inducing the light state transition to direct more excitation energy to PS1 at the expense of PS2 to increase the production of ATP by cyclic electron transport.