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Kazuhiko Satoh, Sakae Katoh, Fluorescence Induction in Chloroplasts Isolated from the Green Alga, Bryopsis maxima IV. The I-D Dip, Plant and Cell Physiology, Volume 22, Issue 1, February 1981, Pages 11–21, https://doi.org/10.1093/oxfordjournals.pcp.a076136
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Abstract
Fluorescence induction of intact Bryopsis chloroplasts which previously had been illuminated in the presence of dithionite then kept in the dark prior to measurement showed marked quenching from an intermediary peak I to a lower level D before a secondary rise to a peak P. A small hump (H), related to the membrane potential formed across the thylakoid membranes, overlapped D.
The maximum extent of quenching—the I-D dip—was attained in chloroplasts which had been illuminated for 1 sec prior to dark incubation for 1 min. This illumination caused the complete reduction of secondary electron acceptors and the partial reduction of Q, the primary electron acceptor of photosystem II. Chloroplasts developed the capacity for transient photooxidation of cytochrome f during subsequent dark incubation, indicating that there was dark oxidation of electron acceptors of photosystem I which had been reduced by the illumination. A close correlation was found between the I-D dip and the transient photooxidation of cytochrome f with respect to the kinetics of light induced changes as well as dark restoration after the illumination. Inhibitor studies showed that the dip decreased when the pool size of photosystem I acceptors was reduced. Our results show that the I-D dip and the transient photooxidation of cytochrome f depend upon a common acceptor pool of photosystem I. We concluded that the I-D dip is due to the oxidation of Q by photosystem I with a limited electron acceptor pool.
