Biophysical Journal 9: 22-35 (1969)
© 1969 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Munday, J. C. Articles by Govindjee, Search for Related Content PubMed PubMed Citation Articles by Munday, J. C., Jr. Articles by Govindjee,

Light-Induced Changes in the Fluorescence Yield of Chlorophyll a In Vivo

IV. The Effect of Preillumination on the Fluorescence Transient of Chlorella pyrenoidosa

ABSTRACT

The fluorescence transient of Chlorella pyrenoidosa, excited by saturating blue light, has a base level O, hump I, dip D, peak P, and at 1.5 sec a quasi-steady level S (12). With 2 sec exciting exposures and 4 min dark periods, preillumination-1 ( 690 nm, intensities 1-750 ergs/sec-cm² incident), replacing the dark periods, lowers I more effectively than preillumination-2 (650 nm 680 nm) in both aerobic and anaerobic cells. Results indicate that the intersystem electron transport pool A as well as the primary electron acceptor of pigment system II Q (fluorescence quencher) is normally being reduced at I. Preillumination-1 lowers and delays P. Preillumination-2 (absorbed by both pigment systems) also lowers P, but delays P only at low intensity; at high intensity it hastens P. Preillumination-1 raises S while preillumination-2 lowers S. With 30 instead of 2 sec exciting light exposures, preillumination-1 causes a large S increase, and at low intensity a P increase. The S effects seem to be of a long-term nature (26-29) rather than rapid changes in the redox state of Q. As exciting light intensity increases, fluorescence yield at P increases three-fold maximally. The ratio of P (anaerobic) to O (aerobic) is 5.5. These high ratios restrict the Franck-Rosenberg model of photosynthesis (13), which is based on fluorescence yield doubling.