Biophysical Journal 8: 1299-1315 (1968)
© 1968 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 Papageorgiou, G. Articles by Govindjee, Search for Related Content PubMed PubMed Citation Articles by Papageorgiou, G. Articles by Govindjee,

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

I. Anacystis nidulans

ABSTRACT

he fluorescence yield of chlorophyll a in dark adapted Anacystis nidulans undergoes a slow change with continuous illumination. After the completion of the initial fast transient, the fluorescence yield rises from the level S to a plateau M within a minute, declining only after prolonged illumination. Both normal and 1,1-dimethyl-3(3'4'-dichloro)-phenylurea (DCMU)-poisoned Anacystis are capable of these changes. In normal Anacystis, the slow increase in the fluorescence yield (S M) requires light absorbed in system II while light absorbed in system I is ineffective. In DCMU-poisoned Anacystis, however, these changes are also promoted by light absorbed in system I. Addition of carbonyl cyanide p-trifluoromethoxy phenylhydrazone (FCCP), a photophosphorylation uncoupler acting near the photosynthetic electron transport chain, abolishes the rise from S to M in normal but has no effect in the DCMU-poisoned system. Phlorizin, a phosphorylase inhibitor, has very little effect. These results suggest that the light-induced variation in the fluorescence yield is related to the conformational changes which accompany photophosphorylation. The fluorescence yield of the auxiliary pigment phycocyanin remains constant throughout the interval of the light-induced changes in the fluorescence yield of chlorophyll a. Consequently, the fluorescence spectrum of the alga is variable on continuous illumination.