title: On the polyphasic quenching kinetics of chlorophyll a fluorescence in algae after light pulses of variable length.
abstract: This study reports on kinetics of the fluorescence decay in a suspension of the alga Scenedesmus quadricauda after actinic illumination. These are monitored as the variable fluorescence signal in the dark following light pulses of variable intensity and duration. The decay reflects the restoration of chlorophyll fluorescence quenching of the photosystem II (PSII) antennas and shows a polyphasic pattern which suggests the involvement of different processes. The overall quenching curve after a fluorescence-saturating pulse (SP) of 250-ms duration, commonly used in pulse amplitude modulation applications as the tool for estimating the maximal fluorescence (F m), has been termed P-O, in which P and O have the same meaning as used in the OJIP induction curve in the light. Deconvolution of this signal shows at least three distinguishable exponential phases with reciprocal rate constants of the order of 10, 10(2), and 10(3) ms. The size of the long (>10(3) ms) and moderate (~10(2) ms) lasting components relative to the complete quenching signal after an SP increases with the duration of the actinic pulse concomitantly with an increase in the reciprocal rate constants of the fast (~10 ms) and moderate quenching phases. Fluorescence responses upon single turnover flashes of 30-μs duration (STFs) given at discrete times during the P-O quenching were used as tools for identifying the quencher involved in the P-O quenching phase preceding the STF excitation. Results are difficult to interpret in terms of a single-hit two-state trapping mechanism with distinguishable quenching properties of open and closed reaction centers only. They give support for an earlier hypothesis on a double-hit three-state trapping mechanism in which the so-called semi-closed reaction centers of PSII are considered. In these trapping-competent centers the single reduced acceptor pair [PheQ A](1-), depending on the size of photoelectrochemically induced pH effects on the Q B-binding site, functions as an efficient fluorescence quencher.
authors.affiliation: Department of Plant Physiology, Wageningen University and Research, Wageningen, The Netherlands, wim.vredenberg@wur.nl.
authors.forename: Wim
authors.initials: W
authors.lastname: Vredenberg
authors.forename: Ondrej
authors.initials: O
authors.lastname: Prasil
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D003624:Darkness; D004237:Diuron / Q000378:metabolism; D007700:Kinetics; D008027:Light; D055668:Photochemical Processes / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism; D044444:Scenedesmus / Q000378:metabolism* / Q000528:radiation effects*; D013050:Spectrometry, Fluorescence
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D004237:Diuron; D000077194:Chlorophyll A
references.citation: Planta. 2005 Dec;223(1):114-133
references.pmid: 16411287
references.citation: Biochim Biophys Acta. 2006 Mar;1757(3):173-81
references.pmid: 16569395
references.citation: Photosynth Res. 2009 Aug-Sep;101(2-3):217-32
references.pmid: 19548111
references.citation: Photosynth Res. 2004 Feb;79(2):209
references.pmid: 16228395
references.citation: Photosynth Res. 2013 Oct;116(2-3):189-214
references.pmid: 23794168
references.citation: Photosynth Res. 2012 Sep;113(1-3):15-61
references.pmid: 22810945
references.citation: Plant Physiol. 1989 Jun;90(2):765-72
references.pmid: 16666841
references.citation: Photosynth Res. 2008 Apr;96(1):83-97
references.pmid: 18197465
references.citation: Photosynth Res. 1993 Mar;35(3):323-43
references.pmid: 24318762
references.citation: Biochim Biophys Acta. 2011 Sep;1807(9):1032-43
references.pmid: 21669182
references.citation: J Plant Physiol. 2013 Feb 15;170(3):242-50
references.pmid: 23177088
references.citation: J Photochem Photobiol B. 2012 Feb 6;107:45-54
references.pmid: 22206611
references.citation: Proc Natl Acad Sci U S A. 1972 Nov;69(11):3420-2
references.pmid: 16592030
references.citation: Biophys J. 2000 Jul;79(1):26-38
references.pmid: 10866935
references.citation: Photosynth Res. 2012 Dec;114(2):69-96
references.pmid: 23065335
references.citation: Photosynth Res. 2007 Nov-Dec;94(2-3):275-90
references.pmid: 17665151
references.citation: Photosynth Res. 2007 Jul-Sep;93(1-3):183-92
references.pmid: 17486427
references.citation: Photosynth Res. 2014 May;120(1-2):43-58
references.pmid: 23456268
references.citation: FEBS Lett. 1996 Nov 18;397(2-3):131-5
references.pmid: 8955332
references.citation: Proc Natl Acad Sci U S A. 1972 Jun;69(6):1358-62
references.pmid: 4504343
references.citation: Nature. 1963 Jan 26;197:355-7
references.pmid: 13998015
references.citation: Photosynth Res. 1990 Sep;25(3):147-50
references.pmid: 24420345