title: Correlation between lifetime heterogeneity and kinetics heterogeneity during chlorophyll fluorescence induction in leaves: 1. Mono-frequency phase and modulation analysis reveals a conformational change of a PSII pigment complex during the IP thermal phase.
abstract: The relationship between the fluorescence lifetime (tau) and yield (Phi) obtained in phase and modulation fluorometry at 54 MHz during the chlorophyll fluorescence induction in dark-adapted leaves under low actinic light has been investigated. Three typical phases have been identified: (i) linear during the OI photochemical rise, (ii) convex curvature during the subsequent IP thermal rise, and (iii) linear during the PS slow decay. A similar relationship has been obtained in the fluorescence induction for the fluorescence yield measured at 685 nm plotted versus the fluorescence yield measured at 735 nm. A spectrally resolved analysis shows that the curvature of the tau-Phi relationship is not due to chlorophyll fluorescence reabsorption effects. Several other hypotheses are discussed and we conclude that the curvature of the tau-Phi relationship is due to a variable and transitory nonphotochemical quenching. We tentatively propose that this quenching results from a conformational change of a pigment-protein complex of Photosystem II core antenna during the IP phase and could explain both spectral and temporal transitory changes of the fluorescence. A variable blue shift of the 685 nm peak of the fluorescence spectrum during the IP phase has been observed, supporting this hypothesis.
authors.affiliation: Laboratoire pour l'Utilisation du Rayonnement Electromagnétique, Centre Universitaire Paris-Sud, Bat. 209D, 91898 Orsay, France. nicolae.moise@lure.u-psud.fr
authors.forename: Nicolae
authors.initials: N
authors.lastname: Moise
authors.forename: Ismaël
authors.initials: I
authors.lastname: Moya
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D003624:Darkness; D001467:Hordeum / Q000378:metabolism / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D018532:Pisum sativum / Q000378:metabolism / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism* / Q000528:radiation effects*; D027861:Prunus / Q000378:metabolism / Q000528:radiation effects; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000295:instrumentation / Q000379:methods*; D013223:Statistics as Topic; D013696:Temperature; D014026:Nicotiana / Q000378:metabolism / Q000528:radiation effects
chemical_list: D002734:Chlorophyll; D000077194:Chlorophyll A