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.
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.
Moise
Nicolae
N
Laboratoire pour l'Utilisation du Rayonnement Electromagnétique, Centre Universitaire Paris-Sud, Bat. 209D, 91898 Orsay, France. nicolae.moise@lure.u-psud.fr
Moya
Ismaël
I
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
D002734:Chlorophyll; D000077194:Chlorophyll A