Correlation between lifetime heterogeneity and kinetics heterogeneity during chlorophyll fluorescence induction in leaves: 2. Multi-frequency phase and modulation analysis evidences a loosely connected PSII pigment-protein complex.
We report the first direct decomposition of the fluorescence lifetime heterogeneity during multiphasic fluorescence induction in dark-adapted leaves by multi-frequency phase and modulation fluorometry (PMF). A very fast component, assigned to photosystem I (PSI), was found to be constant in lifetime and yield, whereas the two slow components, which are strongly affected by the closure of the reaction centers by light, were assigned to PSII. Based on a modified "reversible radical pair" kinetic model with three compartments, we showed that a loosely connected pigment complex, which is assumed to be the CP47 complex, plays a specific role with respect to the structure and function of the PSII: (i) it explains the heterogeneity of PSII fluorescence lifetime as a compartmentation of excitation energy in the antenna, (ii) it is the site of a conformational change in the first second of illumination, and (iii) it is involved in the mechanisms of nonphotochemical quenching (NPQ). On the basis of the multi-frequency PMF analysis, we reconciled two apparently antagonistic aspects of chlorophyll a fluorescence in vivo: it is heterogeneous with respect to the kinetic structure (several lifetime components) and homogeneous with respect to average quantities (quasi-linear mean tau-Phi relationship).
Moise
Nicolae
N
Laboratoire pour l'Utilisation du Rayonnement Electromagnétique, Centre Universitaire Paris-Sud, Bat. 209D, B.P. 34, 91898 Orsay Cedex, France.
Moya
Ismaël
I
D000222:Adaptation, Physiological / Q000502:physiology / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D003624:Darkness; D007700:Kinetics; D008027:Light; D045332:Photosystem II Protein Complex / Q000378:metabolism* / Q000528:radiation effects*; D018515:Plant Leaves / Q000378:metabolism* / Q000528:radiation effects*; D011506:Proteins / 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
D045332:Photosystem II Protein Complex; D011506:Proteins; D002734:Chlorophyll; D000077194:Chlorophyll A