title: Populations of photoinactivated photosystem II reaction centers characterized by chlorophyll a fluorescence lifetime in vivo.
abstract: Photosystem (PS) II centers, which split water into oxygen, protons, and electrons during photosynthesis, require light but are paradoxically inactivated by it. Prolonged light exposure concomitantly decreased both the functional fraction of PSII reaction centers and the integral PSII chlorophyll (Chl) a fluorescence lifetime in leaf segments of Capsicum annuum L. Acceleration of photoinactivation of PSII by a pretreatment with the inhibitors/uncoupler lincomycin, DTT, or nigericin further reduced PSII Chl a fluorescence lifetimes. A global analysis of fluorescence lifetime distributions revealed the presence of at least two distinct populations of photoinactivated PSII centers, one at 1.25 ns, and the other at 0.58 ns. Light treatment first increased the 1.25-ns component, a weak quencher, at the expense of a component at 2.22 ns corresponding to functional PSII centers. The 0.58-ns component, a strong quencher, emerged later than the 1.25-ns component. The strongly quenching PSII reaction centers could serve to avoid further damage to themselves and protect their functional neighbors by acting as strong energy sinks.
authors.affiliation: Photobioenergetics Group, Research School of Biological Sciences, Australian National University, G.P.O. Box 475, Canberra ACT 2601, Australia.
authors.forename: Shizue
authors.initials: S
authors.lastname: Matsubara
authors.forename: Wah Soon
authors.initials: WS
authors.lastname: Chow
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002212:Capsicum / Q000378:metabolism; D002734:Chlorophyll / Q000737:chemistry*; D000077194:Chlorophyll A; D004229:Dithiothreitol / Q000494:pharmacology; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry; D008034:Lincomycin / Q000494:pharmacology; D008856:Microscopy, Fluorescence / Q000379:methods; D008954:Models, Biological; D009550:Nigericin / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D017785:Photons; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011522:Protons; D013696:Temperature; D013997:Time Factors; D024341:Xanthophylls / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D011522:Protons; D024341:Xanthophylls; D002734:Chlorophyll; D008034:Lincomycin; D009550:Nigericin; D010100:Oxygen; D004229:Dithiothreitol; D000077194:Chlorophyll A