title: Dark-to-light transition in Synechococcus sp. PCC 7942 cells studied by fluorescence kinetics assesses plastoquinone redox poise in the dark and photosystem II fluorescence component and dynamics during state 2 to state 1 transition.
abstract: We investigated the dark-to-light transition in Synechococcus sp. PCC 7942 cells by a detailed analysis of fluorescence transients induced by strong red light. The transients, recorded with high data-acquisition, revealed all the steps of the fast (OJIP; 10(-5)-1 s) and slow phase (PSM(T); 1-10(3) s), kinetically distinguished with precision. Focusing on the OJIP-rise, we show, for the first time, how the variable to initial fluorescence ratio and the relative height of J-level can serve as indexes of the plastoquinone redox poise and the established state in the dark; hence, differences among cyanobacteria can be recognised in a simple way. Applying intermittent illumination (20-s light pulses separated by 10-s dark intervals) to induce dark-to-light transition and analysing the individual transients, we establish a method by which we determine the fluorescence component not originating from photosystem (PS) II and we assess PSII dynamics during state 2 to state 1 transition. The development of photochemical and non-photochemical quenching is also discussed, as well as evidences favouring the mobile antenna model.
authors.affiliation: Ath. Phylactou 3, 1100, Nicosia, Cyprus. tsimicha@spidernet.com.cy
authors.forename: Merope
authors.initials: M
authors.lastname: Tsimilli-Michael
authors.forename: Kostas
authors.initials: K
authors.lastname: Stamatakis
authors.forename: George C
authors.initials: GC
authors.lastname: Papageorgiou
mesh_terms: D004579:Electron Transport / Q000502:physiology*; D005453:Fluorescence; D007700:Kinetics; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000502:physiology*; D010971:Plastoquinone / Q000378:metabolism*; D046940:Synechococcus / Q000145:classification* / Q000502:physiology / Q000528:radiation effects*
chemical_list: D045332:Photosystem II Protein Complex; D010971:Plastoquinone