title: [Effect of cations on the quantum yield and the lifetime of the chloroplast fluorescence].
abstract: The interrelationship between the cation-induced fluorescence changes and the state of the photosystem 2 (PS-2) reaction centers for pea chloroplasts and their osmotic fragments was studied. The effects of K+ and Mg2+ on the fluorescence quantum yield (phi f1) under varying light intensities as well as on the fluorescence lifetime (tau f1) in the saturating light were demonstrated. K+ induces the decrease in tau f1; Mg2+ exerts an opposite effect. The effects were more pronounced when the reaction centers of PS-2 were converted into an inactive state by illuminating the sample with a saturating light or by adding DCMU. Under these conditions the cations' effect on tau f1 was accompanied by proportional changes in tau f1. It was concluded that in Mg-deficient chloroplasts an efficient channel of the excitation quenching appears in antenna chlorophyll of PS-2 with the rate constant of 7 . 10(8) s-1. The simultaneous measurements of tau f1 by phase and modulation type techniques allowed to reveal the emission heterogeneity within the nanosecond time interval and the DCMU-sensitive delayed fluorescence with the lifetime exceeding 10(-7) s and the overall quantum yield approximately equal to 2 . 10(-3).
mesh_terms: D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism*; D004237:Diuron / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D010944:Plants; D011188:Potassium / Q000494:pharmacology*; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence
chemical_list: D004237:Diuron; D008274:Magnesium; D011188:Potassium
vernacular_title: Izmeneniia vykhoda i vremeni zhizni fluorestsentsii khloroplastov pod deĭstviem kationov.