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The significance of the kinetic analysis of fluorescence induction in DCMU‐inhibited chloroplasts in terms of photosystem 2 connectivity and heterogeneity
Author(s) -
Hodges M.,
Barber J.
Publication year - 1983
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(83)80961-2
Subject(s) - dcmu , photosystem ii , thylakoid , plastoquinone , fluorescence , p700 , chlorophyll fluorescence , kinetics , chemistry , photochemistry , biophysics , tricine , photosystem i , chloroplast , biology , photosynthesis , biochemistry , physics , quantum mechanics , gene
A study has been made on the slow component (β max ) of chlorophyll fluorescence induction curves exhibited by DCMU‐inhibited pea thylakoids. In the absence of high levels of screening cations, β max is high and the fluorescence yield low, while the addition of K + , Mg 2+ or Tris(ethylenediamine) cobaltic(III) cation (TEC 3+ ) decreases β max and increases fluorescence yield. These changes are inhibited when the thylakoids are fixed with glutaraldehyde. By comparing cation‐ and light‐harvesting chlorophyll a/b ‐protein (LHCP) phosphorylation‐induced changes it can be seen that β max correlates with changes in the overall kinetics of photosystem (PS) 2 photoreduction, as indicated from the normalised area over the induction curve (Anorm). When the plastoquinone (PQ) pool is chemically reduced by dithionite, prior to the initiation of the curve, both F o and F m are increased and the slow component removed. These observations are used to question the concept of two structurally distinct PS2 centres [Arch. Biochem. Biophys. (1978) 190, 523–530] and to discuss the use of β max in monitoring PS2 organisation.