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The kinetics of photoinhibition of the photosynthetic apparatus in pea chloroplasts
Author(s) -
BRADBURY M.,
BAKER N. R.
Publication year - 1986
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/1365-3040.ep11611692
Subject(s) - thylakoid , photoinhibition , electron transport chain , quenching (fluorescence) , chloroplast , photochemistry , photosynthesis , chlorophyll fluorescence , biophysics , chemistry , kinetics , fluorescence , electrochemical gradient , quantum yield , photosystem ii , biology , biochemistry , membrane , physics , quantum mechanics , gene
The kinetics of a range of chlorophyll fluorescence parameters, non‐cyclic electron transport and the capacity of the thylakoids to bind Atrazine were examined during photoinhibition treatment of intact pea chloroplasts. Parameters of fluorescence induction of chloroplasts in the presence and absence of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethyl urea at 20 °C and at 77 K were determined. The contributions of photochemical and non‐photochemical quenching processes to the loss of fluorescence during photoinhibitory treatment were assessed. Two distinct phases of photoinhibitory damage were observed. During the initial 5 min period of exposure to light the minimal fluorescence level ( F o ) increased, whilst the maximal fluorescence level ( F P ) decreased, both coupled and uncoupled non‐cyclic electron transport to methyl viologen decreased and the ability to bind Atrazine to the thylakoids decreased. Fluorescence analyses demonstrated that during this period thylakoids were becoming increasingly less efficient at generating and maintaining a transmembrane proton electrochemical gradient. Photoinhibitory damage that occurred at later times between 5 and 20 min was of a very different nature. Both F o and F P declined, a loss of coupled and uncoupled non‐cyclic electron transport was observed together with a loss of the capacity to photo‐oxidize water. However, no further loss of Atrazine‐binding was associated with such changes. A consistent decrease in the quantum yield of non‐cyclic electron transport was also observed throughout photoinhibition treatment. The possibility of two distinct mechanisms of photoinhibitory damage to the photosynthetic apparatus is discussed.