Resolution of components of non-photochemical chlorophyll fluorescence quenching in barley leaves |
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Authors: | Robin G Walters Peter Horton |
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Institution: | (1) Robert Hill Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, S10 2TN Sheffield, UK |
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Abstract: | Non-photochemical chlorophyll fluorescence quenching (qN) in barley leaves has been analysed by monitoring its relaxation in the dark, by applying saturating pulses of light. At least three kinetically distinct phases to qN recovery are observed, which have previously been identified (Quick and Stitt 1989) as being due to high-energy state quenching (fast), excitation energy redistribution due to a state transition (medium) and photoinhibition (slow). However, measurements of chlorophyll fluorescence at 77 K from leaf extracts show that state transitions only occur in low light conditions, whereas the medium component of qN is very large in high light. The source of that part of the medium component not accounted for by a state transition is discussed.Abbreviations ATP
adenosine 5-triphosphate
- DCMU
33,4-dichlorophenyl]-1,1 dimethylurea
- pH
trans-thylakoid pH gradient
- Fo, Fm
room-temperature chlorophyll fluorescence yield with all reaction centres open, closed
- Fv
variable fluorescence = Fm–Fo
- LHC II
Light harvesting complex II
- PS I, PS II
Photosystem I, II
- P700, P680
primary donor in photosystem I, II
- qP
photochemical quenching of variable fluorescence
- qN
non-photochemical quenching of variable fluorescence
- qNe, qNt, qNi
non-photochemical quenching due to high energy state, state transition, photoinhibition
- qNf, qNm, qNs
components of qN relaxing fast, medium, slow
- qr
quenching of r relative to the dark state
- tricine
N-trishydroxymethyl]methylglycine
- r
ratio of fluorescence maximum from photosystem II to that from photosystem I at 77 K |
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Keywords: | high-energy state quenching photoinhibition photosynthesis state transition 77 K fluorescence |
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