The non-photochemical reduction of plastoquinone in leaves |
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Authors: | Quentin J Groom David M Kramer Antony R Crofts Donald R Ort |
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Institution: | (1) Photosynthesis Research Unit of USDA/ARS, University of Illinois, 61801 Urbana, IL, USA;(2) Division of Biophysics, University of Illinois, 61801 Urbana, IL, USA;(3) Department of Plant Biology, University of Illinois, 61801 Urbana, IL, USA;(4) Department of Plant Biology, University of Illinois, 190 PABL, 1201 W. Gregory Drive, 61801-3838 Urbana, IL, USA |
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Abstract: | Although it is generally assumed that the plastoquinone pool of thylakoid membranes in leaves of higher plants is rapidly oxidized upon darkening, this is often not the case. A multiflash kinetic fluorimeter was used to monitor the redox state of the plastoquinone pool in leaves. It was found that in many species of plants, particularly those using the NAD-malic enzyme C4 system of photosynthesis, the pool actually became more reduced following a light to dark transition. In some Amaranthus species, plastoquinone remained reduced in the dark for several hours. Far red light, which preferentially drives Photosystem I turnover, could effectively oxidize the plastoquinone pool. Plastoquinone was re-reduced in the dark within a few seconds when far red illumination was removed. The underlying mechanism of the dark reduction of the plastoquinone pool is still uncertain but may involve chlororespiratory activity.Abbreviations apparent Fo
observed fluorescence yield after dark adaptation
- Fm
maximum fluorescence when all QA is fully reduced
- Fo
minimum fluorescence yield when QA is fully oxidized and non-photochemical quenching is fully relaxed
- Fs
steady state fluorescence yield
- PPFD
photosynthetic photon flux density
- PQ
plastoquinone
- QA
primary quinone acceptor of the Photosystem II reaction center
- QB
secondary quinone acceptor to the Photosystem II reaction center
- F
Fm minus Fs |
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Keywords: | chlororespiration flash fluorescence photosynthesis |
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