| | 1 | Author
| Z. Naturforsch | Requires cookie* | | | Title
| Redox-State Dependent Changes of Inhibitor-Binding to the Photosystem II Acceptor Complex  | | | | Abstract
| Binding o f radioactively labelled D C M U , ioxynil and terbutryn to spinach chloroplasts is determined following preillum ination by single-turnover, saturating light flashes. W ith all o f the three herbicides binary oscillations o f binding are observed. D ark-adapted sam ples, or those pre illuminated by an even number o f flashes, bind more inhibitor than sam ples preillum inated by an odd number o f flashes. Binding oscillations depend on inhibitor incubation tim e and on the seasonal adaptation o f the plants. The binding kinetics follow ing a single flash display three phases, the last two o f which can be correlated with reoxidation kinetics o f the secondary p h oto system II acceptor Qb, as determined by fluorescence measurem ents. Analysis o f the binding at DCM U concentrations up to 10"7 M free D C M U yields identical binding constants for dark-and flash preilluminated samples, but much less binding sites follow ing one flash. It is concluded that up to 10~7 M free DCM U, centers with bound Q b do not contribute significantly to total binding. Displacement o f Q b from the binding site is half-saturated at about 10-6 M D C M U , as m onitored via fluorescence induction. The data are considered strong support for the Velthuys 'inhibitor-Q i competition model'. | | | |
Reference
| Z. Naturforsch. 39c, 397 (1984); received D ecem ber 1 1983 | | | |
Published
| 1984 | | | |
Keywords
| Inhibitor Binding, Photosystem II, Binary O scillation, Chlorophyll Fluorescence | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0397.pdf | | | | Identifier
| ZNC-1984-39c-0397 | | | | Volume
| 39 | |
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