Enhancement of chloroplast energization in Chlorella by treatments inactivating the nitrate-reducing system |
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Authors: | Yuri K Chemeris Antoaneta V Popova Pavel S Venediktov |
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Institution: | (1) Biophysics Department, Faculty of Biology, M.V. Lomonosov State University, Lenin Hills, W-234 Moscow, USSR 119899 |
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Abstract: | Inactivation of the nitrate-reducing system in whole cells of Chlorella vulgaris Bejerinck by darkening, nitrogen starvation, ammonium, or cycloheximide brings cells into a state with a high yield of the millisecond-delayed fluorescence of chlorophyll. Activation of this system by illumination, by adding glucose to dark-adapted cells or nitrate to nitrogen-starved cells brings the cells into a low-yield state. The transitions between the lowand high-yield state induced by alternating light and dark periods are suppressed by tungstate and restored by subsequent molybdate addition. The drop in the delayed-fluorescence yield upon activation of the nitrate-reducing system is associated with the decrease of the amplitude of the electrochemical proton gradient across the thylakoid membrane of the chloroplast, as evidenced by the kinetics of the light-induced adsorption changes at 520 nm. The decrease of the proton gradient may be caused by the electron flow diverting from the cyclic path in photosystem I as a result of the activation of the electron transfer from ferredoxin to nitrite.Abbreviation DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea |
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Keywords: | Chlorella Chloroplast energization Fluorescence (delayed) Nitrate-reducing system |
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