title: Enhancement of chloroplast energization in Chlorella by treatments inactivating the nitrate-reducing system.
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.
authors.affiliation: Biophysics Department, Faculty of Biology, M.V. Lomonosov State University, Lenin Hills, W-234, Moscow, USSR 119899.
authors.forename: Y K
authors.initials: YK
authors.lastname: Chemeris
authors.forename: A V
authors.initials: AV
authors.lastname: Popova
authors.forename: P S
authors.initials: PS
authors.lastname: Venediktov