In wheat chloroplasts, NO2- (5 mM) inhibited non-cyclic phosphorylation coupled to the linear electron flow through both photosystems but stimulated cyclic phosphorylation with phenazine methosulfate (plus diuron) and electron flux from an artificial electron donor through PSI and methylviologen to oxygen. During light energization of chloroplasts, NO2- increased the F740/F695 ratio in the low-temperature fluorescence spectra, thus suggesting that the energy of absorbed quanta is redistributed in favor of PSI. Nitrite also stimulated the activity of Mg2+-dependent H+-ATPase. Changes in the slow component of the induction curve of delayed fluorescence also suggest that NO2- affects energy transformation processes that are coupled to electron transport in the chloroplasts. Nitrite had no effect on these functional characteristics of thylakoids and chloroplasts isolated from plants grown under nitrogen deficiency in the medium.