[Effect of choline chloride on photosynthetic oxygen release and variable and delayed fluorescence of chlorophyll in Chlamydomonas reinhardtii cells]. / Fotosinteticheskoe vydelenie kisloroda, peremennaia i zamedlennaia fluorestsentsiia khlorofilla kletok Chlamydomonas reinhardtii pri deistvii kholinkhlorida.

The influence of the growth retardant chlorocholine chloride on the rate of photosynthetic oxygen evolution and the induction of chlorophyll fluorescence in unicellular green algae Chlamydomonas was studied depending on concentration and the time of cell growth. It was shown that low concentrations chlorocholine chloride (0.02 g/l) affected insignificantly the photosynthesis and chlorophyll fluorescence. The growth of the culture in the presence of higher chlorocholine chloride concentrations (0.2 and 2 g/l) led to a significant reduction in the rate of oxygen production, and photoinduced changes in chlorophyll fluorescence yield. Young cells were more sensitive to chlorocholine chloride than old cells.

[Effect of high magnesium ion concentration on the electron transport rate and proton exchange in thylakoid membranes in higher plants]. / Vliianie vysokikh kontsentratsii ionov magniia na skorost' élektronnogo transporta i protonnyi obmen v tilakoidnykh membranakh vyshikh rastenii.

The effects of magnesium ion concentration on the rate of electron transport in isolated pea thylakoids were investigated in the pH range from 4.0 up to 8.0. In the absence of magnesium ions in the medium and in the presence of 5 mM MgCl2 in the experiments not only without added artificial acceptors but also with ferricyanide or methylviologen as an acceptor, this rate had a well-expressed maximum at pH 5.0. It was shown that, after depression to minimal values at pH 5.5-6.5, it gradually rose with increasing pH. An increase in magnesium ion concentration up to 20 mM essentially affected the electron transfer rate: it decreased somewhat at pH 4.0-5.0 but increased at higher pH values. At this magnesium ion concentration, the maximum rate was at pH 6.0-6.5 and the minimum, at pH 7.0. Subsequent rise upon increasing pH to 8.0 was expressed more sharply. The influence of high magnesium ion concentration on the rate of electron transport was not observed in the presence of gramicidin D. It was found that without uncoupler, the changes in the electron transfer rate under the influence of magnesium ions correlated to the changes in the first-order rate constant of the proton efflux from thylakoids. It is supposed that the change in the ability of thylakoids to keep protons by the action of magnesium ions is the result of electrostatic interactions of these ions with the charges on the external surface of membranes. A possible role of regulation of the electron transport rate by magnesium ions in vivo is discussed.