The functional state of the photosynthetic apparatus of Euglena gracilis cells at the mixotrophic cultivation

Abstract

The state of the photosynthetic apparatus and changes in the redox state of a plastoquinone pool (PQP) in mixotrophic cultures of Euglena gracilis grown either photoautotrophically or photoheterotrophically by adding 100 mM ethanol or 100 mM ethanol together with 40 mM glutamate in the media are studied. Dark reduction of PQP, which correlated with the reduction degree of the primary quinone acceptor Q_A, has been studied by the induction of the fluorescence of chlorophyll a. It is shown that, at the dark incubation, the maximum value of chlorophyll fluorescence gradually decreases in mixotrophic cultures of E. gracilis. It has been concluded that the addition of ethanol as a substrate at the mixotrophic cultivation of E. gracilis increased the rate of photosynthetic electron transport in its cells; the dark reduction of PQP was activated after the light incubation of E. gracilis with substrates and accompanied by a decrease in the ability of PS 2 to absorb the light energy.