GROWTH AND PHOTOSYNTHETIC ACTIVITY OF G REE N ALGAE CHLORELLA VULGARIS BEI JER. IN THE PRESENCE OF SELENIUM NANOAQUA CHELATES

Abstract

Aim. Study of the influence of the novel form of selenium-containing additives, selenium nanoaquachelates carboxylated with citric acid, on biomass accumulation and efficiency of the reactions of the light stage of photosynthesis in unicellular green algae Chlorella vulgaris. Materials and methods. Algae were grown under sterile conditions in 1 L flasks on liquid mineral medium at 25–26 °С. Cultures were provided with continuous irradiation with 40–42 μmol m-2·s-1 photon flux density. The solution of selenium nanoaquachelates carboxylated with citric acid was added to algal cultures immediately after inoculation. The dry mass of algae was determined gravimetrically. Modulated chlorophyll a fluorescence was measured at room temperature, and common fluorescence parameters were calculated. Results. Selenium nanoaquachelates at 0.4–4 mg/L concentrations stimulated the growth of C. vulgaris, and the increase in biomass reached 40–45%. The addition of Se nanoparticles at smaller concentrations (0.07 or 0.2 mg/L) at first caused the retardation of culture growth, but that effect disappeared after 18–24 days of cultivation. When added to C. vulgaris cultures at 0.4–4 mg/L concentrations, selenium nanoaquachelates evoked the initial increase in maximal efficiency of Photosystem II (PSII ) photochemical reactions and in the efficiency of photochemical reactions in open PSII reaction centres. After 6 days of the addition of 2 or 4 mg/L selenium nanoparticles, the fluorescence photochemical quenching coefficient also increased. As a result, the quantum yield of PSII electron transport has risen. Conclusion. Selenium nanoaquachelates carboxylated with citric acid, being added to C. vulgaris cultures at 0.4–4 mg/L concentrations, have positive effect on biomass accumulation, and transiently improve the efficiency of Photosystem II photochemical reactions as well.