Influence of spectral range and carbon and nitrogen sources on oxygen evolution and Emerson enhancement in Chlamydomonas reinhardtii

Abstract

Chlamydomonas reinhardtii was grown in medium with different carbon (acetate, CO2, or both), and nitrogen (ammonium chloride, peptone, urea) sources and under light of different spectral composition. The light-dark cycles were found more suitable for mixotrophic growth than continuous irradiation. Both blue (BR) and red (RR) radiations decreased photosynthetic capacity of mixotrophic cells compared to "white light" (WL). Effect of RR was associated with photon distribution favouring photosystem 1 (PS1) suggesting increased cyclic phosphorylation. Mixotrophic growth in 10 mM NH4Cl increased photosynthetic oxygen evolution compared to standard concentration of 5 mM NH4Cl used for growing C. reinhardtii. Autotrophic growth stimulated the photosynthetic capacity compared to mixotrophic one. However, higher photosynthetic capacity was achieved for mixotrophic cells by growing them at high NH4+/K+ ratio and high phosphate concentration.