Photosynthesis of the Cyanidioschyzon merolae cells in blue, red, and white light
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ORIGINAL ARTICLE
Photosynthesis of the Cyanidioschyzon merolae cells in blue, red, and white light Eugeniusz Parys1 · Tomasz Krupnik1 · Ilona Kułak1 · Kinga Kania1 · Elżbieta Romanowska1 Received: 7 August 2020 / Accepted: 6 November 2020 / Published online: 24 November 2020 © The Author(s) 2020
Abstract Photosynthesis and respiration rates, pigment contents, C O2 compensation point, and carbonic anhydrase activity in Cyanidioschizon merolae cultivated in blue, red, and white light were measured. At the same light quality as during the growth, the photosynthesis of cells in blue light was significantly lowered, while under red light only slightly decreased as compared with white control. In white light, the quality of light during growth had no effect on the rate of photosynthesis at low O2 and high CO2 concentration, whereas their atmospheric level caused only slight decrease. Blue light reduced markedly photosynthesis rate of cells grown in white and red light, whereas the effect of red light was not so great. Only cells grown in the blue light showed increased respiration rate following the period of both the darkness and illumination. Cells grown in red light had the greatest amount of chlorophyll a, zeaxanthin, and β-carotene, while those in blue light had more phycocyanin. The dependence on O2 concentration of the C O2 compensation point and the rate of photosynthesis indicate that this alga possessed photorespiration. Differences in the rate of photosynthesis at different light qualities are discussed in relation to the content of pigments and transferred light energy together with the possible influence of related processes. Our data showed that blue and red light regulate photosynthesis in C. merolae for adjusting its metabolism to unfavorable for photosynthesis light conditions. Keywords Photosynthesis and respiration · Light quality · CO2 and O2 exchange · Chlorophyll a · Zeaxanthin and β-carotene · Red alga · Cyanidioschyzon merolae Abbreviations APC Allophycocyanin β-Car β-Carotene Γ CO2 compensation point CA Carbonic anhydrase CCM CO2-concentrating mechanism Chl a Chlorophyll a DMSO Dimethyl sulfoxide EZ Ethoxyzolamide LEDR Light-enhanced dark respiration PBSs Phycobilisomes PCB Phycocyanobilin PE Phycoerythrin PFD Photosynthetic flux density Pn Net photosynthesis * Elżbieta Romanowska [email protected] 1
Department of Molecular Plant Physiology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02‑096 Warsaw, Poland
R Dark respiration Zea Zeaxanthin
Introduction Taxonomic position, classification, and physiology of Cyanidioschyzon merolae The Cyanidioschyzon merolae is a member of Cyanidiales, and order of red algae, it is a small (1.5 × 3.5 μm in size) thermo-acidophilic unicellular alga isolated from an Italian volcanic hot springs (Merola et al. 1981). It grows best at a pH of 1.5 and a temperature of 45 °C (Albertano et al. 2000). Cyanidiales are only phototrophic organisms and eucaryotes found in acidic hot water. The cell has an extremely simple
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