title: Photon- and carbon-use efficiency in Ulva rigida at different CO2 and N levels.
abstract: The seaweed Ulva rigida C. Agardh (Chlorophyta) was cultured under two CO(2) conditions supplied through the air bubbling system: non-manipulated air and 1% CO(2)-enriched aeration. These were also combined with N sufficiency and N limitation, using nitrate as the only N source. High CO(2) in U. rigida led to higher growth rates without increasing the C fixed through photosynthesis under N sufficiency. Quantum yields for charge separation at photosystem II (PSII) reaction centres (phi(PSII)) and for oxygen evolution (phi(O2)) decreased at high CO(2) even in N-sufficient thalli. Cyclic electron flow around PSII as part of a photoprotection strategy accompanied by decreased antennae size was suspected. The new re-arrangement of the photosynthetic energy at high CO(2) included reduced investment in processes other than C fixation, as well as in carbon diverted to respiration. As a result, quantum yield for new biomass-C production (phi(growth)) increased. The calculation of the individual quantum yields for the different processes involved allowed the completion of the energy flow scheme through the cell from incident light to biomass production for each of the CO(2) and N-supply conditions studied.
authors.affiliation: Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain. gordillo@uma.es
authors.forename: Francisco J L
authors.initials: FJ
authors.lastname: Gordillo
authors.forename: Félix L
authors.initials: FL
authors.lastname: Figueroa
authors.forename: F Xavier
authors.initials: FX
authors.lastname: Niell
mesh_terms: D002245:Carbon Dioxide / Q000494:pharmacology*; D019069:Cell Respiration / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008027:Light; D008954:Models, Biological; D009584:Nitrogen / Q000494:pharmacology*; D010788:Photosynthesis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D044445:Ulva / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D002734:Chlorophyll; D002245:Carbon Dioxide; D009584:Nitrogen