Effect of light intensity on the degree of ammonia toxicity on PSII activity of Arthrospira platensis and Chlorella vulgaris.
Herein the effect of increasing light intensity on the degree of ammonia toxicity and its impact on the photosynthetic performance of Arthrospira and Chlorella was investigated using Chl fluorescence as a technique to characterize their photosystem II (PSII) activity. The results revealed that the increase of light intensity amplifies the ammonia toxicity on PSII. Chl fluorescence transients shown that at a given free ammonia (FA) concentration (100mg-N/L), the photochemistry potential decreased by increasing light intensity. The inhibition of the PSII was not reversible either by re-incubating the cells under dark or under decreased FA concentration. Moreover, the decrease of photochemical and non-photochemical quenching (NPQ) of fluorescence suggest that ammonia toxicity decreases the open available PSII centers, as well the inability of PSII to transfer the generated electrons beyond QA. The collapse of NPQ suggests that ammonia toxicity inhibits the photoprotection mechanism(s) and hence renders PSII more sensitive to photoinhibition.
Laboratory Aquatic Biology, KU Leuven Kulak, E. Sabbelaan 53, 8500 Kortrijk, Belgium; Department of Natural Resources Management and Agricultural Engineering, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece. Electronic address: markoug@aua.gr.
Giorgos
G
Markou
Laboratory Aquatic Biology, KU Leuven Kulak, E. Sabbelaan 53, 8500 Kortrijk, Belgium.
Koenraad
K
Muylaert
D000641:Ammonia / Q000633:toxicity*; D048408:Chlorella vulgaris / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D008027:Light; D055668:Photochemical Processes; D010788:Photosynthesis / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D053545:Spirulina / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects
D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D000641:Ammonia
Ammonia toxicity; Chlorophyll fluorescence; Cyanobacteria; Light intensity; Microalgae; OJIP test