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FLUORESCENCE QUENCHING AND THE DIADINOXANTHIN CYCLE IN A MARINE DIATOM
Citation:
Oliazola, M., J. Roche, Z. Kolber, AND P. Falkowski. FLUORESCENCE QUENCHING AND THE DIADINOXANTHIN CYCLE IN A MARINE DIATOM. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-94/571.
Description:
The diadinoxanthin cycle (DD-cycle) in chromophyta algae involves the interconversion of two carotenoids, diadinoxanthin (DD) and diatoxanthin (DT). e investigated the kinetics of light-induced DD-cycling in the marine diatom Phaeodactylum triconutum and its role in dissipating excess excitation energy in PS IL Within 15 min following an increase in irradiance DT increased and was accompanied by a stoichiometric decrease in DD. reaction was completely blocked by dithiothreitol (DTT). econd, time-dependent, increase in DT was detected 20 min after the light shift without a concomitant decrease in DD. T accumulation from both processes was correlated with increases in non-photochemical quenching of chlorophyll fluorescence. tem-Volmer analyses suggests that changes in non-photochemical quenching resulted from changes in thermal dissipation in the PS 11 antenna and in the reaction center. he increase in non-photochemical quenching was correlated with a small decrease in the effective absorption cross section of PS 11. odel calculations suggest however that the changes in cross section are not sufficiently large to significantly reduce multiple excitation of the reaction center within the turnover time of steady-state photosynthetic electron transport at light saturation. n DTT poisoned cells, the change in non-photochemical quenching appears to result from energy dissipation in the reaction center and was associated with dec@ photochemical efficiency. I protein degradation was slightly higher in samples poisoned with DTT than in control samples. hese results suggest that while DD-cycling may dynamically alter the photosynthesis-irradiance response curve. it often limited protection against photodamage of PS II reaction centers at irradiance levels sufficient to saturate steady-state photosynthesis.