Photoacclimation in <Emphasis Type="Italic">Dunaliella tertiolecta</Emphasis> reveals a unique NPQ pattern upon exposure to irradiance |
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Authors: | Email author" target="_blank">Sven?IhnkenEmail author Jacco?C?Kromkamp John?Beardall |
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Institution: | (1) School of Biological Sciences, Monash University, Clayton, VIC, 3800, Australia;(2) Netherlands Institute of Ecology, Centre for Estuarine and Marine Ecology (NIOO-CEME), P.O. Box 140, 4400 AC Yerseke, The Netherlands |
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Abstract: | Highly time-resolved photoacclimation patterns of the chlorophyte microalga Dunaliella tertiolecta during exposure to an off–on–off (block) light pattern of saturating photon flux, and to a regime of consecutive increasing
light intensities are presented. Non-photochemical quenching (NPQ) mechanisms unexpectedly responded with an initial decrease
during dark–light transitions. NPQ values started to rise after light exposure of approximately 4 min. State-transitions,
measured as a change of PSII:PSI fluorescence emission at 77 K, did not contribute to early NPQ oscillations. Addition of
the uncoupler CCCP, however, caused a rapid increase in fluorescence and showed the significance of qE for NPQ. Partitioning
of the quantum efficiencies showed that constitutive NPQ was (a) higher than qE-driven NPQ and (b) responded to light treatment
within seconds, suggesting an active role of constitutive NPQ in variable energy dissipation, although it is thought to contribute
statically to NPQ. The PSII connectivity parameter p correlated well with F′, F
m
′ and NPQ during the early phase of the dark–light transients in sub-saturating light, suggesting a plastic energy distribution
pattern within energetically connected PSII centres. In consecutive increasing photon flux experiments, correlations were
weaker during the second light increment. Changes in connectivity can present an early photoresponse that are reflected in
fluorescence signals and NPQ and might be responsive to the short-term acclimation state, and/or to the actinic photon flux. |
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