Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5507263 | Biochimica et Biophysica Acta (BBA) - Bioenergetics | 2017 | 59 Pages |
Abstract
Fast Repetition and Relaxation chlorophyll fluorescence induction is used to estimate the effective absorption cross section of PSII (ÏPSII), to analyze phytoplankton acclimation and electron transport. The fitting coefficient Ï measures excitation transfer from closed PSII to remaining open PSII upon illumination, which could theoretically generate a progressive increase in ÏPSII for the remaining open PSII. To investigate how Ï responds to illumination we grew marine phytoplankters with diverse antenna structures (Prochlorococcus, Synechococcus, Ostreococcus and Thalassiosira pseudonana) under limiting or saturating growth light. Initial Ï varied with growth light in Synechococcus and Thalassiosira. With increasing actinic illumination PSII closed progressively and Ï decreased for all four taxa, in a pattern explicable as an exponential decay of Ï with increasing distance between remaining open PSII reaction centers. This light-dependent down-regulation of Ï allows the four phytoplankters to limit the effect of increasing light upon ÏPSII. The four structurally distinct taxa showed, however, distinct rates of response of Ï to PSII closure, likely reflecting differences in the spacing or orientation among their PSII centers. Following saturating illumination recovery of Ï in darkness coincided directly with PSII re-opening in Prochlorococcus. Even after PSII had re-opened in Synechococcus a transition to State II slowed dark recovery of Ï. In Ostreococcus sustained NPQ slowed dark recovery of Ï. In Thalassiosira dark recovery of Ï was slowed, possibly by a light-induced change in PSII spacing. These patterns of Ï versus PSII closure are thus a convenient probe of comparative PSII spacings.
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Authors
Kui Xu, Jessica L. Grant-Burt, Natalie Donaher, Douglas A. Campbell,