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Light-Harvesting Function in the Diatom Phaeodactylum tricornutum: II. Distribution of Excitation Energy between the Photosystems.
MedLine Citation:
PMID:  16664695     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
The distribution of excitation energy between photosystems I and II (PSI and PSII) was investigated in the marine diatom Phaeodactylum tricornutum (Bohlin) using light-induced changes in fluorescence yield and rate of modulated O(2) evolution. The intensity dependence of the fast fluorescence rise in dark adapted cells (+/-DCMU) suggests that light absorbed by the major antenna complex was not delivered preferentially to PSII but is more equally distributed between the photosystems. Reversible, slow fluorescence yield changes measured in the absence of DCMU were correlated with decreased initial fluorescence and rate constants for PSII photochemistry, increased variable fluorescence, alteration of the fluorescence excitation and emission spectra, and could be effected by either 510 nm (PSII) or 704 nm (PSI) light. Slow, reversible fluorescence yield changes were also observed in the presence of DCMU, but were characterized by a loss of both initial and variable fluorescence and could not be induced by PSI light. The absence of slow changes in the yield of fluorescence and rate of modulated O(2) evolution, following addition or removal of PSI background light to modulated PSII excitation, does not support regulation of excitation energy density in PSI at the expense of PSII. The results suggest that adjustments are made at the level of excitation energy transfer to the PSII reaction center which prevent prolonged loss of photosynthetic capacity. Energy distribution is regulated by ionic distributions independently of the plastoquinone pool redox state. These differences in light-harvesting function are probably a response to the aquatic light field and may account for the success of diatoms in low and variable light environments.
Authors:
T G Owens
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Plant physiology     Volume:  80     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  1986 Mar 
Date Detail:
Created Date:  2010-06-29     Completed Date:  2010-07-08     Revised Date:  2010-09-15    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  739-46     Citation Subset:  -    
Affiliation:
Section of Plant Biology, Cornell University, Ithaca, New York 14853.
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