The effects of excess irradiance on photosynthesis in the marine diatom Phaeodactylum tricornutum

The response of Phaeodactylum tricornutum to excess light was remarkably similar to that observed in higher plants and green algae and was characterized by complex changes in minimal fluorescence yields of fully dark-adapted samples and declines in maximum variable fluorescence levels and oxygen evo...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1994-10, Vol.106 (2), p.763-770
Main Authors: Claire S. Ting, Owens, Thomas G.
Format: Article
Language:English
Subjects:
bacillariophyceae
chlorophylle
Chlorophylls
clorofilas
Diatoms
echange gazeux
Environmental and Stress Physiology
Fluorescence
fluorescencia
fotoinhibicion
fotosistemas
gas exchange
Insect antennae
intercambio de gases
Kinetics
light
lumiere
luz
oxigeno
oxygen
oxygene
Photochemistry
Photoinhibition
Photons
Photosynthesis
photosysteme
photosystems
Plants
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Summary:The response of Phaeodactylum tricornutum to excess light was remarkably similar to that observed in higher plants and green algae and was characterized by complex changes in minimal fluorescence yields of fully dark-adapted samples and declines in maximum variable fluorescence levels and oxygen evolution rates. In our study the parallel decreases in the effective rate constant for photosystem II (PSII) photochemistry the variable fluorescence yield of a dark-adapted sample and light-limited O2 evolution rates after short (0-10 min) exposures to photoinhibitory conditions could not be attributed to damage or down-regulation of PSII reaction centers. Instead, these changes were consistent with the presence of nonphotochemical quenching of PSII excitation energy in the antennae. This quenching was analogous to that component of nonphotochemical quenching studied in higher plants that is associated with photoinhibition of photosynthesis and/or processes protecting against photoinhibition in that it did not relax readily in the dark and persisted in the absence of a bulk transthylakoid proton gradient. The quenching was most likely associated with photoprotective processes in tne PSII antenna that reduced the extent of photoinhibitory damage particularly after longer exposures. Our results suggest that a large population of damaged slowly recovering PSII centers did not form in Phaeodactylum even after 60 min of exposure to excess actinic light.
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.106.2.763