Photosynthetica · 1999 · 18 citations · 37 references
Life SciencesPlant BiologyPlant SciencesPhotosynthesisPlant BiochemistryPlant PhysiologyLight HarvestingPhotosynthesis BiochemistryPhotosynthetic Energy ConversionPhotosynthetic Energy TransferPhotosynthetic PigmentsRed AlgaeFluorescence QuenchingIrradiation EffectsPh Dependence Of FluorescencePhotoprotection MechanismsPhotoprotective MechanismsPhotosynthetic ControlProton Gradient FormationThylakoid Proton Gradient
Plants have developed various photoprotective mechanisms to resist irradiation stress. One of the photoprotective mechanisms described in the literature for LHC2-containing organisms involves a down-regulation of photosystem (PS) 2 occurring simultaneously with the build-up of a proton gradient across the thylakoid membrane (ΔpH). It is often correlated with deepoxidation of xanthophylls located in LHC2. In Rhodophyta instead of LHC2, the peripheral antenna of PS2 consists of a large extramembrane complex, the phycobilisome (PBS), which transfers its excitation to the core antennae of PS2 composed of the CP43 and CP47 protein-chlorophyll complexes and there is no xanthophyll cycle. In the red alga Rhodella violacea a ΔpH-dependent chlorophyll (Chl) a fluorescence quenching can be formed. We characterised this quenching, studied the effects of various irradiances and inhibitors. Under photoinhibitory conditions, the ΔpH-dependent Chl fluorescence quenching exerts a photoprotective role and delays the kinetics of photoinhibition. It is the first time that such a photoprotective mechanism is described in PBS-containing organisms.
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