Wavelength dependence of the fluorescence emission under conditions of open and closed Photosystem II reaction centres in the green alga Chlorella sorokiniana |
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Authors: | Federico Rizzo Giuseppe ZucchelliRobert Jennings Stefano Santabarbara |
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Institution: | Istituto di Biofisica, Consiglio Nazionale delle Ricerche, via Celoria 26, 20133 Milano, Italy; Dipartimento di Bioscienze, Università di Milano, via Celoria 26, 20133 Milano, Italy |
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Abstract: | The fluorescence emission characteristics of the photosynthetic apparatus under conditions of open (F0) and closed (FM) Photosystem II reaction centres have been investigated under steady state conditions and by monitoring the decay lifetimes of the excited state, in vivo, in the green alga Chlorella sorokiniana. The results indicate a marked wavelength dependence of the ratio of the variable fluorescence, FV = FM − F0, over FM, a parameter that is often employed to estimate the maximal quantum efficiency of Photosystem II. The maximal value of the FV/FM ratio is observed between 660 and 680 nm and the minimal in the 690–730 nm region. It is possible to attribute the spectral variation of FV/FM principally to the contribution of Photosystem I fluorescence emission at room temperature. Moreover, the analysis of the excited state lifetime at F0 and FM indicates only a small wavelength dependence of Photosystem II trapping efficiency in vivo. |
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Keywords: | PSI(II) Photosystem I (II) LHC Light Harvesting Complex Chl chlorophyll DAS Decay Associated Spectra F0 fluorescence level at open PSII reaction centres FM fluorescence level at closed PSII reaction centres FV variable fluorescence ΦPSIImax maximal photochemical yield of PSII τ(av) (average) lifetime CP chlorophyll protein complex |
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