title: Wavelength dependence of the fluorescence emission under conditions of open and closed Photosystem II reaction centres in the green alga Chlorella sorokiniana.
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 680nm and the minimal in the 690-730nm 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.
authors.affiliation: 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.
authors.forename: Federico
authors.initials: F
authors.lastname: Rizzo
authors.affiliation: 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.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zucchelli
authors.affiliation: 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.
authors.forename: Robert
authors.initials: R
authors.lastname: Jennings
authors.affiliation: 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. Electronic address: stefano.santabarbara@cnr.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Santabarbara
mesh_terms: D002708:Chlorella / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D045332:Photosystem II Protein Complex
keywords: Excited state dynamics; Maximal photochemical efficiency; Photochemical yield; Photosystem II; Variable fluorescence