title: Photosynthetic quantum yield dynamics: from photosystems to leaves.
abstract: The mechanisms underlying the wavelength dependence of the quantum yield for CO(2) fixation (α) and its acclimation to the growth-light spectrum are quantitatively addressed, combining in vivo physiological and in vitro molecular methods. Cucumber (Cucumis sativus) was grown under an artificial sunlight spectrum, shade light spectrum, and blue light, and the quantum yield for photosystem I (PSI) and photosystem II (PSII) electron transport and α were simultaneously measured in vivo at 20 different wavelengths. The wavelength dependence of the photosystem excitation balance was calculated from both these in vivo data and in vitro from the photosystem composition and spectroscopic properties. Measuring wavelengths overexciting PSI produced a higher α for leaves grown under the shade light spectrum (i.e., PSI light), whereas wavelengths overexciting PSII produced a higher α for the sun and blue leaves. The shade spectrum produced the lowest PSI:PSII ratio. The photosystem excitation balance calculated from both in vivo and in vitro data was substantially similar and was shown to determine α at those wavelengths where absorption by carotenoids and nonphotosynthetic pigments is insignificant (i.e., >580 nm). We show quantitatively that leaves acclimate their photosystem composition to their growth light spectrum and how this changes the wavelength dependence of the photosystem excitation balance and quantum yield for CO(2) fixation. This also proves that combining different wavelengths can enhance quantum yields substantially.
authors.affiliation: Department of Plant Sciences, Wageningen University, Wageningen, The Netherlands. sander.hogewoning@gmail.com
authors.forename: Sander W
authors.initials: SW
authors.lastname: Hogewoning
authors.forename: Emilie
authors.initials: E
authors.lastname: Wientjes
authors.forename: Peter
authors.initials: P
authors.lastname: Douwstra
authors.forename: Govert
authors.initials: G
authors.lastname: Trouwborst
authors.forename: Wim
authors.initials: W
authors.lastname: van Ieperen
authors.forename: Roberta
authors.initials: R
authors.lastname: Croce
authors.forename: Jeremy
authors.initials: J
authors.lastname: Harbinson
mesh_terms: D002338:Carotenoids / Q000378:metabolism; D018553:Cucumis sativus / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002338:Carotenoids