title: A novel P700 redox kinetics probe for rapid, non-intrusive and whole-tissue determination of photosystem II functionality, and the stoichiometry of the two photosystems in vivo.
abstract: We sought a rapid, non-intrusive, whole-tissue measure of the functional photosystem II (PS II) content in leaves. Summation of electrons, delivered by a single-turnover flash to P700(+) (oxidized PS I primary donor) in continuous background far-red light, gave a parameter S in absorbance units after taking into account an experimentally determined basal electron flux that affects P700 redox kinetics. S was linearly correlated with the functional PS II content measured by the O(2) yield per single-turnover repetitive flash in Arabidopsis thaliana expressing an antisense construct to the PsbO (manganese-stabilizing protein in PS II) proteins of PS II (PsbO mutants). The ratio of S to z(max) (total PS I content in absorbance units) was comparable to the PS II/PS I reaction-center ratio in wild-type A. thaliana and in control Spinacea oleracea. Both S and S/z(max) decreased in photoinhibited spinach leaf discs. The whole-tissue functional PS II content and the PS II/photosystem I (PS I) ratio can be non-intrusively monitored by S and S/z(max), respectively, using a quick P700 absorbance protocol compatible with modern P700 instruments.
authors.affiliation: Division of Plant Science, Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra, Australia.
authors.forename: Husen
authors.initials: H
authors.lastname: Jia
authors.forename: Simon A
authors.initials: SA
authors.lastname: Dwyer
authors.forename: Da-Yong
authors.initials: DY
authors.lastname: Fan
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Han
authors.forename: Murray R
authors.initials: MR
authors.lastname: Badger
authors.forename: Susanne
authors.initials: S
authors.lastname: von Caemmerer
authors.forename: Wah Soon
authors.initials: WS
authors.lastname: Chow
mesh_terms: D017360:Arabidopsis / Q000378:metabolism* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism*; D004579:Electron Transport; D007700:Kinetics; D008954:Models, Biological; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D018724:Spinacia oleracea / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; C001785:chlorophyll P 700; D010100:Oxygen