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          Institute: MPI für molekulare Pflanzenphysiologie     Collection: Publikationen Pflanzenphysiologie     Display Documents

ID: 251399.0, MPI für molekulare Pflanzenphysiologie / Publikationen Pflanzenphysiologie
Investigations on the reaction pattern of photosystem II in leaves from Arabidopsis thaliana by time-resolved fluorometric analysis
Authors:Steffen, R.; Eckert, H. J.; Kelly, A. A.; Dormann, P.; Renger, G.
Date of Publication (YYYY-MM-DD):2005-03-08
Title of Journal:Biochemistry
Journal Abbrev.:Biochemistry-Us
Issue / Number:9
Start Page:3123
End Page:3133
Review Status:not specified
Audience:Not Specified
Abstract / Description:The transients of normalized fluorescence yield induced by an actinic laser flash in dark adapted leaves of Arabidopsis thaliana plants were measured with new equipment, that was developed as part of this work and permits the covarage of a wide time domain of 8 decades from 100 ns to 10 s. The raw data obtained were processed and analyzed within the framework of the "3-quencher" model with Q(A) as photochemical and P680(+.) and (3)Car as nonphotochemical quenchers. Comparative measurements with hydroxylamine treated PS II mernbrane fragments from spinach revealed that the widely used "dogma" of virtually identical efficiency of photochemical (Q(A)) and nonphotochemical (P680(+.)) quenching has to be revised: the constant of the latter exceeds that of the former by a factor of about 2. As a consequence, the probability of recombination between P680(+). and Q(A)(-) and its kinetics have to be explicitly taken into account for the interpretation of flash induced fluorescence yield transients. The analysis of the experimental data within this extended "3-quencher" model reveals that a fully consistent description is achieved for the data gathered from measurements with intact leaves from wild type plants excited with actinic laser flashes of different energies (number of photons per flash and unit area). On the basis of these results it is shown that, in dark adapted leaves excited with a single laser flash, P680(+.) is predominantly (about 80% of the total reaction) reduced by Y-Z via nanosecond kinetics and Q(A)(-) reoxidation is dominated by a kinetics of about 150 mus that are ascribed to PS II complexes with the Q(B) site occupied by PQ. The excess of excited chlorophyll singlet states decays to a significant extent via the carotenoid "triplet valve" with transient population of 3Car. The present data provide the basis for analyses of A. thaliana mutants with modified lipid content and composition. The results of these investigations are described in an accompanying report.
Free Keywords:chlorophyll-a fluorescence
; light-harvesting complex
; electron-transfer
; higher-plants
; sulfoquinovosyl diacylglycerol
; membrane-fragments
; temperature-dependence
; spinach-chloroplasts
; nanosecond reduction
; core complexes
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für molekulare Pflanzenphysiologie/Molekulare Physiologie/AG Doermann
External Affiliations:Tech Univ Berlin, Max Volmer Lab, Str 17 Juni 135, D-10623 Berlin, Germany
Tech Univ Berlin, Max Volmer Lab, D-10623 Berlin, Germany
Max Planck Inst Mol Plant Physiol, Dept Mol Physiol, D-14476 Golm, Germany
Identifiers:ISI:000227418500001 [ID No:1]
ISI:000227418500001 [ID No:2]
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