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'Cation Effects' in keywords Facet   Publication Year 1975  [X]
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1Author    HansJ. RurainskiRequires cookie*
 Title    Antagonistic Relationships between Electron Transport and P700 in Chloroplasts and Intact Algae  
 Abstract    The effects of divalent salts and 3-(3,4-dichlorophenyl) -1,1-dimethylurea (DCMU) upon nicotin­ amide adenine dinucleotide phosphate (NADP) reduction and P700 in isolated chloroplasts are described and compared with the influence of DCMU on oxygen evolution and P700 in intact cells. Most experiments were carried out with a steady-state relaxation spectrometer. A kinetic mechanism for the estimation of P700 fluxes is proposed and experimentally tested. Good agreement between theory and experiment was found. Concurrent measurements of P700 and NADP reduction revealed two antagonisms: addition of divalent cations caused an increase in the yield of NADP reduction and a decrease in the yield of P700 . Conversely, in the presence of Mg2+ low concentrations of DCMU decreased the yield of NADP reduction and increased the yield of P700 . Aging of the chloroplasts at 30 °C exerted a similar effect. With far-red actinic light, Mg2* stimulated the yield of NADP reduction without affecting the flux. Also, in the absence of Mg2+ , DCMU inhibited both reactions although P700 required a higher herbicide concentration for fractional inhibition than NADP reduction. In the presence of Mg2*, chloroplasts resembled intact algae in which a high rate of oxygen evolution was accompanied by little P700 turn-over. Titration with DCMU decreased the rate of photosynthesis and increased P700 flux. On the whole, the data suggest that P700 relaxing in 20 msec is not directly involved in linear electron transport. 
  Reference    (Z. Naturforsch. 30c, 761 [1975]; received July 23 1975) 
  Published    1975 
  Keywords    Relaxation Spectroscopy, Photosynthesis, NADP Reduction, Cation Effects 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0761.pdf 
 Identifier    ZNC-1975-30c-0761 
 Volume    30