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1979 (1)
1978 (2)
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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 
2Author    Salil Bose, GeorgeE. HochRequires cookie*
 Title    Mg2+-H + Exchange in Chloroplast Membranes in Dark  
 Abstract    Protons are released from unillum inated chloroplasts after the addition of Mg2+. The greatest num ber of protons was measured at pH 6.5 and corresponded to 0.6 mol protons per mol chloro­ phyll. 
  Reference    Z. Naturforsch. 33c, 105 (1978); received January 2 1978 
  Published    1978 
  Keywords    Chloroplast M embranes, Cation Effects, Proton Exchange 
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 TEI-XML for    default:Reihe_C/33/ZNC-1978-33c-0105.pdf 
 Identifier    ZNC-1978-33c-0105 
 Volume    33 
3Author    Govindjee, Paul Mathis, Claudie Vem Otte, Daniel Wong, Satham Saphon, ThomasW. Ydrzynskic, Jean-M Arie BriantaisRequires cookie*
 Title    Cation Effects on System II Reactions in Thylakoids: Measurements on Oxygen Evolution, the Electrochromic Change at 515 Nanometers, the Primary Acceptor and the Primary Donor  
 Abstract    Divalent cations are known to decrease the "spillover" of excitation energy from photosystem II (PS II) to PS I. At low light intensities, this does lead to an increased quantum yield of photo­ reactions in PS II. Contrary to some suggestions that PS II is activated at high light intensities, or in strong flashes of light by the addition of Mg2+, we suggest here that Mg2+ ions may not activate reaction center II, P 680. After brief light flashes, we do not find any significant enhancement in (a) 0 2 yield/flash, (b) proton yield/flash, (c) the amplitude of charge separation in PS II, as moni­ tored by 515 nm absorbance change, and (d) the amplitude of the reduced primary acceptor, as monitored by 320 nm absorbance change. Data on absorbance change at 820 nm suggest that the absence of Mg2+ does not lead to inactivation of electron donation to P 680+. 
  Reference    Z. Naturforsch. 34c, 826—830 (1979); received July 9 1979 
  Published    1979 
  Keywords    Photosynthesis, Flash Yields, Cation Effects, Photosystem II, Thylakoids 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0826.pdf 
 Identifier    ZNC-1979-34c-0826 
 Volume    34 
4Author    HansJ. Rurainski, Gerhard MaderRequires cookie*
 Title    The Effect of M g 2+ on the Reduction of N A D P by an Artificial Electron D onor  
 Abstract    The effect of M g 2+ on the light-dependent reduction of N A D P by an artificial electron donor has been investigated with isolated broken chloroplasts. In both short and long wavelength actinic light, addition of the salt under most conditions stimulates the yield and the saturation rate. The magnitude of the stimulation is a function of pH. T he data indicate that previous interpreta­ tions of the M g 2+ effect in this system invoking changes in the spill-over rate between the photo­ systems is no longer tenable. It is suggested that addition of the salt causes activation of inactive reaction centers. 
  Reference    Z. Naturforsch. 33c, 664 (1978); received August 7 1978 
  Published    1978 
  Keywords    Photosynthesis, Photosystem I, Cation Effect, N A D P Reduction 
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 TEI-XML for    default:Reihe_C/33/ZNC-1978-33c-0664.pdf 
 Identifier    ZNC-1978-33c-0664 
 Volume    33