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1984 (1)
1983 (1)
1979 (1)
1Author    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 
2Author    GeorgH. Schmid, Pierre ThibaultRequires cookie*
 Title    Studies on the S-State Distribution in Euglena gracilis  
 Abstract    When Euglena gracilis is dark adapted for 10 min or more, oxygen evolution as the conse­ quence of short (5 usee) saturating light flashes does not show the picture of a damped oscillation with a periodicity o f 4, as known from the literature. The overall picture of this flash pattern is given by the fact that 0 2-evolution in the First two flashes is practically zero and rises from there onward in a continuous manner to the steady state with barely any visible oscillation at all. However, a second flash sequence fired one to two minutes after this first sequence induces an oxygen evolution pattern which is barely distinguishable from the well known usual Chlorella vulgaris pattern. The phenomenon is not influenced by changes in the oxygen tension nor do additions of chemicals like CCCP, sodium azide, or reducing agents like hydroxylamine or hydrogen peroxide substantially alter the described behavior. Deactivation experiments give the overall impression that the deactivation of the S-states is slower than with Chlorella. Hydroxylamine strongly accelerates the deactivation. The analysis of the S-state distribution in a four and five state Kok-model suggests that dark adapted Euglena is in a more reduced condition than dark adapted Chlorella. It looks as if dark adapted Euglena were in a condition which would correspond to 60 percent S_|, 30 percent S0 and 10 percent S). The experimental flash sequence of such dark adapted cells fits best a synthetic sequence when the misses are in the region of 2 0 -2 5 percent, with double hitting playing practically no role at all (the first two flashes are zero!). The impression that dark adapted Euglena starts its oxygen evolution from a more reduced state is strengthened by the analysis of room temperature fluorescence induction (Kautsky effect). It can be shown that the fluorescence induction curve o f Euglena corresponds to that of Chlorella cells provided the latter have been briefly treated with a strong reductant such as sodium dithionite. 
  Reference    Z. Naturforsch. 38c, 60—6 (1983); received September 1982 
  Published    1983 
  Keywords    Flash Yield, Oxygen, Euglena, Fluorescence Induction 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0060.pdf 
 Identifier    ZNC-1983-38c-0060 
 Volume    38 
3Author    Fabrice Franck, GeorgH. SchmidRequires cookie*
 Title    Flash Pattern of Oxygen Evolution in Greening Etioplasts of Oat  
 Abstract    Etioplasts isolated from oat leaves that have received two 5 m in illum ination periods, spaced apart by a 90 min dark interval, are able to evolve oxygen. If this oxygen evolution is measured as consequence o f short saturating light flashes a pattern is obtained w hich in agreem ent with the Kok-Joliot model shows a dam ped oscillation w ith a periodicity o f four. As usual for most other systems the maximum flash yield is observed under the third flash. In continuous light such slightly greened etioplasts show a small oxygen gush. From our studies it appears that the second 5 min illumination period is obligatory for oxygen evolution. O m ission o f this period leads to a condition in which under flashes strictly no oxygen is evolved. In continuous light under these conditions no oxygen gush but rather an uptake is observed after onset o f illum ination. It appears that in greening etioplasts the flash pattern shows som e peculiarities when compared to the normal green conditions. Thus, a flash sequence o f a greening etioplast always shows a substantial positive amperometric signal under the first flash. The h alf tim e o f the state which would belong to this signal is 3 to 4 min in a greening etioplast, isolated from leaves that have received 2 h light. In the course o f greening this h alf tim e decreases continuously and reaches a normal and constant value o f approx. 1 0 s in chloroplasts from green oat or etiochloroplasts that are prepared from leaves that have received 15 h o f light. The result is discussed in terms o f metastable S3 which seems to be a property o f the developing oxygen evolving system in greening oat leaves. In the greening system as we use it is shown for the first tim e that the photoenzym e protochlorophyllide chlorophyllide reductase is D C M U sensitive. 
  Reference    Z. Naturforsch. 39c, 1091 (1984); received August 17 1984 
  Published    1984 
  Keywords    Flash Yield, Oxygen, S-States, Etioplasts 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-1091.pdf 
 Identifier    ZNC-1984-39c-1091 
 Volume    39