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1Author    J.J S Van Rensen, D. Wong, GovindjeeRequires cookie*
 Title    Characterization of the Inhibition of Photosynthetic Electron Transport in Pea Chloroplasts by the Herbicide 4,6-Dinitro- o-cresol by Comparative Studies with 3-(3,4-Dichlorophenyl)-l,l- dimethylurea  
 Abstract    An attempt to characterize the mechanism of inhibition of photosynthetic electron transport in isolated pea chloroplasts by the herbicide 4,6-dinitro-o-cresol (DNOC) by a comparison with the effects of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) revealed the following: 
  Reference    Z. Naturforsch. 33c, 413 (1978); received April 12 1978 
  Published    1978 
  Keywords    Photosynthesis, Electron Transport, Fluorescence, Herbicides 
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 TEI-XML for    default:Reihe_C/33/ZNC-1978-33c-0413.pdf 
 Identifier    ZNC-1978-33c-0413 
 Volume    33 
2Author    Magdolna Droppa, Sándor Demeter, Zsuzsa Rózsa, G. Ábor HorváthRequires cookie*
 Title    Reinvestigation of the Effects of Disalicylidenepropanediamine (DSPD) and 2-HeptyM-hydroxyquinoline-N-oxide (HQNO) on Photosynthetic Electron Transport  
 Abstract    The effects of disalicylidenepropanediamine (DSPD) and 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO) on photosynthetic electron transport have been reexamined. The results confirm earlier observations that lower concentrations of DSPD (< 100 hm) block electron transport at the levels of ferredoxin and plastocyanin. High concentrations o f DSPD even inhibit electron transport from HaO -> pBQ, suggesting that DSPD has an inhibitory site in PS II as well. Thermoluminescence curves o f DSPD and DCMU treated chloroplasts were very similar, showing that the third inhibitory site o f DSPD is similar to that o f DCMU. Both oxidized and reduced HQNO, (0 .6 -6 hm) blocked electron transport from H20 -* pBQ, H20 -*■ MV/FeCy to a similar extent. The effect of HQNO on thermoluminescence showed that its inhibitory site is probably located before that o f DCMU. At higher concentration (> 6 h m) , the H20 -*■ MV/FeCy reactions were more strongly inhibited by oxidized HQNO than those occuring from H20 -> pBQ, suggesting that a new site o f inhibition must also be considered. The dark decay of the P 700 signal was not influenced by the addition o f oxidized HQNO which shows that the new inhibitory site of HQNO is located between plastoquinone and P 700. The reduced form of HQNO did not inhibit non-cyclic electron transport around PS I. Indeed, at higher concentrations, reduced HQNO even accelerates electron flow from DCIP -» MV and the dark reduction of P 700, thus suggesting that this compound has a "donor-mediator" function in PS I. 
  Reference    Z. Naturforsch. 36c, 109 (1981); received September 8/October 28 1980 
  Published    1981 
  Keywords    Inhibitors, Electron Transport, Chloroplasts, Thermoluminescence 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-0109.pdf 
 Identifier    ZNC-1981-36c-0109 
 Volume    36 
3Author    G. Ünter, D. Ö. RinRequires cookie*
 Title    The Effect of Deoxycholate-Treatment to the Photoreactions of the Active Pigments in Photosynthesis  
 Abstract    In the heavy fraction of deoxycholate-treated spinach chloroplasts the chlorophyll an activity is high and the chlorophyll a\ activity is low when no artificial electron donor is added. The addition of the photosystem I donor system N-methyl-phenazonium sulphate plus sodium ascorbate (PMS + Asc) leads to a complete reactivation of the chlorophyll ai reaction. The addition of the photo­ system II donor system p-benzohydroquinone plus sodium ascorbate (HQ + Asc) leads to an inhibi­ tion of the chlorophyll an activity. From these results we conclude: 1. Besides an interruption of the linear electron flow between the two photosystems deoxycholate-treatment leads to a block of the electron flow from water to photosystem II. 2. In deoxycholate-treated chloroplasts the linear electron flow in photosystem II just like in Tris­ washed, heat-treated or aged chloroplasts, is replaced by a cyclic one. 
  Reference    (Z. Naturforsch. 31c, 64 [1976]; received August 19 1975) 
  Published    1976 
  Keywords    Photosynthesis, Deoxycholate-Treatment, Electron Transport, Flash Excitation 
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 TEI-XML for    default:Reihe_C/31/ZNC-1976-31c-0064.pdf 
 Identifier    ZNC-1976-31c-0064 
 Volume    31 
4Author    Klaus Pfister, CharlesJ. ArntzenRequires cookie*
 Title    The Mode of Action of Photosystem II-Specific Inhibitors in Herbicide-Resistant Weed Biotypes  
 Abstract    This report reviews studies which provide evidence defining the mode of action and site of action of photosystem II (PS II) herbicides; the involvement of the secondary electron carrier on the reducing side of PS II (called B) is indicated as the target site for these compounds. These studies of the action of PS II-inhibitors were perform ed in chloroplasts of various weed species in order to define the mechanism which is responsible for herbicide tolerance at the level of chloroplast mem branes in newly discovered triazine-resistant weed biotypes. M any species of triazine-resistant weed biotypes have been collected in N orth America and Europe. W here data is available, these plants have been found to share the following common fe atu res: a) they were discovered in areas where triazine herbicides had been used repeatedly, b) resistance to the triazines is extrem e; it is not due to a m inor shift in herbicidal response, c) no changes in herbicide uptake, translocation or metabolism — as compared to susceptible bio­ types — can be detected, d) resistance is selective for only certain classes of photosynthetic herbicides, and, e) chloroplasts isolated from triazine-resistant weeds display high preferential resistance to the triazines in assays of photosystem II partial reactions. To focus on the mechanism which regulates preferential herbicide activity, we have characterized susceptible and resistant chloroplasts in the presence and absence of herbicides. Properties of the PS II complex of chloroplasts from several different triazine-resistant weed biotypes share the fol­ lowing tr a its : a) the herbicide binding site (as measured by direct binding of radiolabeled herbicides or by in­ hibition experiments) is modified such that the affinity for triazines is dram atically reduced. b) alterations in response to many PS II-herbicides occur such th at the triazine-resistant chloro­ plasts are very strongly resistant to all sym m etrical triazines, strongly resistant to assymmetrical triazinones, partially resistant to pyridazones and uracils, only slightly resistant to ureas or amides, and increasingly susceptible to nitrophenols, phenols and the herbicide bentazon (all as compared to susceptible chloroplasts), c) there is a change in the reaction kinetics of the electron transport step between the prim ary and secondary electron acceptors (referred to as Q and B), and d) in two examples, specific small changes in a m em brane polypeptide can be detected in the resistant thylakoids. We suggest that certain amino acids or segments of the apoprotein of B (the bound quinone which acts as the secondary electron carrier) are modified or deleted in these chloroplasts. Such a polypeptide change could affect both the redox poising of the Q~/B reaction pair, and the specific binding of herbicides. 
  Reference    Z. Naturforsch. 34c, 996—1009 (1979); received June 29 1979 
  Published    1979 
  Keywords    Herbicide, Resistance, Photosynthesis, Electron Transport, Inhibitors 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0996.pdf 
 Identifier    ZNC-1979-34c-0996 
 Volume    34 
5Author    J.J S Van Rensen, J. H. HobéRequires cookie*
 Title    Mechanism of Action of the Herbicide 4,6-Dinitro-o-cresol in Photosynthesis  
 Abstract    The herbicide 4,6-dinitro-o-cresol inhibits electron transport to ferricyanide and non-cyclic photophosphorylation for 50% at about 15 /am. At higher concentrations the photosystem I depen­ dent M ehler reaction ascorbate/dichlorophenolindophenol to m ethyl viologen is stim ulated, while cyclic photophosphorylation is inhibited. The herbicide thus is an inhibitory uncoupler. A lthough the chemical structure of 4,6-dinitro-o-cresol is different from th a t of the diuron-type herbicides, its site and mechanism of action is similar. Both 4,6-dinitro-o-cresol and diuron inhibit electron transport between the prim ary electron acceptor of Photosystem II and the plastoquinone pool. This causes a closing of the reaction centers of Photosystem II. The interaction with the inhibited molecule however is different for the two herbicides. 
  Reference    Z. Naturforsch. 34c, 1021 (1979); received May 26 1979 
  Published    1979 
  Keywords    Photosynthesis, Electron Transport, Photophosphorylation, H erbicides 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-1021.pdf 
 Identifier    ZNC-1979-34c-1021 
 Volume    34 
6Author    Marc Symons, Anthony CroftsRequires cookie*
 Title    Flash-Induced Electrochromic Band Shifts, is It a Simple Mechanism?  
 Abstract    The flash-induced carotenoid bandshifts have been studied for various strains of both Rho-dopseudomonas sphaeroides and capsulata. A technique for calculating shifts o f isobestic points down to 0.05 nm is described. To this end, special attention has been paid to the appropriate cor­ rection for reaction center absorbance changes occuring concommitantly with the carotenoid bandshifts. Plots of the wavelength o f the isobestic point versus the corresponding absorption changes at the maximum o f the difference spectrum have been made, suggesting the existence o f different pools of carotenoids. The various pools of carotenoids seem to have different sizes, in­ ducing non-linearities in the plots. In some cases spectral differences of the pools have to be assumed. A possible interpretation o f the results would be that each electrogenic span of the electron transport chain is to be associated with its own pool of carotenoids, all the pools behaving in somewhat independant way. We discuss possible difficulties in making those measurements. 
  Reference    Z. Naturforsch. 35c, 139—144 (1980); received August 16 1979 
  Published    1980 
  Keywords    Electrochromism, Carotenoids, Electron Transport, Membrane Potential, Photosynthesis 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0139.pdf 
 Identifier    ZNC-1980-35c-0139 
 Volume    35 
7Author    Klaus Pfister, H. Artm, K. Lichtenthaler, G. Ünther Burger, Hans Musso, M.Anuel ZahnRequires cookie*
 Title    The Inhibition of Photosynthetic Light Reactions by Halogenated Naphthoquinones  
 Abstract    Halogenated naphthoquinones act as inhibitors o f photosynthetic electron flow. I50 concentra­ tion for inhibition of methylviologen reduction were found to range between 2 x 10-5 m to 2 x 10-6 M. Comparing their effects on several partial reactions o f electron flow, the inhibition site o f the naphthoquinones was found to be at the reducing site o f PS II. Studies o f fluorescence transients in presence o f halogenated naphthoquinones give further evidence for a site action similar to that o f diuron and different to that of DBMIB. All naphthoquinones act as quenchers o f chlorophyll fluorescence with pure chlorophyll a, and with much higher efficiency in green algae and chloroplasts. It is concluded, that the halogenated naphthoquinones act similar to PS II-inhibitors like diuron, but do not share a common binding site at the PS II-complex. Implications of a possible involvement of phylloquinone K 1 in photosynthetic electron transport are discussed. The synthesis o f 2-chloro-as well as 2-bromo-3-isopropyl-1,4-naphthoquinone is described. 
  Reference    Z. Naturforsch. 36c, 645—655 (1981); received April 271981 
  Published    1981 
  Keywords    Chlorophyll Fluorescence, Electron Transport, Inhibitors, Naphthoquinones, Photosynthesis, Quenchers 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-0645.pdf 
 Identifier    ZNC-1981-36c-0645 
 Volume    36 
8Author    G. Erard Van Den Berg, M. Arjo, B. Randse, Jaco, T. Ip, D. U. Ph, A.R B VRequires cookie*
 Title    Effects of Substituted 2-Phenylamino-l,4,5,6-tetrahydropyrimidines on ATP Formation in Isolated Spinach Chloroplasts  
 Abstract    The effects o f a series o f 2-arylam ino-l,4,5,6-tetrahydropyrim idines on photosynthesis in spin­ ach chloroplast were studied. The com pounds proved to be uncouplers o f photophosphorylation, while inhibition o f electron transport occurred at higher concentrations. These effects were rather irreversible and the activity increased with lipophilicity. Inhibition o f electron transport could not be reversed by trypsin treatmeni. Loss o f membrane integrity m ight be the underlying m echanism o f these effects. 
  Reference    Z. Naturforsch. 37c, 651—657 (1982); received April 2 1982 
  Published    1982 
  Keywords    Arylaminopyrimidines, Photophosphorylation, Electron Transport, Chloroplasts, uncouplers 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0651.pdf 
 Identifier    ZNC-1982-37c-0651 
 Volume    37 
9Author    J.J S Van RensenRequires cookie*
 Title    Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow  
 Abstract    The reactivation o f the Hill reaction in C 0 2-depleted broken chloroplasts by various concen­ trations o f bicarbonate was measured in the absence and in the presence o f photosystem II herbicides. It appears that these herbicides decrease the apparent affinity o f the thylakoid membrane for bicarbonate. Different characteristics o f bicarbonate binding were observed in chloroplasts o f triazine-resistant Amaranthus hybridus com pared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Q B-protein and their interference with photosynthetic electron transport. 
  Reference    Z. Naturforsch. 39c, 374—377 (1984); received N ovem ber 15 1983 
  Published    1984 
  Keywords    Photosynthesis, Electron Transport, H erbicides, Bicarbonate, Formate 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0374.pdf 
 Identifier    ZNC-1984-39c-0374 
 Volume    39 
10Author    G. Á Bor Horváth, M. Agdolna, D. Roppa, Ágnes PuskáRequires cookie*
 Title    Fluorescence Induction Characteristics of Wild-Type and Herbicide-Resistant Strain of the Photosynthetic Bacterium Rhodobacter capsulatus  
 Abstract    Fluorescence induction characteristics have been studied in wild-type and atrazine-resistant mutant o f Rhodobacter capsulatus. Fluorescence induction was found to be a useful technique to monitor the altered electron transfer in the atrazine-resistant mutants as well as in the differ­ ent membrane fractions o f wild-type R. capsulatus. In both cases, the proportion o f the fast rise o f variable fluorescence was increased indicating the enhancement o f QA. In the mutant strain, the / 50 value o f triazine herbicide terbutryn was increased by 1 0 0 -fold whereas the natu­ ral resistance o f R . capsulatus against diuron was abolished by the mutation. 
  Reference    Z. Naturforsch. 45c, 452 (1990); received N ovem ber 9 1989 
  Published    1990 
  Keywords    Fluorescence Induction, Electron Transport, Herbicide, Purple Bacteria, Photosynthesis 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0452.pdf 
 Identifier    ZNC-1990-45c-0452 
 Volume    45 
11Author    G. Laskay, E. Lehoczki, A.L D Obi, L. SzalayRequires cookie*
 Title    Effects of Pyridazinone Herbicides during Chloroplast Development in Detached Barley Leaves III. Effects of SAN 6706 on Photosynthetic Activity and Chlorophyll-Protein Complexes  
 Abstract    Departm ent o f Biophysics, Jözsef A ttila U niversity, E gyetem u. 2 . The photosynthetic activities o f barley leaves in vivo and o f thylakoids, isolated from the leaves, in vitro were studied during greening in the presence or absence o f 2 x 10-4 m SA N 6706. The degree o f chlorophyll bleaching increased from 32% at 24 h o f greening to 60% at the final stage. Treated leaves were unable to carry out 14C 0 2-fixation, their fluorescence induction properties showed very lim ited, if any, photosystem II-activity, and the thylakoids isolated from the leaves were also inactive in m ediating ferricyanide H ill reaction. The leaves, how ever, exhibited light-induced quenching o f fluorescence revealed by slow fluorescence induction m easurem ents; and the thylakoids were active in m ediating photosystem I-specific in vitro M ehler reaction. Thylakoid membranes o f the chloroplasts isolated from treated leaves contained CP 1 and LH C P3 bands as revealed by polyacrylam ide gel electrophoresis. From these results it is concluded that i) greening in the presence o f SA N 6706 leads to the form ation o f inactive photosystem -II units; that ii) photosystem -I p e r se is active in vitro, and can, possibly, m ediate cyclic electron transport in vivo coupled to the formation o f A TP; and that iii) the presence o f xanthophyll pigm ents is required for the assembly o f the light-harvesting com plex. The experim ents were repeated with the application o f SA N 9789, another pyridazinone com ­ pound, and yielded practically the same results as those obtained with SA N 6706. For practical reasons, only the results obtained with SA N 6706 are dem onstrated throughout this com m unica­ tion. 
  Reference    Z. Naturforsch. 41c, 585—590 (1986); received February 3/March 17 1986 
  Published    1986 
  Keywords    SA N 6706, Electron Transport, F luorescence Induction 
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 TEI-XML for    default:Reihe_C/41/ZNC-1986-41c-0585.pdf 
 Identifier    ZNC-1986-41c-0585 
 Volume    41 
12Author    JaspreetA. Rora, P. V. SaneRequires cookie*
 Title    Histidyl Residues Mediate Electron Transport in Plant Mitochondria  
 Abstract    Plant The effect of chemical modification of histidyl residues using diethyl pyrocarbonate (D EP) on plant mitochondrial electron transport was studied. Mitochondrial membranes from potato tubers were isolated and electron flow from N A D H to oxygen, NADH to ferricyanide and ascorbate to oxygen were monitored in pro», nee and/or absence of DEP. Measurements were made at various concentrations of DEP and at different pHs either by using an oxygen electrode or spectro-photometrically. The results show that DEP inhibits flow of electrons from NADH to oxygen, however partial electron transport from N A D H to ferricyanide and ascorbate to oxygen was unaffected. Maximum inhibition was observed at pH 6.5. The time course of the DEP action revealed a biphasic nature of inhibition. Effects on the levels of reduction of cytochromes b and c by DEP during electron transport indicated that histidyl residues may be present before or at cytochrome b , which are being modified. 
  Reference    Z. Naturforsch. 44c, 537 (1989); received April 7 1989 D edicated to 
  Published    1989 
  Keywords    Mitochondria, Histidine Modification, Electron Transport, Spectral Studies 
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 TEI-XML for    default:Reihe_C/44/ZNC-1989-44c-0537.pdf 
 Identifier    ZNC-1989-44c-0537 
 Volume    44 
13Author    Salil Bose, R. M. Annar, M. Annan, C. J. ArntzenRequires cookie*
 Title    Increased Synthesis of Photosystem II in Triticum vulgare when Grown in the Presence of BAS 13-338  
 Abstract    Addition o f BAS 13-338 (4-chloro-5-dim ethylam ino-2-phenyl-3(2H)-pyridazinone) to a sus­ pension o f chloroplast thylakoids caused an increase in the / level o f chlorophyll fluorescence induction without affecting the F0 level and with a slight decrease in the Fmax level in a manner similar to the addition o f D C M U to a thylakoid suspension. A ddition o f BAS 13-338 also inhibited the rate o f Hill reaction H20 -» dichlorophenol indophenol with 50% inhibition occurring at about 10 hm BAS 13-338. The inhibition was not reversed by diphenyl carbazide used as an artificial electron donor to photosystem II. These results suggest that the site o f in h ib i­ tion by BAS 13-338 is between Q (next to the primary electron acceptor) and plastoquinone. When the plants were grown in the presence o f sublethal dose o f BAS 13-338, the follow ing changes were noted in the thylakoids o f the treated plants as com pared to the thylakoids isolated from the control plants: The F0 and the norm alized variable fluorescence (4F/F0) levels increased, chlorophyll a/b ratio decreased, chlorophyll/P 700 ratio increased. Furthermore, the rate o f photosystem II electron transport both under saturated intensity and the lim iting intensity of illumination increased, and the ratio o f plastoquinone to Q decreased. These observations have been interpreted as due to an increase in the ratio o f photosystem II to photosystem I in plants grown in the presence o f BAS 13-338. 
  Reference    Z. Naturforsch. 39c, 510 (1984); received D ecem ber 1 1983 
  Published    1984 
  Keywords    Photosynthesis, Electron Transport, Chlorophyll Fluorescence, Photosystem II, BAS 13-338 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0510.pdf 
 Identifier    ZNC-1984-39c-0510 
 Volume    39 
14Author    U. Hildebrand, K. Taraz, H. Budzikiewicz, H. Korth, G. PulvererRequires cookie*
 Title    Dicyano-bis(pyridin-2,6-dicarbothioato)-ferrat (II)/ferrat (III), ein weiteres eisenhaltiges Redoxsystem aus der Kulturlösung eines Pseudomonas-Stammes [11 D icyano-bis(pyridin-2,6-dicarbothioato)-ferrate (II)/ferrate (III), a Further Fe C ontaining R edox System from the Culture Medium o f Pseudomonas sp  
 Abstract    From the culture m edium o f Pseudomonas sp. a further Fe containing complex, viz. dicyano-bis(pyridin-2,6-dicarbothioato)-ferrate (III) (2) has been isolated which participates in a 
  Reference    Z. Naturforsch. 40c, 201—207 (1985); received D ecem ber 3 1984 
  Published    1985 
  Keywords    Redox System, Fe Com plex, Thio Acids, Electron Transport, Pseudomonas 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0201.pdf 
 Identifier    ZNC-1985-40c-0201 
 Volume    40 
15Author    Roland Pschorn, Wolfgang Rühle, Aloysius WildRequires cookie*
 Title    The Influence of the Proton Gradient on the Activation of Ferredoxin-NADP + -oxidoreductase by Light  
 Abstract    Ferredoxin-NADP + -oxidoreductase (FNR, EC 1.18.1.2) has been shown to be activated by light within a few seconds during dark-light transitions and inactivated in the dark. In previous papers this could be pointed out by the correlation of cytochrome /induction kinetics to the rate of NADP-photoreduction and the variable fluorescence. The present study deals with the role of the proton gradient during the activation process. The transition from an inactive to an active form is followed continuously in an in situ system. The steady-state rate of NADP-photoreduction is affected only by ionophores which inhibit a formation of the proton gradient, but not by inhibitors of the electric field. It correlates to the 9-aminoacridine fluorescence quench and the light scattering signals at 535 nm. The perception of the pH-gradient through the enzyme is still a matter of discussion. 
  Reference    Z. Naturforsch. 43c, 207—212 (1988); received December 28 1987 
  Published    1988 
  Keywords    Electron Transport, Ferredoxin-NADP + -oxidoreductase, Light Activation, Proton Gradient 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0207.pdf 
 Identifier    ZNC-1988-43c-0207 
 Volume    43 
16Author    U. H. Eber, J. Viil, S. Neimanis, T. Mimura, K.-J DietzRequires cookie*
 Title    Photoinhibitory Damage to Chloroplasts under Phosphate Deficiency and Alleviation of Deficiency and Damage by Photorespiratory Reactions  
 Abstract    D edicated to P rofessor A chim Trebst on the occasion o f his 60th birthday Effects of Pi deficiency on photosynthesis ot isolated spinach chloroplasts were examined. The following observations were made: (1) Chloroplasts isolated in Pi-free media evolved oxygen in the light in the absence of added Pi until acid-extractable P, in the chloroplasts had decreased to 1 to 2.5 m M . This Pj was unavailable for photophosphorylation as shown by the inability of the chloroplasts to respond by oxygen evolution to the addition of PGA. In the state of Prdeficiency, stromal ATP to A DP ratios were in the light close to or below ratios observed in the dark. In the presence of 2 mM PGA, addition of 20 (j.m Pi was insufficient to increase ATP to ADP ratios, but sufficient for appreciable oxygen evolution. (2) More Pi was available for oxygen evolution of phosphate-deficient chloroplasts at low levels of C 0 2 than at high levels. This was due mainly to the suppression of oxygenation of RuBP by high C 0 2 levels which prevented formation of phosphoglycolate and the subsequent release of Pi into the chloroplast stroma. (3) More oxygen was produced by phosphate-deficient chloroplasts at a low light intensity than at a high light intensity. This was due to increased availability of endogenous Pi under low light and to photoinhibition of the chloroplasts by high light. The main product of photosynthesis of phosphate-deficient chloroplasts in the presence of a high bicarbonate concentration was starch, and the main soluble product was PGA. (4) After phosphate-deficient chloroplasts had ceased to evolve oxygen in the light, they be­ came photosensitive. Part of the loss of the capacity for oxygen evolution is attributed to leakage of PGA, but the main reason for loss of function is photoinactivation of electron transport. Both photosystems of the electron transport chain were damaged by light. (5) Protection against photoinactivation was provided by coupled electron transport. Photo­ inactivation of phosphate-deficient chloroplasts was less extensive in the presence of low C 0 2 concentrations which permitted oxygenation of RuBP than at high CO: concentrations. Electron transport to C 0 2 and other physiological electron acceptors and to the herbicide methylviologen was also protective. However, electron transport to oxygen in the Mehler reaction failed to provide appreciable protection against high light intensities, because oxygen reduction is slow and reactive oxygen species produced in the light contribute to photoinactivation. 
  Reference    Z. Naturforsch. 44c, 524 (1989); received February 3 1989 
  Published    1989 
  Keywords    Photosynthesis, Photoinhibition, Photorespiration, Electron Transport, Phosphate Deficiency, Phosphate Homeostasis 
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 TEI-XML for    default:Reihe_C/44/ZNC-1989-44c-0524.pdf 
 Identifier    ZNC-1989-44c-0524 
 Volume    44 
17Author    KlausP B Ad Er, Judith SchülerRequires cookie*
 Title    Inhibition of the Photosynthetic Electron Transport by Pyrethroid Insecticides in Cell Cultures and Thylakoid Suspensions from Higher Plants  
 Abstract    Synthetic pyrethroid insecticides with different molecular structures have been investigated with respect to their effect on photosynthetic electron transport reactions in chloroplast sus­ pensions and cell cultures from higher plants. The fluorescence induction curves of tobacco (Nicotiana tabacum) leaves and tomato cells were substantially affected by permethrin and cypermethrin resulting in a strong increase of the maximum fluorescence. Application of different concentrations (0.3-1.2 m M) of the respective chemical abolishes virtually any ki­ netics of the normal Kautsky effect. Oxygen evolution from cell cultures from tomato (Ly-copersicon peruvianum) was completely inhibited by cypermethrin. Analysis of partial reac­ tions of the photosynthetic electron transport showed that both a methylviologen-mediated Mehler reaction and a ferricyanide-driven Hill reaction were quantitatively inhibited by e.g. fenvalerate. On the other hand, neither a silicomolybdate-driven Hill reaction nor a methylvi-ologen-driven Mehler reaction using dichlorophenol indophenol/ascorbate as electron donors could be inhibited by the pyrethroid. The analyses suggest that pyrethroid insecticides in­ terfere with the photosynthetic electron transport at the same site as urea-type herbicides do. Depending on the molecular structure and on the halogen compound in the molecule, however, different pyrethroids are more or less phytotoxic to the investigated photosynthetic membranes -cypermethrin with two Cl-substituents requires much higher concentrations to be applied for significant inhibition of the electron transport reactions than the Br-derivative deltamethrin does. Moreover, qualitative differences have to be taken into account. In the case of fenvalerate the effect seems to exist in a type of all-or-nothing reaction when the reaction centres are inhibited by the pyrethroid. None of the S-states nor the transition probabilities are specifically influenced by increasing concentrations of fenvalerate. In the case of deltamethrin, however, it was found that the overreduced state S_i is significantly increased at the expense of both Si and S(). Moreover, the miss parameter a is increased in the case of deltamethrin addition. The results and the significance of different substituents for the investigated pyrethroids are discussed. 
  Reference    Z. Naturforsch. 51c, 721—728 (1996); received April 25/June 20 1996 
  Published    1996 
  Keywords    Photosynthesis, Electron Transport, Oxygen Evolution, Pyrethroid Insecticide, Cell Culture 
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 TEI-XML for    default:Reihe_C/51/ZNC-1996-51c-0721.pdf 
 Identifier    ZNC-1996-51c-0721 
 Volume    51 
18Author    SujataR M Ishra, SurendraChandra SabatRequires cookie*
 Title    Effect of Magnesium and Calcium Ions on the Photoelectron Transport Activity of Low-Salt Suspended Hydrilla verticillata Thylakoids: Possible Sites of Cation Interaction  
 Abstract    Stimulatory effect o f divalent cations like calcium (Ca2+) and magnesium (M g2+) was inves­ tigated on electron transport activity of divalent cation deficient low-salt suspended (LS) thylakoid preparation from a submerged aquatic angiosperm, Hydrilla verticillata. Both the cations stimulated electron transport activity of LS-suspended thylakoids having an intact water oxidation complex. But in hydroxylamine (N H 2OH) -or alkaline Tris -washed thyla­ koid preparations (with the water oxidation enzyme impaired), only Ca2+ dependent stimula­ tion of electron transport activity was found. The apparent K m of Ca2+ dependent stimulation of electron flow from H 20 (endogenous) or from artificial electron donor (exogenous) to dichlorophenol indophenol (acceptor) was found to be identical. Calcium supported stimula­ tion of electron transport activity in N H 2OH -or Tris -washed thylakoids was electron donor selective, i.e., Ca2+ ion was only effective in electron flow with diphenylcarbazide but not with N H 2OH as electron donor to photosystem II. A magnesium effect was observed in thylakoids having an intact water oxidation complex and the ion became unacceptable in N H 2OH -or Tris -washed thylakoids. Indirect experimental evidences have been presented to suggest that Mg2+ interacts with the water oxidation complex, while the Ca2+ interaction is localized betw een Y z and reaction center of photosystem II. 
  Reference    Z. Naturforsch. 53c, 849—8 (1998); received March 16/May 12 1998 
  Published    1998 
  Keywords    Aquatic Angiosperm, Divalent Cation, Electron Transport, Fluorescence, Hydrilla verticillata 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0849.pdf 
 Identifier    ZNC-1998-53c-0849 
 Volume    53 
19Author    JeffA. Nemson, Anastasios MelisRequires cookie*
 Title    Light-Induced Oxidation-Reduction Reactions of Photosystem II in Dichlorophenyl-dimethyl Urea (DCM U) Inhibited Thylakoids  
 Abstract    Illumination o f thylakoid membranes in the presence o f 3-(3',4'-dichlorophenyl)-1,1-di-methyl urea (D C M U) causes the reduction o f the primary quinone acceptor QA o f photosys­ tem II (PS II) and the storage o f a positive charge on the donor side o f the photochem ical reac­ tion center. These oxidation-reduction reactions are accompanied by characteristic changes o f absorbance in the ultra-violet region o f the spectrum. The PS II-related absorbance difference spectra (2 5 0 -3 5 0 nm) were compared in control and hydroxylamine-treated thylakoid mem­ branes, and in thylakoids suspended in the presence o f carbonyl cyanide-/7-(trifluoromethoxy)-phenylhydrazone (FCCP). The light minus dark difference spectra were dominated by the QA minus QA difference spectrum. Qualitatively, the three spectra were identical in the 3 0 0 -3 5 0 nm region, however, they showed distinct differences in the 2 5 0 -3 0 0 nm region. The latter arose because o f different contributions from the donor side o f PS II in the thylakoid membrane o f the three samples. The result suggested that FCCP acts as the ultimate electron donor in D C M U -poisoned chloroplasts. Therefore, the absorbance difference spectrum in the presence o f FCCP reflected a contribution from the QA minus QA com ponent only. D econvolu­ tion o f the absorbance difference spectra o f control and hydroxylamine-treated thylakoids yielded difference spectra attributed to the oxidation o f a com ponent on the donor side o f PS II. This com ponent did not conform with the known M n(III) — ■ > M n(IV) transition. R ath­ er, it indicated the oxidation o f a modified form o f Mn in the presence o f D C M U , probably a Mn(II) —> M n(III) transition. The results are discussed in terms o f the use o f D C M U -poisoned thylakoid membranes in the quantitation o f the primary quinone acceptor Q A by spectro-photom etric approaches. 
  Reference    Z. Naturforsch. 45c, 258 (1990); received July 25/August 21. 1989 
  Published    1990 
  Keywords    Absorbance Difference Spectra, Photosystem II, Electron Transport, Primary Quinone Acceptor, Electron D onor Tyrosine 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0258.pdf 
 Identifier    ZNC-1990-45c-0258 
 Volume    45 
20Author    Jack Dekker, RonaldG. BurmesterRequires cookie*
 Title    Differential Pleiotropy in a psbA Gene Mutant of Brassica napus Implies Altered Temporal Photosynthesis and Thermal Tolerance  
 Abstract    Studies were conducted to test the hypothesis that the mutation to the psbA. plastid gene that confers s-triazine resistance (R) also results in an altered diurnal pattern o f photosynthetic car­ bon reduction (CER) relative to that o f the susceptible (S) wild-type. In all experiments CER approximated the increasing and decreasing light levels during the diurnal. S C ER exceeded that o f R during the midday period, but R CER was greater early and late in the diurnal at 25 °C. R CER exceeded that o f S for most o f the diurnal at 35 °C and in older, crowded, nitrogen-starved plants. These studies support the stated hypothesis and indicate a more complex model o f photosynthetic productivity than previously observed. An assessment o f the photosynthetic competence o f either biotype may be a function o f the time o f day or the environmental condi­ tions the plants are exposed to, especially temperature. 
  Reference    Z. Naturforsch. 45c, 474 (1990); received October 18 1989 
  Published    1990 
  Keywords    Photosystem II, D -l Protein, Electron Transport, C hronobiology, Diurnal Rhythms 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0474.pdf 
 Identifier    ZNC-1990-45c-0474 
 Volume    45 
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