Zum Einfluß verschieden substituierter s-Triazine auf Stoffwechselreaktionen der Grünalge Ankistrodesmus braunii / The Influence of Different s-Triazines on the Green Alga Ankistrodesmus braunii

1971 ◽  
Vol 26 (9) ◽  
pp. 919-921 ◽  
Author(s):  
Iris Rau ◽  
L. H. Grimme
Keyword(s):  
Electron Transport ◽  
Green Alga ◽  
Photosystem I ◽  
Light Reaction ◽  
Low Concentration

The effects of four different substituted s-Triazines (Ametryn, Atraton, Atrazin and Simazin) on growth, photosynthesis, respiration and photoreduction of the green alga Ankistrodesmus braunii were studied.The pl50-values ( = neg. log. of that concentration which produces 50% inhibition) for these reactions suggest a specific blocking of the second light reaction only in the very low concentration range of 10-6-10-7м. The most effective substance is Ametryn (p50(O2) =7.1) and the least effective Simazin (5.4).At higher concentrations there are inhibitions which seem to affect the electron transport rather than the photosystem I.

Superoxide-and Ethane-Formation in Subchloroplast Particles: Catalysis by Pyridinium Derivatives

1980 ◽  
Vol 35 (9-10) ◽  
pp. 770-775 ◽  
Author(s):  
E. F. Elstner ◽  
H. P. Fischer ◽  
W. Osswald ◽  
G. Kwiatkowski
Keyword(s):  
Electron Transport ◽  
Photosystem I ◽  
Photosynthetic Electron Transport ◽  
Redox Potentials ◽  
Light Reaction ◽  
Pyridinium Bromide ◽  
Superoxide Formation ◽  
Fatty Acid Peroxidation ◽  
Chlorophyll Bleaching ◽  
Ethane Formation

Abstract Oxygen reduction by chloroplast lamellae is catalyzed by low potential redox dyes with E′0 values between -0 .3 8 V and -0 .6 V. Compounds of E′0 values of -0 .6 7 V and lower are inactive. In subchloroplast particles with an active photosystem I but devoid of photosynthetic electron transport between the two photosystems, the active redox compounds enhance chlorophyll bleaching, superoxide formation and ethane production independent on exogenous substrates or electron donors. The activities of these compounds decrease with decreasing redox potential, with one exception: 1-methyl-4,4′-bipyridini urn bromide with an E′0 value of lower -1 V (and thus no electron acceptor of photosystem I in chloroplast lamellae with intact electron transport) stimulates light dependent superoxide formation and unsaturated fatty acid peroxidation in sub­ chloroplast particles, maximal rates appearing after almost complete chlorophyll bleaching. Since this activity is not visible with compounds with redox potentials below -0 .6 V lacking the nitrogen atom at the 1-position of the pyridinium substituent, we assume that 1 -methyl-4,4′-bi-pyridinium bromide is “activated” by a yet unknown light reaction.

Stoichiometric Photophosphorylation in Thylakoids from the Blue-Green Alga, Anabaena variabilis

1980 ◽  
Vol 35 (1-2) ◽  
pp. 98-105 ◽  
Author(s):  
Erika Wax ◽  
Wolfgang Lockau
Keyword(s):  
Electron Transport ◽  
Green Alga ◽  
Photosystem I ◽  
Electron Transport Chain ◽  
Photosynthetic Electron Transport ◽  
Anabaena Variabilis ◽  
Blue Green Alga ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain ◽  
Photosynthetic Control

Abstract A method is described for the preparation of thylakoids from the blue-green alga Anabaena variabilis which exhibit photosynthetic control. The thylakoids can be stored in liquid N 2 with little loss in activity. P/e2 ratios (num ber of ATP molecules formed per pair of electrons transported) have been determined for partial reactions of the photosynthetic electron transport chain. Electron transport from water to an electron acceptor of photosystem I is coupled to phosphorylation with a P/e2 ratio of 0.9-1.2, from water to electron acceptors of photosystem II with ratios of 0.21-0.3 , and oxidations of hydrogen carriers by photosystem I with ratios of 0.3-0.35. Electron transport in these assay systems generates a proton gradient across the thylakoid membrane (acid inside), which is decreased by the substrates of phosphorylation and by uncouplers.

Effects of Diphenylether Herbicides on Reactions of Mitochondria and Chloroplasts

Weed Science ◽  
1970 ◽  
Vol 18 (5) ◽  
pp. 636-642 ◽  
Author(s):  
D. E. Moreland ◽  
W. J. Blackmon ◽  
H. G. Todd ◽  
F. S. Farmer
Keyword(s):  
Electron Transport ◽  
Oxygen Uptake ◽  
Spinacia Oleracea ◽  
White Potato ◽  
Light Reaction ◽  
Site Of Action ◽  
Transport Inhibitors ◽  
Atp Generation ◽  
A Site ◽  
Limited Oxygen

Effects of three diphenylether herbicides [2,4-dichlorophenyl-p-nitrophenyl ether (nitrofen); 2,4,6-trichlorophenyl-4′-nitrophenyl ether (hereinafter referred to as MC-1478); and 2,4′-dinitro-4-trifluoromethyl-diphenylether (hereinafter referred to as C-6989)] were measured on phosphorylation and electron transport in spinach(Spinacia oleraceaL.) chloroplasts, and mung bean(Phaseolus aureusL., var. Jumbo) and white potato tuber(Solarium tuberosumL.) mitochondria. All of the diphenylethers acted primarily as inhibitors of chloroplast noncyclic electron transport, and the coupled photophosphorylation. The compounds ranked in the following decreasing order of inhibitory effectiveness: MC-1478 ≥ C-6989 >> nitrofen. A site of action close to light reaction II was suggested. At high molar concentrations, marginal interference with cyclic electron transport or phosphorylation was obtained. In mitochondria, MC-1478 and nitrofen acted primarily as electron transport inhibitors with malate, NADH, and succinate as substrates. MC-1478 was a slightly stronger inhibitor than nitrofen. Only slight stimulation of ADP-limited oxygen uptake was obtained during the oxidation of NADH and succinate; whereas, strong inhibition of oxygen uptake was obtained with malate. C-6989 also weakly stimulated ADP-limited oxygen uptake with NADH and succinate but differed from the two chlorinated diphenylethers in that electron transport was not inhibited when ADP was present in excess. Interference with ATP generation could be one of the mechanisms through which the phytotoxicity of diphenylether herbicides is expressed.

Photoinhibition of Electron Transport Activity of Photosystem II in Isolated Thylakoids Studied by Thermoluminescence and Delayed Luminescence

1988 ◽  
Vol 43 (11-12) ◽  
pp. 871-876 ◽  
Author(s):  
Imre Vass ◽  
Narendranath Mohanty ◽  
Sándor Demeter
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Half Life ◽  
Delayed Luminescence ◽  
Transport Activity ◽  
Primary Target ◽  
Electron Transport Activity ◽  
The Stability ◽  
Spinach Thylakoids

Abstract The effect of photoinhibition on the primary (QA) and secondary (QB) quinone acceptors of photosystem I I was investigated in isolated spinach thylakoids by the methods of thermoluminescence and delayed luminescence. The amplitudes of the Q (at about 2 °C) and B (at about 30 °C) thermoluminescence bands which are associated with the recombination of the S2QA- and S2QB charge pairs, respectively, exhibited parallel decay courses during photoinhibitory treatment. Similarly, the amplitudes of the flash-induced delayed luminescence components ascribed to the recombination of S20A and S2OB charge pairs and having half life-times of about 3 s and 30 s, respectively, declined in parallel with the amplitudes of the corresponding Q and B thermoluminescence bands. The course of inhibition of thermoluminescence and delayed luminescence intensity was parallel with that of the rate of oxygen evolution. The peak positions of the B and Q thermoluminescence bands as well as the half life-times of the corresponding delayed luminescence components were not affected by photoinhibition. These results indicate that in isolated thylakoids neither the amount nor the stability of the reduced OB acceptor is preferentially decreased by photoinhibition. We conclude that either the primary target of photodamage is located before the O b binding site in the reaction center of photosystem II or QA and OB undergo simultaneous damage.

scholarly journals Flavodiiron proteins act as safety valve for electrons in Physcomitrella patens

2016 ◽  
Vol 113 (43) ◽  
pp. 12322-12327 ◽  
Author(s):  
Caterina Gerotto ◽  
Alessandro Alboresi ◽  
Andrea Meneghesso ◽  
Martina Jokel ◽  
Marjaana Suorsa ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem I ◽  
Physcomitrella Patens ◽  
Safety Valve ◽  
Cell Metabolism ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Electron Transport ◽  
Flowering Plants ◽  
Knock Out ◽  
Electron Sink

Photosynthetic organisms support cell metabolism by harvesting sunlight to fuel the photosynthetic electron transport. The flow of excitation energy and electrons in the photosynthetic apparatus needs to be continuously modulated to respond to dynamics of environmental conditions, and Flavodiiron (FLV) proteins are seminal components of this regulatory machinery in cyanobacteria. FLVs were lost during evolution by flowering plants, but are still present in nonvascular plants such as Physcomitrella patens. We generated P. patens mutants depleted in FLV proteins, showing their function as an electron sink downstream of photosystem I for the first seconds after a change in light intensity. flv knock-out plants showed impaired growth and photosystem I photoinhibition when exposed to fluctuating light, demonstrating FLV’s biological role as a safety valve from excess electrons on illumination changes. The lack of FLVs was partially compensated for by an increased cyclic electron transport, suggesting that in flowering plants, the FLV’s role was taken by other alternative electron routes.

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