Investigations on a Galvanic Cell Driven by Photosynthetic Electron Transport

1978 ◽  
Vol 33 (5-6) ◽  
pp. 392-401 ◽  
Author(s):  
Wolfgang Haehnel ◽  
Adelheid Heupel ◽  
Dorothea Hengstermann
Keyword(s):  
Electron Transport ◽  
Open Circuit Potential ◽  
Photosynthetic Activity ◽  
Photosynthetic Electron Transport ◽  
Open Circuit ◽  
Galvanic Cell ◽  
Platinum Electrodes ◽  
High Effectiveness ◽  
Electron Carriers ◽  
Isolated Chloroplasts

Abstract A light-driven galvanic cell was constructed making use of the photosynthetic activity of isolated chloroplasts. Artificial mediators managed the transfer of electrons from the endogenous electron carriers to the platinum electrodes in each of the joined half-cells. In one the mediators were reduced by electrons originating from water. In the other the mediators were oxidized by photosystem I in the presence of an autoxidizable electron acceptor. The redox potential in the single half-cells has been studied as a function of the lipophilicity of the mediators and their concentration. Further­ more different autoxidizable acceptors and different treatments of the chloroplasts were investigated. The combined half-cells were separated by an ultrafiltration membrane. Upon illumination the system gave rise to an open circuit potential of up to 220 mV. This battery was charged with rates as high as photosynthetic electron transport rates. The results are discussed with respect to the arrangement of the cell and the properties of the components for high effectiveness and maximal potential differences.

scholarly journals Plastocyanin is the long-range electron carrier between photosystem II and photosystem I in plants

2020 ◽  
Vol 117 (26) ◽  
pp. 15354-15362 ◽  
Author(s):  
Ricarda Höhner ◽  
Mathias Pribil ◽  
Miroslava Herbstová ◽  
Laura Susanna Lopez ◽  
Hans-Henning Kunz ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Long Range ◽  
Narrow Range ◽  
Higher Plants ◽  
Regulatory Element ◽  
Photosynthetic Electron Transport ◽  
Electron Carrier ◽  
Mobile Electron ◽  
Electron Carriers

In photosynthetic electron transport, large multiprotein complexes are connected by small diffusible electron carriers, the mobility of which is challenged by macromolecular crowding. For thylakoid membranes of higher plants, a long-standing question has been which of the two mobile electron carriers, plastoquinone or plastocyanin, mediates electron transport from stacked grana thylakoids where photosystem II (PSII) is localized to distant unstacked regions of the thylakoids that harbor PSI. Here, we confirm that plastocyanin is the long-range electron carrier by employing mutants with different grana diameters. Furthermore, our results explain why higher plants have a narrow range of grana diameters since a larger diffusion distance for plastocyanin would jeopardize the efficiency of electron transport. In the light of recent findings that the lumen of thylakoids, which forms the diffusion space of plastocyanin, undergoes dynamic swelling/shrinkage, this study demonstrates that plastocyanin diffusion is a crucial regulatory element of plant photosynthetic electron transport.

Effects of N,N′-Dibutylurea on Photosynthetic Electron Transport Reactions in Isolated Chloroplasts

1998 ◽  
Vol 59 (3) ◽  
pp. 129-135 ◽  
Author(s):  
R. Querns ◽  
G.E. MacDonald ◽  
J.F. Gaffney ◽  
C.A. Chase ◽  
H.A. Moye ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Isolated Chloroplasts

Counteraction of Paraquat Toxicity at the Chloroplast Level

1987 ◽  
Vol 42 (7-8) ◽  
pp. 824-828 ◽  
Author(s):  
Brad L. Upham ◽  
Kriton K. Hatzios
Keyword(s):  
Electron Transport ◽  
Pisum Sativum ◽  
Photosynthetic Electron Transport ◽  
Heme Iron ◽  
Hill Reaction ◽  
Ion Toxicity ◽  
Plastoquinone Pool ◽  
Pisum Sativum L ◽  
Paraquat Toxicity ◽  
Isolated Chloroplasts

Six pyridyl derivatives [benzylviologen, 2-anilinopyridine, 1,2-bis(4-pyridyl)ethane, 1,2-bis(4- pyridyl)ethylene, 2-benzoylpyridine, and 2-benzylaminopyridine] and five heme-iron derivatives [hemoglobin, hemin, hematin, ferritin, and ferrocene] were screened for their potential to coun- teract paraquat (1,1′-dimethyl-4.4′-bipyridinium ion) toxicity on pea (Pisum sativum L.) isolated chloroplasts. The H2O -> methylviologen(MV)/O2 and H2O → ferredoxin(Fd)/NADP+ were two Hill reactions assayed with these compounds. Antagonists of paraquat toxicity should inhibit the first Hill reaction but not the latter. All pyridyl derivatives examined did not inhibit the reaction H2O → MV/O2. Ferritin and ferrocene were also ineffective as inhibitors of this reaction. Hemoglobin inhibited the reaction H2O → MV/O2 without inhibiting the reaction H2O → Fd/NADP+, providing protection to pea chloroplasts against paraquat. Hemin and hematin inhibited both Hill reactions examined. They also inhibited H2O → diaminodurene(DAD)ox and durohydro-quinone → MV/O2 Hill reactions but not the dichlorophenol indophenolred → MV/O2 and DADred → MV/O2 Hill reactions. These results suggest that hemin and hematin are inhibiting the photosynthetic electron transport in the plastoquinone-pool region.

The site of electron transport inhibition by bentazon (3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide) in isolated chloroplasts

1982 ◽  
Vol 60 (4) ◽  
pp. 409-412 ◽  
Author(s):  
Rungsit Suwanketnikom ◽  
Kriton K. Hatzios ◽  
Donald Penner ◽  
Duncan Bell
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Electron Acceptor ◽  
Photosynthetic Electron Transport ◽  
Primary Electron ◽  
Photochemical Reactions ◽  
Spinacea Oleracea ◽  
Primary Electron Acceptor ◽  
Isolated Chloroplasts

The effect of bentazon (3-isopropyl-1H-2,1,3-benzathiadiazin-(4)3H-one 2,2-dioxide) on various photochemical reactions of isolated spinach (Spinacea oleracea L.) chloroplasts was studied at concentrations 0, 5, 15, 45, and 135 μM. Bentazon at a concentration of 135 μM strongly inhibited uncoupled electron transport from water to ferricyanide or to methylviologen with inhibition percentages greater than 90%. Photosystem II mediated electron transport from water to oxidized diaminodurene, with 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) blocking photosystem I, was also strongly inhibited by bentazon at 135 μM but less with lower concentrations of bentazon. Photosystem I mediated transfer of electrons from diaminodurene to methylviologen, with 3,4-dichlorophenyl-1,1-dimethylurea (DCMU) blocking photosystem II, was not inhibited by bentazon at any concentration examined. Transfer of electrons from catechol to methylviologen in hydroxylamine-treated chloroplasts was inhibited by bentazon, and the inhibition percentages were again concentration dependent. The data indicate that the site of bentazon inhibition of the photosynthetic electron transport is at the reducing side of photosystem II, between the primary electron acceptor Q and plastoquinone.

Inhibition of Photosynthetic Electron Transport by Azaphenanthrenes

1974 ◽  
Vol 29 (9-10) ◽  
pp. 545-551 ◽  
Author(s):  
Walter Oettmeier ◽  
Rolf Grewe
Keyword(s):  
Electron Transport ◽  
Mechanism Of Action ◽  
Inhibitory Activity ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Iron Complexes ◽  
Lower Activity ◽  
Photosynthetic Electron Flow ◽  
Isolated Chloroplasts ◽  
Insight Into

Abstract Various mono-and diazaphenanthrenes were prepared and assayed for their activity as inhibi­tors of photosynthetic electron flow in isolated chloroplasts in order to get more insight into the mechanism of action of the well known inhibitor o-phenanthroline = 1,10-diazaphenanthrene. The results show that 1-, 4-and 5-azaphenanthrene are only slightly less active than 1,10-diazaphen-anthrene. In the case of the different diazaphenanthrenes, 1,4-, 1,7-and 5,6-diazaphenanthrene exhibited somewhat lower activity than 1,10-diaphenanthrene, whereas 2,9-and 4,7-diazaphen-anthrene were completely inactive. Substitution at C-atoms of 1,10-diazaphenanthrene leads to an increase in activity in the case of the 4-and 7-position, regardless of electropositive or electro­ negative substituents, whereas substitution at the 2-, 3-, 5-, 6-, 8-and 9-position leads to a de­ creased activity. The ability of 1,10-diazaphenanthrene to form iron complexes seems to be of little relevance to the inhibitory activity on photosynthetic electron transport. This follows also from the fact that other strong iron complexing agens, like 2.2'-bipyridine or 8-hydroxyquinoline, are not inhibitory

On a new inhibitor of photosynthetic electron-transport in isolated chloroplasts

1970 ◽  
Vol 25 (10) ◽  
pp. 1157-1159 ◽  
Author(s):  
A. Trebst ◽  
E. Harth ◽  
W. Draber
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
High Concentration ◽  
Ferricyanide Reduction ◽  
The Hill ◽  
Photosystem I And Ii ◽  
Isolated Chloroplasts

A halogenated benzoquinone has been found to inhibit the photosynthetic electron transport system in isolated chloroplasts. 2·10-6ᴍ of dibromo-thymoquinone inhibit the Hill- reaction with NADP, methylviologen or anthraquinone to 100%, but do not effect the photoreduction of NADP at the expense of an artificial electron donor. The Hill - reaction with ferricyanide is inhibited even at the high concentration of 2·10-5ᴍ of dibromo-thymoquinone to only 60%. The remaining reduction in the presence of the inhibitor reflects the rate of ferricyanide reduction by photosystem II. It is concluded that the inhibition of electron transport by the quinone occurs between photosystem I and II and close to or at the functional site of plastoquinone.

scholarly journals The Cupric Ion as an Inhibitor of Photosynthetic Electron Transport in Isolated Chloroplasts

1972 ◽  
Vol 50 (6) ◽  
pp. 698-701 ◽  
Author(s):  
Arturo Cedeno-Maldonado ◽  
J. A. Swader ◽  
Robert L. Heath
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Cupric Ion ◽  
Isolated Chloroplasts

Effects of Pyridate on Chickpea

1995 ◽  
Vol 22 (5) ◽  
pp. 731 ◽  
Author(s):  
R Gimeenez-Espinosa ◽  
R Jimenez-Diaz ◽  
RD Prado
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Fluorescence Intensity ◽  
Active Ingredient ◽  
Photosynthetic Activity ◽  
Photosynthetic Electron Transport ◽  
Fluorescence Induction ◽  
Hill Reaction ◽  
Lolium Rigidum ◽  
Cicer Arietinum L

The effects of pyridate on 15 different chickpea (Cicer arietinum L.) genotypes have been investigated under controlled environmental conditions. Different degrees of tolerance to pyridate were detected. Pyridate applied at 2.0 and 4.0 kg active ingredient ha-1 inhibited the growth of two of the 15 genotypes. Chlorophyll fluorescence intensity showed high levels of inhibition 3 h after treatment in chickpea. For all the genotypes, photosynthetic activity was recovered 10 days after treatment. Fluorescence-induction curves revealed that pyridate inhibited photosynthetic electron transport in chickpea genotypes and Amaranthus blitoides faster than in Lolium rigidum. Photosynthesis in chickpea genotypes recovered more quickly than in Lolium rigidum, while Amaranthus blitoides died 3 days after treatment. Hill reaction assays concluded that CL9673 was the most phytotoxic pyridate metabolite. The order of phytotoxicity was CL9673 >> CL9673-N-Gly > CL9869 > pyridate > CL9673-O-Gly. These results support the idea that tolerance of chickpea to pyridate is due to degradation and detoxification of the herbicide.

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