Measurement of the relative electron-transport capacity of Photosystem I and Photosystem II in spinach chloroplasts

1984 ◽  
Vol 765 (2) ◽  
pp. 186-195 ◽  
Author(s):  
S.W. McCauley ◽  
S.E. Taylor ◽  
R.J. Dennenberg ◽  
A. Melis
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Transport Capacity ◽  
Spinach Chloroplasts ◽  
Relative Electron

Stimulation of electron transport from Photosystem II to Photosystem I in spinach chloroplasts

1980 ◽  
Vol 12 (3-4) ◽  
pp. 197-203 ◽  
Author(s):  
Rita Barr ◽  
Randa Melhem ◽  
Anne L. Lezotte ◽  
Frederick L. Crane
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Spinach Chloroplasts ◽  
Stimulation Of

The effect of alpha terthienyl on photosynthesis

1982 ◽  
Vol 60 (12) ◽  
pp. 2565-2569 ◽  
Author(s):  
John Sinclair ◽  
Thor Arnason
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Electron Acceptor ◽  
Hill Reaction ◽  
Spinach Chloroplasts ◽  
Near Ultraviolet ◽  
A Site ◽  
The Hill ◽  
Clark Electrode

Alpha terthienyl (α-T), an allelopathic polyacetylene derivative occurring in the Asteraceae, was examined for its photosensitizing effect on respiration in Chlorella and photosynthesis in Chlorella and isolated spinach chloroplasts. In experiments with the Clark electrode, O2 evolution in saturating light with Chlorella was much more sensitive to α-T plus near ultraviolet (UV) treatments than respiration. O2 transients at the onset of illumination as measured with the modulated O2 polarograph were also inhibited by α-T plus near UV. The Hill reaction in uncoupled spinach chloroplasts using ferricyanide as electron acceptor is sensitive to photosensitization with α-T, but electron transport through photosystem I operating on its own showed no decrease in activity. The results are interpreted as an indication of a site of inhibition near photosystem II and possibly in CO2 fixation as well.

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.

DCMU-Induced Fluorescence Changes and Photodestruction of Pigments Associated with an Inhibition of Photosystem I Cyclic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 351-353 ◽  
Author(s):  
Stuart M. Ridley ◽  
Peter Horton
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Dose Response ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Cyclic Flow ◽  
Working Hypothesis ◽  
Dose Responses

Diuron (DCMU) induces the photodestruction of pigments, which is the initial herbicidal symptom. As a working hypothesis, it is proposed that this symptom can only be produced when the herbicide dose is sufficiently high to inhibit not only photosystem II electron transport almost completely, but also inhibit (through over oxidation) the natural cyclic electron flow associated with photosystem I as well. Using freshly prepared chloroplasts, studies of DCMU-induced fluorescence changes, and dose responses for inhibition of electron transport, have been compared with a dose response for the photodestruction of pigments in chloroplasts during 24 h illumination. Photodestruction of pigments coincides with the inhibition of cyclic flow.

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