Differential Solubilization of the Integral Electron Transport Complexes from the Thylakoid Membrane of Spinach Chloroplasts. Localization of Photosystem I, Photosystem II and the Cytochrome B6-F Complex

Highly characteristic responses of thylakoid membranes were observed in function and composition when fully developed plants of Amaranthus hypochondriacus L. grown under light sufficient (2000 μmol m-2 s-1) conditions were transferred to light limited conditions (650 μmol m-2 s-1 and 200 μmol m-2 s-1). The whole-chain, photosystem I and photosystem II electron transport rates were depressed in both bundle sheath and mesophyll thylakoids with remarkable differences between them in variation of rates under limiting light. The reduction in PSI electron transport in the mesophyll could be attributed to reduced PSI centres, while in the bundle sheath, a modulation of cytochrome b6/f complex regulated the rates of PSI electron transport. The requirement for an unaltered number of PSI centres under limiting light in the bundle sheath is ascribed to operation of an energy-consuming C4 pump.

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LIGHT-ABSORPTION AND ELECTRON-TRANSPORT BALANCE BETWEEN PHOTOSYSTEM II AND PHOTOSYSTEM I IN SPINACH CHLOROPLASTS

Photochemistry and Photobiology ◽

10.1111/j.1751-1097.1987.tb08413.x ◽

1987 ◽

Vol 45 (1) ◽

pp. 129-136 ◽

Cited By ~ 94

Author(s):

Anastasios MELIS ◽

Michael Spangfort ◽

Bertil Andersson

Keyword(s):

Electron Transport ◽

Photosystem Ii ◽

Photosystem I ◽

Light Absorption ◽

Spinach Chloroplasts

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The effect of alpha terthienyl on photosynthesis

Canadian Journal of Botany ◽

10.1139/b82-311 ◽

1982 ◽

Vol 60 (12) ◽

pp. 2565-2569 ◽

Cited By ~ 6

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.

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

Zeitschrift für Naturforschung C ◽

10.1515/znc-1988-11-1213 ◽

1988 ◽

Vol 43 (11-12) ◽

pp. 871-876 ◽

Cited By ~ 35

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.

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