Comparison of Photosystem II Electron Transport and Oxygen Evolution in Two Marine Algae

1994 ◽  
pp. 427-429
Author(s):  
C. Geel ◽  
J. F. H. Snel
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Oxygen Evolution ◽  
Marine Algae

Inhibition of oxygen evolution by ivalin

1994 ◽  
Vol 72 (2) ◽  
pp. 177-181 ◽  
Author(s):  
Ernesto Bernal-Morales ◽  
Alfonso Romo De Vivar ◽  
Bertha Sanchez ◽  
Martha Aguilar ◽  
Blas Lotina-Hennsen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Sesquiterpene Lactone ◽  
Oxygen Evolution ◽  
Electron Flow ◽  
Atp Synthesis ◽  
Naturally Occurring ◽  
Transport Inhibitor ◽  
Proton Uptake ◽  
Key Words Oxygen

The inhibition of ATP synthesis, proton uptake, and electron transport (basal, phosphorylating, and uncoupled) from water to methylviologen by ivalin (a naturally occurring sesquiterpene lactone in Zaluzania triloba and Iva microcephala) indicates that it acts as electron transport inhibitor. Since photosystem I and electron transport from DPC to QA were not affected, while the electron flow of uncoupled photosystem II from H2O to DAD and from water to silicomolybdate was inhibited, we concluded that the site of inhibition of ivalin is located at the oxygen evolution level. Key words: oxygen evolution, ivalin, photosynthesis, sesquiterpene lactone.

Involvement of the Xanthophyll Cycle in Regulation of Cyclic Electron Flow around Photosystem II

1996 ◽  
Vol 51 (1-2) ◽  
pp. 47-52 ◽  
Author(s):  
W. I. Gruszecki ◽  
K. Strzałk ◽  
K.P. Bader ◽  
A. Radunz ◽  
G.H. Schmid
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Oxygen Evolution ◽  
Xanthophyll Cycle ◽  
Electron Flow ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Oxygen Evolution ◽  
Cyclic Electron Transport ◽  
Ps Ii ◽  
Low Levels

Abstract In our previous study (Gruszecki et al., 1995) we have postulated that the mechanism of cyclic electron transport around photosystem II, active under overexcitation of the photosynthetic apparatus by light is under control of the xanthophyll cycle. The combination of dif­ferent light quality and thylakoids having various levels of xanthophyll cycle pigments were applied to support this hypothesis. In the present work photosynthetic oxygen evolution from isolated tobacco chloroplasts was measured by means of mass spectrometry under conditions of high or low levels of violaxanthin, being transformed to zeaxanthin during dark incubation in an ascorbate containing buffer at pH 5.7. Analysis of oxygen evolution and of light-induced oxygen uptake indicate that the de-epoxidation of violaxanthin to zeaxanthin results in an increased cyclic electron transport around PS II, thus dimishing the vectorial electron flow from water. An effect similar to de-epoxidation was observed after incubation of thylakoid membranes with specific antibodies against violaxanthin.

Herbicides which Inhibit Electron Transport or Produce Chlorosis and Their Effect on Chloroplast Development in Radish Seedlings I. Chlorophyll a Fluorescence Transients and Photosystem II Activity

1982 ◽  
Vol 37 (3-4) ◽  
pp. 268-275 ◽  
Author(s):  
K. H. Grumbach
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Chlorophyll A ◽  
Oxygen Evolution ◽  
Chlorophyll A Fluorescence ◽  
Photosynthetic Electron Transport ◽  
Photosystem Ii Activity ◽  
Chlorophyll A Fluorescence Transients ◽  
Radish Seedlings ◽  
Fluorescence Transients

Abstract Diuron and bentazon are very strong inhibitors of the photosynthetic electron transport in isolated radish chloroplasts. The chlorosis producing herbicide SAN 6706 also inhibited the photosystem II dependent oxygen evolution. Aminotriazole had no effect. The inhibitor concentration for 50% inhibition of photosystem II activity was 10-7 m for diuron and 10-4 m for bentazon and SAN 6706 respectively.Diuron and bentazon quenched the chlorophyll a fluorescence transients in isolated radish chloroplasts drastically, while aminotriazole was not effective. It was of particular interest that the bleaching herbicide SAN 6706 inhibited photosystem II dependent oxygen evolution in a similar concentration as bentazon but had no effect on the chlorophyll a-fluorescence transients suggesting that SAN 6706 is not binding to the same site of the electron transport chain as diuron and bentazon.Apart from their direct influence on electron transport in isolated photosynthetically active chloroplasts the photosystem II and bleaching herbicides assayed also strongly affected photosynthesis in radish seedlings that were grown in the presence of the herbicides for a long time. As already obtained using isolated chloroplasts, photosystem II dependent oxygen evolution like the chlorophyll a fluorescence transients were strongly inhibited by the photosystem II herbicides diuron and bentazon. A reduction but no inhibition of photosystem II activity was observed in plants that were grown in the presence of aminotriazole. The pyridazinone SAN 6706 was behaving contradictory. In partly green plants photosystem II activity was still maintained and even higher than in untreated plants while in albinistic plants no photosynthetic activity was detected.

Antagonistic Effects of α-Tocopherol and α-Tocoquinone in the Regulation of Cyclic Electron Transport around Photosystem II

1997 ◽  
Vol 52 (11-12) ◽  
pp. 766-774 ◽  
Author(s):  
J. Kruk ◽  
K. Burda ◽  
A. Radunz ◽  
K. Strzałka ◽  
G. H. Schmid
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Oxygen Evolution ◽  
Transition Probability ◽  
Continuous Illumination ◽  
Oxygen Evolving Complex ◽  
Cyclic Electron Transport ◽  
State Distribution ◽  
Ps Ii ◽  
Oxygen Evolving

Abstract α-Tocoquinone (α-TQ ) and α-tocopherol (α-TOC) which cannot substitute for plastoquinone-9 (PQ-A) as an electron acceptor from photosystem II (PS II), influence the oxygen evolution activity of thylakoid membranes under continuous illumination. In the presence of the herbicide DCMU and the protonophore FCCP which stimulate cyclic electron transport around PS II, α-TQ decreased oxygen evolution whereas α-TOC enhanced it. The effects are attributed to a stimulation or an inhibition of cyclic electron transport around PS II by α-TQ and α-TOC, respectively. Results of flash light experiments on PS II preparations show that both α-TQ and α-TOC increased the d-parameter which describes the transition probability from the S3- to the S0-state of the oxygen-evolving complex, although to a smaller extent when PQ-A is added alone to the preparations. The initial S-state distribution in darkadapted samples was changed only upon PQ-A addition and influenced neither by α-TQ nor by α-TO C supplementation. These effects indicate different kinds of interaction of PQ-A, α-TQ and α-TOC with the PS II components. α-TQ increased and α-TOC decreased the “total miss” parameter both in the presence or absence of PQ-A. A possible site of interaction of α-TQ and α-TO C with the cyclic electron transport around PS II is suggested.

Effect of α- and β-cyclodextrins on the photochemical activity of thylakoid membranes and photosystem II particles from barley (Hordeum vulgare): oxygen evolution and whole chain electron transport

2005 ◽  
Vol 83 (3) ◽  
pp. 320-328 ◽  
Author(s):  
S Dudekula ◽  
G Sridharan ◽  
M Fragata
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Hordeum Vulgare ◽  
Photosystem Ii ◽  
Oxygen Evolution ◽  
Thylakoid Membranes ◽  
Photochemical Activity ◽  
Nonlinear Dependence ◽  
Hordeum Vulgare L ◽  
Sigmoidal Curve

The effect of α- and β-cyclodextrin (CD) concentration (0–16 mM) on oxygen evolution in photosystem II (PSII) and whole chain electron transport (H2O to photosystem I (PSI)) was studied in isolated thylakoid membranes and PSII particles from barley (Hordeum vulgare L.). The CDs are cyclic oligosaccharides containing, for example, six (α-CD) or seven (β-CD) α-D-glucose residues linked by α-1,4 glycosidic bonds. These compounds alter the lipid composition of the thylakoids and most likely also the structure of their membrane proteins. We show for the first time that in the thylakoid membranes, but not in the isolated PSII particles, the relationship between oxygen evolution in PSII and the CD concentration is represented by a S-shaped (sigmoidal) curve displaying a sharp inflexion point or transition. We found, in addition, that the CDs inhibit the whole chain electron transport from H2O to methyl viologen, that is, PSI, measured as oxygen uptake, according to a nonlinear dependence that is also sigmoidal. Moreover, another interesting observation is that in the thylakoid membranes the electron transport from H2O to PSI is quite well inhibited at low CD concentrations (<4–6 mM), whereas the oxygen evolution in PSII is only substantially enhanced at CD concentrations greater than 8–10 mM. To explain this, we suggest that the mechanisms underlying the inhibition of electron transfer from H2O to PSI become operative before those giving origin to the enhancement of oxygen evolution in PSII.Key words: cyclodextrins, electron transfer, nonlinearity, oxygen evolution, photosystem, thylakoid membrane.

Blue Light-Enhanced Photosynthetic Oxygen Evolution from Liposome-Bound Photosystem II Particles; Possible Role of the Xanthophyll Cycle in the Regulation of Cyclic Electron Flow Around Photosystem II?

1995 ◽  
Vol 50 (1-2) ◽  
pp. 61-68 ◽  
Author(s):  
W. I. Gruszecki ◽  
K. Strzałka ◽  
A. Radunz ◽  
J. Kruk ◽  
G. H. Schmid
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Oxygen Evolution ◽  
Xanthophyll Cycle ◽  
Red Light ◽  
Photosynthetic Oxygen Evolution ◽  
Reaction Centre ◽  
Ps Ii ◽  
Photosynthetic Oxygen ◽  
Β Carotene

Abstract Light-driven electron transport in liposome-bound photosystem II (PS-II) particles be­tween water and ferricyanide was monitored by bare platinum electrode oxymetry. The modi­fication of the experimental system with the exogenous quinones α-tocopherol quinone ( α-TQ) or plastoquinone (PQ) resulted in a pronounced effect on photosynthetic oxygen evolution. The presence of α-tocopherolquinone ( α-TQ) in PS-II samples decreased the rate of red light-induced oxygen evolution but increased the rate of green light-induced oxygen evolution. Blue light applied to the assay system in which oxygen evolution was saturated by red light resulted in a further increase of the oxygen signal. These findings are interpreted in terms of a cyclic electron transport around PS-II, regulated by an excitation state of β-carotene in the reaction centre of PS-II. A mechanism is postulated according to which energetic coupling of β-carotene in the reaction centre of PS-II and that of other antenna carotenoid pigments is regulated by the portion of the xanthophyll violaxanthin, which is under control of the xanthophyll cycle.

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)-1,1- dimethylurea

1978 ◽  
Vol 33 (5-6) ◽  
pp. 413-420 ◽  
Author(s):  
J. J. S. van Rensen ◽  
D. Wong ◽  
Govindjee
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Chlorophyll A ◽  
Oxygen Evolution ◽  
Chlorophyll A Fluorescence ◽  
Chlorophyll Concentration ◽  
Fluorescence Emission ◽  
Photosynthetic Electron Transport ◽  
Percent Inhibition ◽  
Mechanism Of Inhibition

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: 1.The percent inhibition of oxygen evolution by a given herbicide concentration is the same at various light intensities except at very low intensities where the percent inhibition becomes larger. The same results are obtained with the herbicide DCMU. 2.The concentration of DCMU causing 50% inhibition of oxygen evolution decreases with de­creasing chloroplast (and thus of chlorophyll) concentration. With DNOC, the relative decrease is much less than with DCMU. At the inhibited molecule, there appears to be a cooperative binding of DCMU with two binding sites and a noncooperative binding of DNOC with only one binding site. 3.The chlorophyll a fluorescence induction is influenced by DNOC in the same characteristic way as it is by DCMU: both herbicides cause a faster rise in fluorescence yield than in control chloroplasts, although a higher concentration of the former is required for the same effect. 4.The chlorophyll fluorescence emission spectra at 77 CK show a slight decrease in the bands at 685 and 735 nm, and no or only a very slight decrease at 695 nm upon addition of high con­centrations of either DCMU or DNOC before the onset of illumination. 5.The degree of polarization of chlorophyll a fluorescence is lower after addition of DCMU or DNOC upon excitation by 460 or 660 nm light. It is concluded that, although the chemical structure of DNOC is completely different from that of DCMU, its site and mechanism of inhibition is similar to that of DCMU. Both herbicides inhibit electron transport between the primary electron acceptor of photosystem II and the plastoquinone pool. This causes a closing of the reaction centers of photosystem II. However, the interaction with the inhibited molecule is different for the two herbicides.

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