Photosystem II activity and triazine resistance in weeds

1987 ◽  
Vol 65 (10) ◽  
pp. 2147-2151 ◽  
Author(s):  
John Sinclair ◽  
Philip Macdonald
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Dark Period ◽  
Light Flash ◽  
Oxygen Electrode ◽  
Amaranthus Retroflexus ◽  
Herbicide Resistant ◽  
Oxygen Flash ◽  
Inactive Photosystem Ii ◽  
Oxygen Evolving

The oxygen-evolving properties of broken chloroplasts isolated from biotypes of Chemopodium album and Amaranthus retroflexus that were either sensitive or resistant to s-triazine herbicides were compared. The pattern of oxygen flash yields produced by herbicide-sensitive, dark-adapted chloroplasts of either species was reminiscent of that found with spinach chloroplasts. In contrast, dark-adapted chloroplasts isolated from the herbicide-resistant biotypes exhibited a highly damped oxygen flash pattern in which there was significant oxygen released after the first light flash. Analysis of these results with the Kok model of photosystem II (Kok, B., Forbush, B., and McGloin, M. 1970. Photochem. Photobiol. 11: 457–475) suggested that the unusual properties of the resistant organelles were due to the survival of significant amounts of S3 and S2 states during dark adaptation and to a higher proportion of inactive photosystem II reaction centres during each light flash. Deactivation experiments verified the suggestion that the S3 and S2 states more readily survive a 10-min dark period in resistant organelles. Information about electron transport on the oxidizing side of photosystem II was obtained with a modulated oxygen electrode and suggested that there was no difference between the two biotypes in the value of the rate constant of the reaction that limits the rate of electron transport between the water-splitting step and photosystem II.

A Diterpene γ-Lactone Derivative from Pterodon polygalaeflorus Benth. as a Photosystem II Inhibitor and Uncoupler of Photosynthesis

2006 ◽  
Vol 61 (3-4) ◽  
pp. 227-233 ◽  
Author(s):  
Beatriz King-Díaz ◽  
Flávio J. L. dos Santos ◽  
Mayura M. M. Rubinger ◽  
Dorila Piló -Veloso ◽  
Blas Lotina-Hennsen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Transport Rate ◽  
Atp Synthesis ◽  
Transport Rate ◽  
Hill Reaction ◽  
Oxygen Evolving Complex ◽  
Photosynthesis Inhibition ◽  
Chlorophyll A Fluorescence Transient ◽  
Oxygen Evolving

6α,7β-Dihydroxyvouacapan-17β-oic acid (1) was isolated from Pterodon polygalaeflorus Benth. Modification of 1 yielded 6α-hydroxyvouacapan-7β,17β-lactone (2) and then 6-oxovouacapan- 7β,17β-lactone (3). Photosynthesis inhibition by 3 was evaluated in spinach chloroplasts. The uncoupled non-cyclic electron transport rate and ATP synthesis were inhibited by 3, which behaved as a Hill reaction inhibitor. Furthermore, 3 acted as an uncoupler because it enhanced the basal and phosphorylating electron transport rate on thylakoids. This last property of 3 was corroborated when it was observed that it enhances the Mg2+-ATPase activity. In contrast, 3 did not affect photosystem I (PSI) activity. Analysis of the partial photosystem II (PSII) reactions from water to DCPIPox and water to silicomolybdate allowed to locate the inhibition sites at the redox components of PSII. The OJIP test of the chlorophyll a fluorescence transient confirmed that the inhibition sites were 1.) the oxygen-evolving complex (OEC) and 2.) by the formation of silent centers in the non-QA reducing centers.

Oxygen-Evolving System of Inactive Photosystem II Complexes in Chlorella

2004 ◽  
Vol 51 (5) ◽  
pp. 584-589
Author(s):  
Yu. K. Chemeris ◽  
N. S. Korolkov ◽  
N. Kh. Seifullina ◽  
A. B. Rubin
Keyword(s):  
Photosystem Ii ◽  
Evolving System ◽  
Oxygen Evolving System ◽  
Inactive Photosystem Ii ◽  
Oxygen Evolving

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.

The Effect of Antibodies to Neoxanthin on Electron Transport on the Oxygen Evolving Side of Photosystem II and the Reactions of this Antiserum with Various Chloroplast Preparations

1975 ◽  
Vol 30 (9-10) ◽  
pp. 622-627 ◽  
Author(s):  
Alfons Radunz ◽  
Georg H. Schmid
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Donor ◽  
Outer Surface ◽  
Thylakoid Membrane ◽  
Antirrhinum Majus ◽  
Donor Side ◽  
Oxygen Evolving ◽  
Electron Donation ◽  
Donor System

Antibodies to neoxanthin agglutinate stroma-free swellable chloroplasts from tobacco (Nico-tiana tabacum var. John William’s Broadleaf) and Antirrhinum (Antirrhinum majus) whereas stroma-freed chloroplasts, which have lost the swellability are not agglutinated despite the fact that antibodies to neoxanthin are specifically adsorbed. In this latter case the agglutination is hindered for sterical reasons. From this it is concluded that neoxanthin is located in the outer surface of the thylakoid membrane. The antiserum to neoxanthin inhibits the ferricyanide photo­ reduction in chloroplasts when water is the electron donor by 15%. With diphenylcarbazide in tris-treated chloroplasts no inhibition is observed. Hence, just as in the case of the antiserum to lutein the site of inhibition is on the donor side of potosystem II namely between water and the site of electron donation of diphenylcarbazide. Benzidine/ascorbate is another artificial electron donor system of photosystem II reported in the literature. The photoreduction of anthraquinone-2-sulphonate with this donor system is inhibited. In contrast to the antiserum to lutein the antiserum to neoxanthin inhibits DCMU-sensitive photophosphorylation reactions in the system H2O → ferricyanide and benzidine/ascorbate → anthraquinone-2-sulphonate. Therefore, the electron transport coupled to photophosphorylation is inhibited by the antiserum.

Effect of an Antiserum to a Thylakoid Membrane Polypeptide on the Primary Photoreaction of Photosystem II

1976 ◽  
Vol 31 (9-10) ◽  
pp. 594-600 ◽  
Author(s):  
Georg H. Schmid ◽  
Gernot Renger ◽  
Michael Gläser ◽  
Friederike Koenig ◽  
Alfons Radunz ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Electron Flow ◽  
Primary Electron ◽  
Hill Reaction ◽  
Ps Ii ◽  
Absorption Change ◽  
Oxygen Evolving ◽  
The Hill

Abstract As was described previously, an antiserum to polypeptide 11000 inhibited photosynthetic elec­tron transport on the oxygen evolving side of photosystem II. The effect of the antiserum on chloro­plasts from two tobacco mutants also clearly showed that the inhibition site is on the photosystem II-side of the electron transport chain. One of the two tobacco mutants lades the oxygen evolving capacity but exhibits some electron transport with tetramethyl benzidine, an artificial donor to PS II. In this mutant electron transport was barely inhibited. The effect of the antiserum on the primary photoevents showed that the initial amplitude of the absorption change of chlorophyll an at 690 nm and that of the primary electron acceptor X320 at 334 nm both diminished in the presence of the antiserum. Both signals were restored upon addition of diphenylcarbazide another artificial donor to photosystem II. Comparison of the degree of inhibition on the amplitudes of the fast and slow components of the 690 nm absorption change with the manometrically measured inhibition of electron transport shows that besides a full inactivation of a part of the reaction centers of photosystem II another part apparently mediates a fast cyclic electron flow around photosystem II as reported by Renger and Wolff earlier for tris-treated chloroplasts. Moreover, the antiserum affects the low temperature fluorescence in a way which is opposite to Murata’s effect of the Mg2+ -ion induced inhibition of energy spill-over from photosystem II to photosystem I. The antiserum under the condition in which the Hill reaction is inhibited lowered the 686 nm emission and enhanced the 732 nm emission which indicates an enhanced energy spill-over to photosystem I.

Characterization of photosystem II with the atomic-force microscope

1992 ◽  
Vol 50 (2) ◽  
pp. 1146-1147
Author(s):  
Kathleen M. Marr ◽  
Mary K. Lyon
Keyword(s):  
Photosystem Ii ◽  
Atomic Force Microscope ◽  
Three Dimensional ◽  
Biologically Active ◽  
Atomic Force ◽  
Freeze Etching ◽  
Image Averaging ◽  
Oxygen Evolving ◽  
Averaging Techniques

Photosystem II (PSII) is different from all other reaction centers in that it splits water to evolve oxygen and hydrogen ions. This unique ability to evolve oxygen is partly due to three oxygen evolving polypeptides (OEPs) associated with the PSII complex. Freeze etching on grana derived insideout membranes revealed that the OEPs contribute to the observed tetrameric nature of the PSIl particle; when the OEPs are removed, a distinct dimer emerges. Thus, the surface of the PSII complex changes dramatically upon removal of these polypeptides. The atomic force microscope (AFM) is ideal for examining surface topography. The instrument provides a topographical view of individual PSII complexes, giving relatively high resolution three-dimensional information without image averaging techniques. In addition, the use of a fluid cell allows a biologically active sample to be maintained under fully hydrated and physiologically buffered conditions. The OEPs associated with PSII may be sequentially removed, thereby changing the surface of the complex by one polypeptide at a time.

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