| | 1 | Author
| A. Trebst, E. Harth | Requires cookie* | | | Title
| Herbicidal N-Alkylated-Ureas and Ringclosed N-Acylamides as Inhibitors of Photosystem II  | | | | Abstract
| The inhibitory action of some herbicides on photosynthetic electron flow at photosystem I I in isolated chloroplasts was investigated. Emphasis in the study is on compounds, whose chemical structure seemed to be in disaccordance with the basic structural element, proposed to be required for a photosystem II inhibitor. The effective inhibition of photosynthetic oxygen evolution by N-alkylated urea-, pyrrolidone-and by substituted pyridazine-derivatives without a free NH-group is reported. A revised basic chemical structural element responsible for inhibition is deduced in order to include lactames (ringclosed N-acylamides) with and without hetero atoms. From this new groups of potential inhibitors, like triazolone-, thiadiazolone-and oxadiazolone-derivatives may be conceived. | | | |
Reference
| (Z. Naturforsch. 29c, 232 [1974]; received February 4 1974) | | | |
Published
| 1974 | | | |
Keywords
| Inhibitor, Herbicides, Photosynthesis, Photosystem II, Chloroplasts | | | |
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| default:Reihe_C/29/ZNC-1974-29c-0232.pdf | | | | Identifier
| ZNC-1974-29c-0232 | | | | Volume
| 29 | |
| 3 | Author
| M. Gläser, Ch Wolfff, G. Renger | Requires cookie* | | | Title
| Indirect Evidence for a Very Fast Recovery Kinetics of Chlorophyll-an in Spinach Chloroplasts | | | | Abstract
| The 690 nm absorption change reflecting the turnover of the system-II-reaction center chloro phyll, Chl-an (often referred to as P 680), has been investigated under different experimental con ditions in spinach chloroplasts. A comparison was made with oxygen evolution and with absorption changes of Chl-ai measured at 703 nm, both indicating the number of electrons produced by system II. It was found: 1. The dependency on actinic flash intensity of the initial amplitudes of the measured 690 nm ab sorption change, A A 0 (Chl-an), markedly differs for normal and for Tris-washed chloroplasts, respectively. 2. The saturation curve of A A 0 (Chl-an) in Tris-washed chloroplasts is similar to that for the total amplitude of the 703 nm absorption change, A A 0 (Chl-ai), in normal chloroplasts, and can be described by an exponential function. On the other hand, A A 0 (Chl-an) in normal chloro plasts exhibits a more complex biphasic dependency and much higher flash intensities are re quired for saturation. 3. Under repetitive flash group excitation and in the presence of an A D R Y (= acceleration of the deactivation reactions of the water-splitting enzyme system Y)-reagent the initial amplitude of the 690 nm absorption change oscillates in the same characteristic pattern as the oxygen evolu tion. 4. The initial amplitude of the 690 nm absorption change, A A 0(Chl-an)» in Tris-washed chloro plasts becomes significantly smaller (more than 50%) by the addition of system-II-electron donors (benzidine, p-phenylendiamine, tetraphenylboron), whereas the total amplitude of the 703 nm absorption change, Zly40(Chl-ai) increases 3 —4-fold. In order to explain these results, the existance of a very fast reduction kinetics of Chl-an+ is postulated, which is not detectable by our measuring equipment. The half time of this reaction is < 1 /us. Reaction centers with the very fast "undetected" Chl-an+-reduction are photochemically transformed into slower one by double hit processes with a comparatively low quantum yield. Furthermore, it is inferred, that the dark recovery kinetics of Chl-an is dependent on the charge accumulation state of the watersplitting enzyme system Y. This phenomenon is shown to explain also the oscillation pattern of delayed fluorescence. On the basis of the present results two alter native reaction schemes for the functional organization of the electron transport on the donor side of system II are discussed. | | | |
Reference
| (Z. Naturforsch. 31c, 712 [1976]; received August 13 1976) | | | |
Published
| 1976 | | | |
Keywords
| Photosynthesis, Photosystem II, Primary Reactions, Chlorophyll-an | | | |
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| default:Reihe_C/31/ZNC-1976-31c-0712.pdf | | | | Identifier
| ZNC-1976-31c-0712 | | | | Volume
| 31 | |
| 4 | Author
| JaneM. Bowes, AntonyR. Crofts | Requires cookie* | | | Title
| Interactions of Protons with Transitions of the Watersplitting Enzyme of Photosystem II as Measured by Delayed Fluorescence | | | | Abstract
| By measuring ms delayed fluorescence emission, we have investigated the interaction of protons in the reactions of the watersplitting enzyme of photosystem II. (1) In the presence of the electron transport mediators 2,3,5,6-tetramethyl-p-phenylene diamine (DAD) (in its reduced form) and methyl viologen and of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), the maximal intensity of the delayed fluorescence measured between 1 and 1.5m s after illumination was greater than the level reached in the presence of DCMU alone. (2) The stimulation of the delayed fluorescence was greater when the suspension was pre | | | |
Reference
| Z. Naturforsch. 33c, 271 (1978); received February 13 1978 | | | |
Published
| 1978 | | | |
Keywords
| Photosystem II, Watersplitting, Protons, Delayed Fluorescence | | | |
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| default:Reihe_C/33/ZNC-1978-33c-0271.pdf | | | | Identifier
| ZNC-1978-33c-0271 | | | | Volume
| 33 | |
| 5 | Author
| Govindjee, Paul Mathis, Claudie Vem Otte, Daniel Wong, Satham Saphon, ThomasW. Ydrzynskic, Jean-M Arie Briantais | Requires cookie* | | | Title
| Cation Effects on System II Reactions in Thylakoids: Measurements on Oxygen Evolution, the Electrochromic Change at 515 Nanometers, the Primary Acceptor and the Primary Donor | | | | Abstract
| Divalent cations are known to decrease the "spillover" of excitation energy from photosystem II (PS II) to PS I. At low light intensities, this does lead to an increased quantum yield of photo reactions in PS II. Contrary to some suggestions that PS II is activated at high light intensities, or in strong flashes of light by the addition of Mg2+, we suggest here that Mg2+ ions may not activate reaction center II, P 680. After brief light flashes, we do not find any significant enhancement in (a) 0 2 yield/flash, (b) proton yield/flash, (c) the amplitude of charge separation in PS II, as moni tored by 515 nm absorbance change, and (d) the amplitude of the reduced primary acceptor, as monitored by 320 nm absorbance change. Data on absorbance change at 820 nm suggest that the absence of Mg2+ does not lead to inactivation of electron donation to P 680+. | | | |
Reference
| Z. Naturforsch. 34c, 826—830 (1979); received July 9 1979 | | | |
Published
| 1979 | | | |
Keywords
| Photosynthesis, Flash Yields, Cation Effects, Photosystem II, Thylakoids | | | |
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| default:Reihe_C/34/ZNC-1979-34c-0826.pdf | | | | Identifier
| ZNC-1979-34c-0826 | | | | Volume
| 34 | |
| 6 | Author
| Wilhelm Menke, GeorgH. Schmid | Requires cookie* | | | Title
| Fluorescence and Photochemical Properties of Plants with Defective Photosystem II | | | | Abstract
| The mykotrophic orchid Neottia nidus-avis does not evolve oxygen in the light but is able to perform photophosphorylation. The low temperature fluorescence emission spectrum lacks the 680 and 690 nm bands. Hence, the spectroscopic chlorophyll a forms which are attributed to photosystem II do not occur in plastids of this orchid. The low temperature excitation spectrum of photosystem I fluorescence exhibits a maximum at 666 nm. The position o f this maximum ap pears not to be influenced by energy transfer and corresponds to the absorption maximum of the chlorophyll form which emits the photosystem I fluorescence. Energy migration, however, occurs from carotenoids whose absorption spectrum is shifted to longer wavelengths and which cause the yellow-brown color of the Neottia plastids. Room temperature fluorescence emission shows after the onset of light no variable part. Despite the fact that plastids of the tobacco mutant N C 95 at most evolve only traces o f oxygen the low temperature emission spectrum shows the three bands which are usually observed with fully functioning chloroplasts. However, the two bands at 680 and 690 nm are distinctly lower than with the wild type. The variable portion o f room temperature fluorescence is barely detectable. In line with the very low capacity for oxygen evolution, rates of electron transport partial reactions in the region of photosystem II are extremely low. In agreement with this observation no 690 nm absorption change signal is detected. However, a normal P7 + 00 signal is seen. In the presence of electron donors like reduced phenazine methosulfate the decay time o f the P7 ^0 signal is faster than with the wild type. The yellow tobacco mutant Su/su var. aurea which exhibits at high light intensities higher rates of photosynthesis than the wild type shows at low temperature an emission spectrum with stronger photosystem II bands than the wild type. | | | |
Reference
| Z. Naturforsch. 35c, 461 (1980); received March 14 1980 | | | |
Published
| 1980 | | | |
Keywords
| Photosystem II, Low Temperature Fluorescence, Tobacco, Neottia | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0461.pdf | | | | Identifier
| ZNC-1980-35c-0461 | | | | Volume
| 35 | |
| 8 | Author
| W. Im, F. J. Vermaas, G. Ern O, R. Enger, J. A. Arles, Rntzen | Requires cookie* | | | Title
| Herbicide/Quinone Binding Interactions in Photosystem II | | | | Abstract
| Many inhibitors prevent the oxidation o f the primary electron-accepting quinone (Q A) by the secondary quinone (Q B) in photosystem II by displacem ent o f Q B from its binding site. On the other hand, plastoquinone-1 and 6-azido-5-decyl-2,3-dim ethoxy-/?-benzoquinone displace herbicides. Binding studies show the herbicide/quinone interaction to be (apparently) competitive. The herbicide binding is influenced differentially by various treatments. In this paper it is shown that the affinity of, for example, brom oxynil is decreased by thylakoid unstacking or by light-or reductant-induced reduction o f certain thylakoid com ponents, whereas atrazine affinity remains unchanged. Furthermore, absence o f H C O j in the presence o f form ate leads to an affinity decrease o f bromoxynil and atrazine, but to an increase in i-dinoseb affinity. Other differential photosystem II herbicide effects are known from the literature. Since different and unrelated groups o f Q A oxidation inhibitors have been found, and because o f the above-mentioned dissim ilarities in binding characteristics for different inhibitor groups, the hypothesis o f non-identical, but "overlapping" binding sites for different herbicide groups and the native quinone must be more extensively defined. In this m anuscript we evaluate both the competitive herbicide/quinone binding m odel, and a m odel in which binding o f one ligand alters the protein conformation resulting in a dram atic decrease in the binding affinity o f ligands from other chemical groups; in this model ligands from the sam e or related chem ical groups bind competitively. Thus, the latter model proposes that only one herbicide or quinone m olecule can be bound with high affinity to the herbicide/quinone binding environm ent, but it depends on the chemical structure o f the ligands whether the binding interaction betw een two ligands is truly competitive or more indirect (allosteric), m ediated through the protein conform ation. | | | |
Reference
| Z. Naturforsch. 39c, 368 (1984); received D ecem ber 1 1983 | | | |
Published
| 1984 | | | |
Keywords
| Herbicide, Photosystem II, Plastoquinone, Photosynthesis, A llosteric interaction | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0368.pdf | | | | Identifier
| ZNC-1984-39c-0368 | | | | Volume
| 39 | |
| 9 | Author
| D. Anny, J. Blubaugh, G. Ovindjee | Requires cookie* | | | Title
| Comparison of Bicarbonate Effects on the Variable Chlorophyll a Fluorescence of C 0 2-Depleted and Non-C02-Depleted Thylakoids in the Presence of Diuron | | | | Abstract
| Evidence is presented from chlorophyll a fluorescence transient data for two sites o f bicar bonate (H C O j*) action in photosystem II. Both the absence o f H C O j (H C O j-depleted thyla koids) and a high concentration o f H C O j (60 m M H C O j added to non-depleted thylakoids) accelerate the variable chlorophyll a fluorescence rise in the presence o f 10 |i m diuron (D C M U). In non-HCOj-depleted thylakoids the effect is independent o f the order in which H C O j and DCM U are added, whereas in H CO J-depleted thylakoids, the effect is seen only when H C O j is added before DCM U. We propose that the effect seen in H C O j-depleted thylakoids is indirectly due to the binding o f H C O j functionally near the site o f D C M U binding, which is also where H CO j exerts its major effect on electron transport between the primary quinone QA and the plasto-quinone pool. We suggest that the smaller effect seen in non-HCOj-depleted thylakoids is due to the binding of HCOj at a second, lower affinity site. Binding at this site appears to require light, in con trast to the higher affinity site, which is inhibited by light. Bathocuproine, an inhibitor o f the H20 -to-silicomolybdate partial reaction, is synergistic with H C O j in its effect on the variable chlorophyll a fluorescence o f non-H C O j-depleted thylakoids, and may bind heterotropically with H CO j. Thus, this second site o f H C O j binding appears to be functionally near the batho cuproine binding site. | | | |
Reference
| Z. Naturforsch. 39c, 378 (1984); received N ovem ber 14 1983 | | | |
Published
| 1984 | | | |
Keywords
| Bicarbonate Effect, Chlorophyll Fluorescence, Photosystem II, Diuron, Bathocuproine | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0378.pdf | | | | Identifier
| ZNC-1984-39c-0378 | | | | Volume
| 39 | |
| 10 | Author
| HowardH R Obinson, JulianJ E Aton-R, Ye, JackJ S Van, R. Ensen, G. Ovindjee | Requires cookie* | | | Title
| The Effects of Bicarbonate Depletion and Formate Incubation on the Kinetics of Oxidation-Reduction Reactions of the Photosystem II Quinone Acceptor Complex | | | | Abstract
| Chloroplast thylakoid membranes depleted o f bicarbonate exhibit a slowed oxidation o f the primary quinone acceptor (QA) by the secondary quinone acceptor (Q B) o f photosystem II. The kinetics o f these slowed reactions have been follow ed by using short xenon flashes o f light both to excite photosystem II and to probe the redox state o f Q A. Thylakoids incubated with formate but not depleted o f bicarbonate showed the sam e pattern o f slowed reaction kinetics o f the quinone acceptors as seen in bicarbonate-depleted thylakoids. This led us to conclude that there was a simple com petition between bicarbonate and formate at this site; however, steady-state electron transfer measured with an oxygen electrode showed that although the bicarbonate-depleted thylakoids were indeed inhibited, rates in the form ate-incubated thylakoids were only slightly slowed. We suggest that the inhibition seen at the quinone acceptor site o f photosystem II depends in a subtle way upon the rate o f exchange o f bicarbonate and formate at this site. | | | |
Reference
| Z. Naturforsch. 39c, 382 (1984); received N ovem ber 14 1983 | | | |
Published
| 1984 | | | |
Keywords
| Chloroplasts, Photosystem II, Bicarbonate, Formate, Plastoquinone | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0382.pdf | | | | Identifier
| ZNC-1984-39c-0382 | | | | Volume
| 39 | |
| 11 | Author
| A. Trebst, W. D. Onner, W. D. Raber | Requires cookie* | | | Title
| Structure Activity Correlation of Herbicides Affecting Plastoquinone Reduction by Photosystem II: Electron Density Distribution in Inhibitors and Plastoquinone Species | | | | Abstract
| Molecular orbital calculations o f the net charge and the n charge distribution in several inhibitors and herbicides o f the functionally related group o f the diuron and dinoseb type are reported. They confirm the m odel that urea, am inotriazinone and triazine herbicides all have in common a positive ^-charge at a particular atom considered to be essential for binding. Phenol type inhibitors have different charge distribution and a m odel for their essential features is presented. The calculations support the finding that two different subunits with different binding characteristics are involved in inhibitor and plastoquinone function on the acceptor side o f photosystem II. Force-field model building and MO calculations o f the charge distribution o f a plastoquinone analogue with a butenyl side chain, o f two o f its sem iquinone forms and o f the hydroquinone, are reported, as well as their conform ation with the lowest energy content and their likely anionic forms. | | | |
Reference
| Z. Naturforsch. 39c, 405—411 (1984); received D ecem ber 23 1983 | | | |
Published
| 1984 | | | |
Keywords
| Herbicides, Plastoquinone, MO Calculation, Photosystem II | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0405.pdf | | | | Identifier
| ZNC-1984-39c-0405 | | | | Volume
| 39 | |
| 12 | Author
| E. K. Pistorius, G. H. Schmid | Requires cookie* | | | Title
| Studies on the O2 Evolution under Flash Light Illumination in Preparations of A nacystis nidulans | | | | Abstract
| The 0 2 yield under flash light illum ination in preparations o f Anacystis nidulans was exam ined in the presence o f redox components such as ferricyanide and ferrocyanide. W hen ferricyanide (1 mM) was added to the lyophilized, lysozym e treated and ED TA w ashed cells o f A. nidulans the familiar Joliot-Kok oscillalion with m axim um on the third flash and periodicity o f four was observed (in the presence o f added CaCl2 and M nCl2). H owever, when the ferricyanide con centration was increased to about 8 m M , a reduction o f the 0 2 evolution under flash illum ination was observed, and an 0 2 uptake could clearly be seen under the First and second flash. This 0 2 uptake was inhibited by D C M U and o-phenanthroline, but was not influenced by KCN or salicylhydroxamic acid. As ferrocyanide was progressively added to 1 m M ferricyanide, the oscillations faded out and the steady-state 0 2 evolution decreased. Light would progressively increase the 0 2 evolution and reduce the dam ping o f the oscillations. Two patterns o f 0 2 evolution under short saturating light flashes were observed with these Anacystis preparations on first illum ination in the presence o f cations but in the absence o f ferri cyanide. One pattern corresponded to the typical pattern w hich has been repeatedly described in the literature, but the second pattern gave the indication o f an initial "over-reduced" state o f the photosystem II reaction center. W ith suitable procedures the two patterns were interchangeable. Moreover, the effect o f L-arginine on the flash pattern was exam ined. The results are discussed in connection with the possible dual function o f the previously described flavin protein as an L-amino acid oxidase and as a com ponent o f the 0 2 evolving reaction center (E. K. Pistorius and H. Voss, Eur. J. Biochemistry 1 2 6 ,2 0 3 -2 0 9 (1982)). | | | |
Reference
| Z. Naturforsch. 39c, 1097—1103 (1984); received August 20 1984 | | | |
Published
| 1984 | | | |
Keywords
| 0 2 Evolution, Photosystem II, Cyanobacteria, A nacystis nidulans | | | |
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| default:Reihe_C/39/ZNC-1984-39c-1097.pdf | | | | Identifier
| ZNC-1984-39c-1097 | | | | Volume
| 39 | |
| 14 | Author
| Jack Farineau | Requires cookie* | | | Title
| In Pea Thylakoids, a Special Thermoluminescence Band Was Observed at Low Temperature after Photoinhibitory Treatments Performed under Aerobic Conditions, either in vivo (in Leaf) or in vitro | | | | Abstract
| Characteristics o f thermoluminescence (TL) glow curves were studied in thylakoids isolated from pea leaves after an exposure to very high light in the TL device. The inhibition o f p h oto synthesis was detected both as decreases o f oxygen evolution rates and o f variable fluores cence. In another more classical experiment, leaves were exposed to high light at low tempera ture (5 °C) for 4 h and recovery o f normal PS II characteristics were followed during a 20 h time period under low light at 20 °C. TL study was performed on thylakoids isolated from these leaves. Charging o f bands was performed by an illumination at low temperature (-8 0 °C). Illumination at low temperature (-8 0 °C) induces 2 types o f TL bands called Z variable (Zv) band peaking at about —70 °C and a classical B band peaking at 35 °C. B band is ascribed to recombination in pairs S2/3QB", whereas the origin o f Zv bands remains unclear. M odified Zv bands, with flat shape and presenting a large part resistant to ethanol, were evidenced after som e minutes o f dark adaptation, both in light-exposed thylakoids and in thylakoids isolated from photoinhibited leaves. This ethanol resistant part in Zv band was only induced by p h oto inhibitory treatment performed under aerobic conditions (2 1 % 0 2 in media), both in vitro and in vivo; thus, the appearance o f the special Zv band would be related to an oxidative process accompanying photoinhibition. B bands presented reduced sizes and a shift o f peak maximum o f about 5 °C after some minutes o f dark adaptation. In vivo, the recovery o f a high PS II activ ity and o f B bands displaying normal characteristics occurs parallely to reappearance o f Zv bands with normal shape and with a vestigial ethanol resistant band. | | | |
Reference
| Z. Naturforsch. 47c, 875—8 (1992); received July 27/A ugust 27 1992 | | | |
Published
| 1992 | | | |
Keywords
| Pea, Photoinhibition, Photosystem II, Thermoluminescence, Thylakoid, Zv Band | | | |
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| default:Reihe_C/47/ZNC-1992-47c-0875.pdf | | | | Identifier
| ZNC-1992-47c-0875 | | | | Volume
| 47 | |
| 15 | Author
| Ichiro Honda, Makoto Sibagaki, Koichi Yoneyama, Yoshihiro Nakajima, Makoto Konnai, Nobutaka Takahashi, Shigeo Yoshida | Requires cookie* | | | Title
| Photosystem II Inhibition by Phloroglucinol Derivatives Having Both Phenol and Urea Functionalities | | | | Abstract
| Esters o f 3-nitrophloroglucinecarboxylic acid were found to be active photosystem II (PS II) inhibitors, as were the amides, indicating that, in their structures, the substituted phlorogluci nol nuclei themselves plays a major roles in PS II inhibition. A m ong the phenylureidoalkyl esters tested, 3,4-dichlorophenylurea com pound having two amino hydrogen atom s showed high activities. Optimal activity was associated with compounds in which the oxygen atom and the urea structure in the ester side chain were connected via an ethylene group. | | | |
Reference
| Z. Naturforsch. 48c, 159 (1993); received November 3 1992 | | | |
Published
| 1993 | | | |
Keywords
| Photosystem II, Electron Transport Inhibition, Phloroglucinol Derivatives | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0159.pdf | | | | Identifier
| ZNC-1993-48c-0159 | | | | Volume
| 48 | |
| 16 | Author
| Koichi Yoneyama, Yoshihiro Nakajima, Masaru Ogasawara, Hitoshi Kuramochi, Makoto Konnai, Hajime Iwamura, Fumihiko Sato, Katsunori Ichinose, Tadao Asami, Nobutaka Takahashi, Shigeo Yoshida | Requires cookie* | | | Title
| Photosystem II Inhibition by Pyran-enamine Derivatives | | | | Abstract
| Through the studies on structure-activity relationships o f 5-acyl-3-(l-am inoalkylidene)-4-hydroxy-2 H-pyran-2,6(3 H)-dione derivatives in photosystem II (PS II) inhibition, overall lipophilicity o f the m olecule was found to be a major determinant for the activity. In the sub stituted N -benzyl derivatives, not only the lipophilicity but also the electronic and steric char acters o f the substituents greatly affected the activity. Their mode o f PS II inhibition seemed to be similar to that o f D C M U , whereas pyran-enamine derivatives needed to be highly lipophilic to block the electron transport in thylakoid membranes, which in turn diminished the permea bility through biomembranes. | | | |
Reference
| Z. Naturforsch. 48c, 163 (1993); received November 3 1992 | | | |
Published
| 1993 | | | |
Keywords
| Photosystem II, Electron Transport Inhibition, Pyran-enamine Derivatives | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0163.pdf | | | | Identifier
| ZNC-1993-48c-0163 | | | | Volume
| 48 | |
| 17 | Author
| H. Adar Kless3, Michal Oren-Shamirb, ItzhakO. Hadc, M. Arvin Edelm, Wim Vermaasa | Requires cookie* | | | Title
| Protein Modifications in the D 2 Protein of Photosystem II Affect Properties of the Q B/Herbicide-Binding Environment | | | | Abstract
| The D 2 protein contains an extended loop (the D-de loop) between helices D and de at the reducing side o f photosystem II (PS II). Characterization o f D 2 mutants o f the cyanobacte rium Synechocystis sp. PCC 6803 has indicated that the length and amino acid com position o f the D-de loop are not critical for basic PS II functions, although most o f the residues in that region are conserved phylogenetically. Here we show using herbicide binding and electron-flow inhibition measurements that drastic modifications in the D-de loop o f the D 2 protein modify the interaction o f some PS II-directed herbicides with their binding niche. The stability o f (semi-)reduced Q B in its binding pocket is altered in at least two o f the mutants, as indicated by a shifted peak temperature o f the thermoluminescence signal originating from charge recombi nation involving QB. These results suggest a close functional association between the D-de loop o f the D 2 protein and the Q B/herbicide-binding environment, which is viewed as being coordinated mostly by re sidues o f the D 1 protein. This represents one o f the first examples o f m odification o f the Q B/ herbicide-binding domain by mutations in the D 2 protein. | | | |
Reference
| Z. Naturforsch. 48c, 185—190 (1993); received November 23 1992 | | | |
Published
| 1993 | | | |
Keywords
| Herbicides, Plastoquinone, Photosystem II, Thermoluminescence, Cyanobacteria | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0185.pdf | | | | Identifier
| ZNC-1993-48c-0185 | | | | Volume
| 48 | |
| 18 | Author
| V. Ictor, B. Curw, G. Ert, S. Chan Sk Er, O. Scar, J. De, V. Os, J. S. Van Rensen | Requires cookie* | | | Title
| Comparison of Photosynthetic Activities in Triazine-Resistant and Susceptible Biotypes of Chenopodium album | | | | Abstract
| Triazine-resistant and susceptible Chenopodium album plants were grown at low and at high light irradiances. A t the lower light irradiance the dry m atter production of the resistant and the susceptible plants were almost similar. At the higher irradiance the resistant biotype had a significantly lower production. Fluorescence studies showed that the photochemical yield and the photosystem II electron transport rate were lower in the resistant biotype. It could be demonstrated in intact leaves that the lower productivity of the resistant biotype is caused by a higher sensitivity to photoinhibition. However, when studying effects of photoinhibition on electron flow and photophosphorylation in isolated thylakoids o f the two biotypes, no signifi cant differences between resistant and susceptible plant materials were observed. It is suggest ed that the difference between resistant and susceptible biotypes connected with processes pro tective against photoinhibition in intact leaves, are lost during the isolation of thylakoids. | | | |
Reference
| Z. Naturforsch. 48c, 278 (1993); received November 26 1992 | | | |
Published
| 1993 | | | |
Keywords
| Chloroplasts, Triazine-Resistance, Photosystem II, Photoinhibition, Fluorescence | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0278.pdf | | | | Identifier
| ZNC-1993-48c-0278 | | | | Volume
| 48 | |
| 19 | Author
| U. Hegde, S. Padhye, L. Kovács, A. Vozár, S. Demeter | Requires cookie* | | | Title
| Modification of Histidine Residues of Photosystem II by Diethyl Pyrocarbonate Inhibits the Electron Transfer between the Primary (QA) and Secondary (QB) Quinone Acceptors | | | | Abstract
| The effect o f diethyl pyrocarbonate (D EPC) on the photosynthetic electron transport was investigated in isolated spinach thylakoids by partial electron transport rate and thermolumi nescence measurements. Incubation o f thylakoids at pH 6.5 with 5 mM DEPC for 15 min re sulted in a considerable inhibition o f electron transport from water to dichlorophenolindo-phenol. The inhibition was only partially releaved by addition o f the donor, diphenylcarbazide indicating the effect o f DEPC both on the donor and acceptor sides o f PS II. In the thermolu minescence glow curve DEPC-treatm ent abolished the B band (S2Q B~ radiative charge recom bination) at 30 °C with a concom itant appearance o f the Q band (S2QA~ charge recombina tion) at 10 °C. This suggests that in isolated thylakoids possessing an active water-splitting sys tem DEPC affects the electron transfer from QA to QB but does not inhibit the electron transport from manganese to QA during the S t—>S2 transition o f the water-splitting system. At the acceptor side o f PS II the targets o f DEPC are probably the histidines which are coordinat ed to the non-hem e iron. Illumination o f thylakoids at -8 0 °C following DEPC addition after two preflashes at 5 °C resulted in the replacement o f the A (A T) thermoluminescence band at -3 0 °C with a band appearing at -1 5 °C. This observation can be explained by the effect o f DEPC on a donor side histidine com ponent participating in the generation o f the A (A T) band. Consequently, in the interpretation o f results obtained by DEPC treatment o f PS II, both the donor and acceptor side effects o f DEPC should be considered. | | | |
Reference
| Z. Naturforsch. 48c, 896—9 (1993); received May 4/September 6 1993 | | | |
Published
| 1993 | | | |
Keywords
| Diethyl Pyrocarbonate, Histidine, Photosynthesis, Photosystem II, Thermoluminescence | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0896.pdf | | | | Identifier
| ZNC-1993-48c-0896 | | | | Volume
| 48 | |
| 20 | Author
| Jack Farineaua, DanielleM. Laval-, Artinb | Requires cookie* | | | Title
| Characteristics of Thermoluminescence Bands of Euglena Cells Belonging to 2 Lines Presenting Different Degrees of Diuron-Resistance | | | | Abstract
| We have analysed the thermoluminescence (TL) properties of two lines o f Euglena exhibit ing two degrees of resistance to diuron, by a factor of 100 (Z R 25) and 1000 (Z R 250) respectively, as compared to wild type line (Z). In addition, the two ZR lines developped an identical resistance to atrazine since the I50 for this herbicide in each line was 75 times larger than in wild type. Special TL characteristics were evidenced in the two lines. Bands after 2 flashes (or more) showed a shift o f the peak maximum towards low temperature, the shift being the largest in the most DCM U-resistant cells. Similar results were obtained with isolated thylakoids, except that the TL bands appeared at a temperature higher than in corresponding cells. Oscillations in the amplitude of the bands in a flash sequence were largely damped in cells (and thylakoids), particularly in the most DCM U-resistant lines. The results are interpreted as indicating accumulation of Q a "Qb after flashes due to a decrease of the equilibrium constant for the reaction Q a ~Qb ^ QaQb~ accompanying the D CM U resistance. | | | |
Reference
| Z. Naturforsch. 50c, 86—9 (1995); received October 12/November 21 1994 | | | |
Published
| 1995 | | | |
Keywords
| Diuron, Euglena, Herbicide-Resistance, Photosystem II, Thermoluminescence | | | |
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| default:Reihe_C/50/ZNC-1995-50c-0086.pdf | | | | Identifier
| ZNC-1995-50c-0086 | | | | Volume
| 50 | |
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