| | 21 | Author
| Krishna Bala, Swati Kolli, Prasanna Tiwari, Mohanty | Requires cookie* | | | Title
| Spirulina platensis  | | | | Abstract
| When Spirulina platensis filaments were exposed to 0.75 mW.m_2.s_1 of ultraviolet-B radi ation (the ultraviolet-B radiation under clear sky condition is —1.0 mW.m_2.s_1), an inhibi tion in photosystem II activity was observed, the inhibition being 90% after 90 min exposure. Upon exposure to ultraviolet-B, the room temperature emission characteristics of Spirulina cells were altered when excited with light primarily absorbed by chlorophyll a or phycobili-somes. When the cells were exposed for 3 h the emission at 685 nm (F685), when excited at 440 nm (primarily chlorophyll a absorption), was enhanced compared to 715 nm (F 715) band of photosystem I suggesting a decrease in energy transfer from photosystem II to photosys tem I. Similarly, when the cells were excited at 580 nm (primarily the phycobilisomes), the ratio of emission intensity at 685 nm (F 685) to that of 655 nm (F655) was decreased in the exposed cells. This change in emission characteristics seems to be linked with the uncoupling of the energy transfer from allophycocyanin to chlorophyll a of photosystem II. A small shift in emission peak positions was also indicated when excited either at 440 nm or 580 nm. Analysis of the fast induction of chlorophyll a transients in the presence and absence of 10 jam 3-(3,4-dichlorophenyl)-l,l-dimethylurea (D CM U) indicated that ultraviolet-B expo sure initially affects Q A, the primary stable acceptor of photosystem II, and then the plas-toquinone (PQ) pool. Our results on the loss in photosystem Il-catalyzed Hill activity with p-benzoquinone or dichlorobenzoquinone as electron acceptors also supports the contention that ultraviolet-B, even at low dose, initially alters the Q A of photosystem II and subsequently PQ pool. The analysis of functional pool size of Spirulina suggests a substantial decrease in the functional pool size after 2 h UV-B exposure. These results indicate that in Spirulina low intensity of ultraviolet-B initially damages the reaction centre of photosystem II. | | | |
Reference
| Z. Naturforsch. 53c, 369—3 (1998); received December 15 1997 | | | |
Published
| 1998 | | | |
Keywords
| Fluorescence Transients, Photosystem II, Quinones, Spirulina, Ultraviolet-B | | | |
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| default:Reihe_C/53/ZNC-1998-53c-0369.pdf | | | | Identifier
| ZNC-1998-53c-0369 | | | | Volume
| 53 | |
| 22 | Author
| Zoltán Takács, Zsolt Csintalan, Zoltán Tuba | Requires cookie* | | | Title
| Responses of the Lichen Cladonia convoluta to High C 0 2 Level and Heavy Metal Treatment | | | | Abstract
| Despite of the downward acclimation of photosynthesis in C. convoluta, increased net photosynthesis and carbon balance can be anticipated in response to elevated atmospheric C 0 2 level. C 0 2 exchange measurement seems to be m ore indicative when detecting heavy metal stress than fluorescence parameters. Among these, the relative fluorescence decrease ratio (R F d 690) shows damage first, suggesting that the primary attack site for heavy metal ions is C 0 2 fixation and reaction centres are harmed last. Long-term elevated C 0 2 amelio rates partly this damage by improving C-balance to a greater extent in the heavy-metal stressed lichens. | | | |
Reference
| Z. Naturforsch. 54c, 797—8 (1999); received November 15 1998/M arch 5 1999 | | | |
Published
| 1999 | | | |
Keywords
| Cadmium, Lead, Fluorescence, Respiration, Photosystem II | | | |
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| default:Reihe_C/54/ZNC-1999-54c-0797.pdf | | | | Identifier
| ZNC-1999-54c-0797 | | | | Volume
| 54 | |
| 23 | Author
| Éva Hideg, Sándor Demeter | Requires cookie* | | | Title
| Thermoluminescence and Delayed Luminescence Characterization of Photosystem II a and Photosystem II p Reaction Centers | | | | Abstract
| The thermoluminescence and delayed luminescence characteristics of PS II" and PS IIp centers were investigated in BBY particles and stroma thylakoids, respectively. The BBY particles exhib-ited a thermoluminescence band at 25 °C (B band) which was associated with the charge recombi-nation of the S 2 Qb" redox couple and underwent period-2 oscillation in a sequence of flashes. In the flash-induced decay of delayed luminescence of BBY particles a component with a half-time of 34 s corresponded to the B thermoluminescence band and was also assigned to S2OB charge recombination. No corresponding thermoluminescence or delayed luminescence components as-sociated with the secondary acceptor OB could be observed in the glow curve or delayed lumines-cence decay of stroma thylakoids. These observations indicate that unlike PS IIa the PS Hp centers are not associated with the two-electron gate, 0B. | | | |
Reference
| Z. Naturforsch. 43c, 596—600 (1988); received May 2 1988 | | | |
Published
| 1988 | | | |
Keywords
| Photosynthesis, Photosystem II, Thermoluminescence, Delayed Luminescence | | | |
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| default:Reihe_C/43/ZNC-1988-43c-0596.pdf | | | | Identifier
| ZNC-1988-43c-0596 | | | | Volume
| 43 | |
| 25 | Author
| Imre Vass, Narendranath Mohanty, Sándor Demeter | Requires cookie* | | | Title
| Photoinhibition of Electron Transport Activity of Photosystem II in Isolated Thylakoids Studied by Thermoluminescence and Delayed Luminescence | | | | Abstract
| The effect of photoinhibition on the primary (Oa) and secondary (Ob) quinone acceptors of photosystem II was investigated in isolated spinach thylakoids by the methods of thermolumines-cence 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 S;OA 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 S 2 0A and S 2 OB 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 thermo-luminescence 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 lumines-cence 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 Ob binding site in the reaction center of photosystem II or QA and OB undergo simultaneous damage. | | | |
Reference
| Z. Naturforsch. 43c, 871—876 (1988); received August 12 1988 | | | |
Published
| 1988 | | | |
Keywords
| Photosynthesis, Photoinhibition, Photosystem II, Thermoluminescence, Delayed Luminescence | | | |
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| default:Reihe_C/43/ZNC-1988-43c-0871.pdf | | | | Identifier
| ZNC-1988-43c-0871 | | | | Volume
| 43 | |
| 26 | Author
| John Bowyer1, Mark Hiltonb, Julian Whitelegge3, Philip Jewess6, Patrick Camillerib, Antony Croftsc, Howard Robinsonc | Requires cookie* | | | Title
| Molecular Modelling Studies on the Binding of Phenylurea Inhibitors to the D 1 Protein of Photosystem II | | | | Abstract
| A hypothetical molecular model of part of the D 1 protein of photosystem II, based on the analogous portion of the L subunit of the Rhodopseudomonas viridis reaction centre, has been used to study the binding of an extended hydrophobic phenylurea inhibitor (N,N-dimethyl-carbamoyl)4 -amino-4 '-chloro-rra«5 -stilbene) (I) to the Q B site. The inhibitor was fitted by eye into a cleft in the site, and a limited part of the inhibitor/D 1 complex was energy minimized. The gross orientation of the inhibitor placed the dimethylurea moiety towards the predicted binding domain of the plastoquinone head group, and the stilbene moiety directed along the quinone isoprenoid side chain binding domain, suggesting a similar pathway of approach of the two molecules from the membrane into the binding site. Binding interactions of the inhibi tor included hydrogen bonds to the side chain hydroxyl of ser 264 and the peptide carbonyl group of ala 251, with the side chain hydroxyl of ser 268 as an alternative ligand. Numerous hydrophobic contacts were also possible. Although phenylureas do not bind to reaction centres of Rp. viridis, many of the binding interactions to D 1 could also be detected in Rp. viridis. However, the ß-CH2 and 5-C02-groups of glu 212 in Rp. viridis are located in the corresponding region of D 1 occupied by the dimethylurea moiety of the inhibitor in our model of its binding to D 1. This may explain why diuron (D C M U) does not bind to Rp. viridis reac tion centres. | | | |
Reference
| Z. Naturforsch. 45c, 379—387 (1990); received November 23 1989 | | | |
Published
| 1990 | | | |
Keywords
| Phenylureas, Photosystem II, D 1 Protein, Molecular Modelling | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0379.pdf | | | | Identifier
| ZNC-1990-45c-0379 | | | | Volume
| 45 | |
| 27 | Author
| M. D. Arie-Jose, Elrieu | Requires cookie* | | | Title
| The Effects of 3-(3,4-Dichlorophenyl)-l,l-dimethylurea on the Photosynthetic Oxygen Complex | | | | Abstract
| In the presence o f trypsin and ferricyanide as external electron acceptor, lettuce chloroplasts are resistant to DCM U, showing that the inhibitory site o f D C M U is only situated on the accep tor side o f photosystem II. However, kinetic properties o f the oxygen evolving com plex are m od i fied at non-saturating concentrations o f D C M U . These changes are interpreted in terms o f a model with two distinct charges separation systems on the sam e center: the auxiliary donor-acceptor system D Q L implicated in the transitions S| -» • S 2 and S2 -*■ S 3 would be m uch less affected by DCM U than the main donor-acceptor system Y Q H after the first flash. | | | |
Reference
| Z. Naturforsch. 39c, 347—350 (1984); received N ovem ber 28 1983 | | | |
Published
| 1984 | | | |
Keywords
| Herbicides, Oxygen Evolution, Photosystem II, Electron Acceptors, Electron D onors | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0347.pdf | | | | Identifier
| ZNC-1984-39c-0347 | | | | Volume
| 39 | |
| 29 | Author
| Z. Naturforsch | Requires cookie* | | | Title
| Redox-State Dependent Changes of Inhibitor-Binding to the Photosystem II Acceptor Complex | | | | Abstract
| Binding o f radioactively labelled D C M U , ioxynil and terbutryn to spinach chloroplasts is determined following preillum ination by single-turnover, saturating light flashes. W ith all o f the three herbicides binary oscillations o f binding are observed. D ark-adapted sam ples, or those pre illuminated by an even number o f flashes, bind more inhibitor than sam ples preillum inated by an odd number o f flashes. Binding oscillations depend on inhibitor incubation tim e and on the seasonal adaptation o f the plants. The binding kinetics follow ing a single flash display three phases, the last two o f which can be correlated with reoxidation kinetics o f the secondary p h oto system II acceptor Qb, as determined by fluorescence measurem ents. Analysis o f the binding at DCM U concentrations up to 10"7 M free D C M U yields identical binding constants for dark-and flash preilluminated samples, but much less binding sites follow ing one flash. It is concluded that up to 10~7 M free DCM U, centers with bound Q b do not contribute significantly to total binding. Displacement o f Q b from the binding site is half-saturated at about 10-6 M D C M U , as m onitored via fluorescence induction. The data are considered strong support for the Velthuys 'inhibitor-Q i competition model'. | | | |
Reference
| Z. Naturforsch. 39c, 397 (1984); received D ecem ber 1 1983 | | | |
Published
| 1984 | | | |
Keywords
| Inhibitor Binding, Photosystem II, Binary O scillation, Chlorophyll Fluorescence | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0397.pdf | | | | Identifier
| ZNC-1984-39c-0397 | | | | Volume
| 39 | |
| 30 | Author
| K. Burda3-, K. Strzałkab, G. H. Schmid3 | Requires cookie* | | | Title
| Europium-and Dysprosium-Ions as Probes for the Study of Calcium Binding Sites in Photosystem II | | | | Abstract
| Trivalent lanthanide cations are suitable probes for C a2+-binding sites in photosystem II (PS II). PS II membranes prepared from Nicoticinci tabacum, intact and depleted of the extrinsic polypeptides were exposed to lanthanide ions (D y3+ and E u 3+). Small concen trations of dysprosium and europium ions enhance oxygen evolution under short saturating flashes. Higher concentrations of the rare earth cations cause the release of the three extrinsic peptides (17, 23 and 33 kDa) and reduce 0 2 yield. The reactivation of the PS II membranes, thus depleted of the 33 kDa subunit, by Ca2+ ions is not possible. Comparing E u 3+ with Dy3+ in this effect shows that E u 3+ is m ore effective than Dy3+, because a lower E u 3+-concentration in comparison to that of Dy3+ inactivates 0 2-evolution. The differences between europium and dysprosium can be explained by their different ionic radius. Our results suggest the existence of two Ca-binding regions: one with a low affinity for calcium would be located on the contact surface of the 23 and 33 kDa proteins and the second one with a high affinity, should be located close to the Mn-cluster and to tyrosine-161 (Z). The more tightly-bound calcium would be responsible for the activity of the PS II system. | | | |
Reference
| Z. Naturforsch. 50c, 220 (1995); received O ctober 6/O ctob er 31 1994 | | | |
Published
| 1995 | | | |
Keywords
| Calcium-Binding Sites, Photosystem II, Tobacco, Oxygen Evolution S-States | | | |
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| default:Reihe_C/50/ZNC-1995-50c-0220.pdf | | | | Identifier
| ZNC-1995-50c-0220 | | | | Volume
| 50 | |
| 31 | Author
| AchimE G Aua, HubertH. Tholeb, ElfriedeK. Pistoriusa | Requires cookie* | | | Title
| Isolation and Partial Characterization of a Manganese Requiring L-Arginine Metabolizing Enzyme Being Present in Photosystem II Complexes of Spinach and Tobacco | | | | Abstract
| A low L-arginine metabolizing enzyme (L -A M E) activity leading to ornithine, urea and additional products not identified so far could be detected in photosystem II (PS II) m em branes of spinach and of the chlorophyll deficient tobacco mutant Su/su. The detectable L-AM E activity was very low in untreated PS II membranes, but increased significantly (about 10 fold) when the extrinsic peptides (psbO, P and Q gene products) were removed -suggesting that the L-AM E is exposed at the lumen side o f PS II. It was possible to isolate the detergent-solubilized protein from CaCl2-washed PS II membranes of spinach by a com bination of anion and cation exchange columns. On the basis of SDS PAGE the protein was hom ogenous and had an apparent molecular mass of 7 kDa. N-terminal sequencing of the polypeptide gave a contiguous sequence of 20 amino acids showing no hom ologies to PS II polypeptides as yet sequenced. After chromatography o f the L-AM E on an anion exchange column at pH 9.5 (last purification step) a completely inactive enzyme was obtained. Maximal reactivation was achieved by dialyzing the protein against H epes-N aO H buffer in the pH range of 6.5 to 7.5 containing 100 m M chloride or sulfate (being the most effective anions). The L-AM E activity was totally dependent on manganese added to the reaction mixture. Moreover, there were indications of a second cation binding site being more sequestered and requiring bound Ca2+ or Mn2+ for activity (Sr2+ was less effective and Mg2+ was ineffective). There are indications that the protein contains a redox active group -possibly an amino-acid-derived quinonoid (based on a redox cycling assay with glycine and nitroblue tetrazo-lium). The capability of this PS II associated protein to bind the cofactors of water oxidation and having a redox active group (preliminary results) suggests that this protein might be functional in photosynthetic water oxidation. This is further supported by the fact that the isolated L-AM E has a low catalase activity. | | | |
Reference
| Z. Naturforsch. 50c, 638—651 (1995); received May 22/July 10 1995 | | | |
Published
| 1995 | | | |
Keywords
| L-Arginine Metabolizing Enzyme, Water Oxidizing Enzyme, Photosystem II, Quinoproteins | | | |
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| default:Reihe_C/50/ZNC-1995-50c-0638.pdf | | | | Identifier
| ZNC-1995-50c-0638 | | | | Volume
| 50 | |
| 32 | Author
| L. Kovács3, U. Hegdeb, S. Padhyeb, G. Bernät3, S. Demeter3 | Requires cookie* | | | Title
| Effects of Potassium-(picrate)-(18-crown-6) on the Photosynthetic Electron Transport | | | | Abstract
| The effects of potassium-(picrate)-(18-crown-6) on the electron transport of photosystem II was investigated in isolated pea thylakoids. Low concentrations of the compound inhibited the fast decay of fluorescence yield associated with electron transfer between the primary (Q a) and secondary (Q b) quinone electron acceptor and increased the intermediary level of fluorescence to the Fmax level. The decay half-time of fluorescence yield measured in the presence of D C M U (S2Q A' charge recombination) decreased from about 1.8 s to about 0.3 s in thylakoids treated with potassium-(picrate)-(18-crown-6). W hile the inhibition of electron transport by D C M U gave rise to the appearance of a thermoluminescence band at about + 10°C (S2Q A~charge recombination) addition of potassium-(picrate)-(18-crown-6) resulted in a thermoluminescence band at about -10°C. Increasing concentrations of potassium-(picrate)-(18-crown-6) diminished the fluorescence yield and the -10°C TL band and abolished the Signal II S and Signal I I f E P R signals of the tyrosine-D and tyrosine-Z electron donors, respec tively. The phenolic-type inhibitor, potassium picrate had the same effect on thermolumines cence and on the tyrosine E P R signals. It is concluded that potassium-(picrate)-(18-crown-6) is a phenolic type inhibitor owing to its picrate constituent. A t low concentrations picrate and potassium-(picrate)-18-crown) not only block the electron transport between Q A and O b but they probably decrease the midpoint redox potential of Q A, as well. A t high concen trations they also inhibit the light-induced oxidation of the tyrosine-D and tyrosine-Z donors. | | | |
Reference
| Z. Naturforsch. 51c, 539—547 (1996); received December 22 1995/ | | | |
Published
| 1996 | | | |
Keywords
| Phenolic Inhibitors, Photosynthesis, Photosystem II, Thermoluminescence, Electron Paramagnetic Resonance | | | |
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| default:Reihe_C/51/ZNC-1996-51c-0539.pdf | | | | Identifier
| ZNC-1996-51c-0539 | | | | Volume
| 51 | |
| 33 | Author
| G. H. Schmida, A. R. Adunz3, K.P B Ader3, B. Myśliwa-Kurdzielb, K. Strzał, J. Krukb | Requires cookie* | | | Title
| Action of an Antiserum to a-Tocoquinone on Photosystem II-Particle Preparations of N icotiana tabacum | | | | Abstract
| An antiserum to a-tocoquinone was prepared by immunization of rabbits. Immunization was obtained by injection of a conjugate consisting of the hapten a-tocoquinone attached to methylated ovalbumin into the rabbit. The antiserum recognizes the 3,4-dimethyl-p-benzo-quinone group of the m olecule as well as part of the immediate vicinity to the side chain. This is concluded from the fact that the antibody has som e affinity also to plastoquinone. No reaction of the antibody is observed with a-tocopherol hydroquinone or a-tocopherol. Reac tion of the antiserum to a-tocoquinone with photosystem Il-particle preparations from to bacco affects the functionality of the preparation. Chlorophylla-fluorescence emission is quenched without an alteration of the em ission spectrum. Concomitant with this fluorescence quenching, the lifetime of two fluorescence com ponents namely that of a fast and a slower component are shortened. By analogy with the literature the fast component is associated with chlorophylla of the reaction center core and that of the slow com ponent with the antenna system in which the lifetime parameter is shortened by the antibody from 3.42 ns to 1.795 ns. The action on the fast component is less and leads to a shortening of the lifetime parame ter from 0.373 ns to only 0.249 ns. The effect is interpreted in terms of an enhancement of linear photosynthetic electron transport possibly due to an inhibition of the cyclic electron transport around PS II, discovered by Gruszecki et al. | | | |
Reference
| Z. Naturforsch. 51c, 691—6 (1996); received May 14/July 17 1996 | | | |
Published
| 1996 | | | |
Keywords
| Antiserum, a-Tocoquinone, Photosystem II, Fluorescence Lifetime, Nicotiana tabacum | | | |
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| default:Reihe_C/51/ZNC-1996-51c-0691.pdf | | | | Identifier
| ZNC-1996-51c-0691 | | | | Volume
| 51 | |
| 34 | Author
| E.K N Én, N. Én, É. Th, M. F. Ragata | Requires cookie* | | | Title
| Effect of MgCl2 and Phosphatidylglycerol on CaCl2-Mediated Recovery of Oxygen Evolution in a Photosystem II Complex Depleted of the 17 and 24 kDa Extrinsic Proteins | | | | Abstract
| Phosphatidylglycerol (PG) is an anionic lipid of the thylakoid m em brane of higher plant chloroplasts. PG was shown previously to stimulate the evolution of oxygen in intact pho tosystem II (PSII) membranes [Fragata, M., Strzalka, K. and Nenonene, E. K. (1991) J. Pho-tochem. Photobiol. B: Biol 11, 329-342], In this work, a study was undertaken of the effect of MgCl2 and PG on the CaCl2-mediated recovery of oxygen evolution in a PSII complex depleted of the extrinsic proteins (EP) of molecular masses 17 kDa (EP17) and 24 kDa (EP24), hereunder designated d 1724PSII. This molecular system is structurally close to the PSII core complex of cyanobacteria and is therefore useful in the comparative analysis of PSII-PG relationships in cyanobacteria and the higher plants. This work reveals a new aspect of the thylakoid lipids role in the PSII function, namely the PG effect on intact PSII is observed as well in d 1724PSII. The results show that phosphatidylglycerol has the ability to compensate for the loss of EP17 and EP24 in the PSII complex. That is, PG restores the oxygen evolution in d 1724PSII incubated in the presence of MgCl2 and/or CaCl2 to the levels observed in native PSII. M oreover, the site of H 20 degradation in d 17 24PSII, including most probably the pool of calcium and chloride ions, would seem to be protected by phosphatidyl glycerol. This suggests that one of the docking sites of PG in the PSII complex is near EP24, inasmuch as this extrinsic protein participates in the regulation of the affinity of the calcium and chloride ions to the water oxidation site. Furtherm ore, taking into account that in d j7 24PSII the PSII core complex is directly exposed to PG, then the phospholipid effect reported here indicates that phosphatidylglycerol might be a functional effector and mem brane anchor of the D1 protein in the PSII core complex as was shown recently in the cyanobacterium Oscillatoria chalybea [Kruse, O. and Schmid, G. H. (1995) Z. Naturforsch. 50c, 380-390], | | | |
Reference
| Z. Naturforsch. 53c, 39—4 (1998); received September 1/October 24 1997 | | | |
Published
| 1998 | | | |
Keywords
| Extrinsic Proteins, Oxygen Evolution Recovery, Phosphatidylglycerol, Photosystem II, Salt-Mediated Effects | | | |
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| default:Reihe_C/53/ZNC-1998-53c-0039.pdf | | | | Identifier
| ZNC-1998-53c-0039 | | | | Volume
| 53 | |
| 35 | Author
| Jaber Rahoutei3, MatildeB. Arón3, IsabelG. Arcía-Luqueb, Magdolna Droppac, András Neményic, G. Ábor, H. Orváthc | Requires cookie* | | | Title
| Effect of Tobamovirus Infection on Thermoluminescence Characteristics of Chloroplasts from Infected Plants | | | | Abstract
| Changes of thermoluminescence characteristics as well as the 0 2-evolving capacity was analysed in chloroplasts isolated from Nicotiana benthamiana infected with pepper and pa prika mild mottle viruses and their chimeric hybrids. The electron transport activity in thyla koids of virus-infected plants was inhibited and could be restored by adding DPC or Ca2+ which indicated that the virus infection altered the oxygen-evolving complex. In thermolumi nescence characteristics of plants infected with either viruses, the first well defined response was a shift in the peak position of the B band from 20 °C to 35 °C corresponding to S3(S2)Q b-and S2Q b~ charge recombinations, respectively, which showed an inhibition in the formation of higher S states in the water splitting system. Simultaneously, a new band ap peared around 70 °C due to chemiluminescence of lipid peroxidation. Further progress of the viral infection dramatically decreased the intensity of bands originated from charge re combinations with a concomitant increase of the band at 70 °C indicating the general oxida tive breakdown of injured thylakoids. | | | |
Reference
| Z. Naturforsch. 54c, 634 (1999); received November 15 1998/January 15 1999 | | | |
Published
| 1999 | | | |
Keywords
| Biotic Stress, Photosynthetic Electron Transport, Photosystem II, Thermoluminescence, Virus Infection | | | |
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| default:Reihe_C/54/ZNC-1999-54c-0634.pdf | | | | Identifier
| ZNC-1999-54c-0634 | | | | Volume
| 54 | |
| 36 | Author
| Sándor Dulai3, István Molnár3, Evelin Pélia, Endre Lehoczkiab | Requires cookie* | | | Title
| Short-Term Responses of Photosystem II to Heat Stress in Cold-Acclimated Atrazine-Resistant and Susceptible Biotypes of Erigeron canadensis (L.) | | | | Abstract
| When leaves of atrazine-resistant (A R) and atrazine-sensitive (S) Erigeron canadensis (L.) plants grown at 5 °C were exposed to an elevated temperature (35 °C) for 30 min, the critical (T c) and peak temperatures (Tp) of the F0 vs. T curves were considerably higher for the leaves of the S biotype, but not for those of the A R biotype. The temperature dependences of F J F m and AFIFm' were not greatly different for the heat-treated cold-acclimated A R biotype, in contrast with the situation for the S plants. This short-term heat treatment resulted in a more significant shift in the optimal thermal interval of C 0 2 fixation for the S than for the A R biotypes. | | | |
Reference
| Z. Naturforsch. 54c, 665 (1999); received November 2 1998/February 19 1999 | | | |
Published
| 1999 | | | |
Keywords
| Erigeron canadensis, Heat Stress, Chlorophyll Fluorescence, Photosystem II, Photosynthesis | | | |
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| default:Reihe_C/54/ZNC-1999-54c-0665.pdf | | | | Identifier
| ZNC-1999-54c-0665 | | | | Volume
| 54 | |
| 37 | Author
| Merope Tsimilli-Michaelab, Martin Pêcheux3, RetoJ. Strasser3 | Requires cookie* | | | Title
| Light and Heat Stress Adaptation of the Symbionts of Temperate and Coral Reef Foraminifers Probed in Hospite by the Chlorophyll a Fluorescence Kinetics | | | | Abstract
| Since the early 80's massive bleaching affects the reef ecosystem. It involves, besides corals, several other species among which large foraminifers, and it corresponds to the loss of their photosynthetic symbionts or the symbionts' pigments. The cause is unclear, though temper ature elevation and strong irradiation have been considered to be primary factors. In this work we investigated in two genera of coral reef foraminifers (Amphistegina lobifera and Amphisorus heimprichii) and in the temperate foraminifer Sorites variabilis the response of photosystem II (P SII) of their symbionts in hospite upon light stress (white light of 550 |aE n r 2 s_1 and red light of 3200 |iE m~2 s" 1) and heat stress (up to 32 °C), by means of the Chla fluorescence transients O -J-I-P they exhibit upon illumination. The transients were analysed according to the JIP-test which leads to the calculation of several structural and functional parameters providing a quantification of PSII behaviour. We observed that the various parameters undergo modifications that differ concerning both their extent and their degree of elasticity, thus indicating that different adaptive strategies are employed in response to stress. The most pronounced of these regulatory changes is a wide decrease of the quantum yield of electron transport. However, the extent of the changes, different for the three studied species, was in general smaller when the cultures were kept under low light (70 ^iE m -2 s-1) than in darkness. By the applied stressors, PSII was not damaged and, except for some cells in which an expulsion of symbionts was initiated, no bleaching was observed. This can be well correlated with the observed adaptability of PSII. As a working hypothesis, it is proposed that the decrease of the capacity for electron transport activity might be among the factors trigger ing bleaching in the field. | | | |
Reference
| Z. Naturforsch. 54c, 671 (1999); received November 10 1998 | | | |
Published
| 1999 | | | |
Keywords
| Coral-Reef Bleaching, Electron Transport Activity, JIP-test, Photosystem II, Thermoprotection | | | |
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| default:Reihe_C/54/ZNC-1999-54c-0671.pdf | | | | Identifier
| ZNC-1999-54c-0671 | | | | Volume
| 54 | |
| 38 | Author
| Salil Bose, R. M. Annar, M. Annan, C. J. Arntzen | Requires cookie* | | | Title
| Increased Synthesis of Photosystem II in Triticum vulgare when Grown in the Presence of BAS 13-338 | | | | Abstract
| Addition o f BAS 13-338 (4-chloro-5-dim ethylam ino-2-phenyl-3(2H)-pyridazinone) to a sus pension o f chloroplast thylakoids caused an increase in the / level o f chlorophyll fluorescence induction without affecting the F0 level and with a slight decrease in the Fmax level in a manner similar to the addition o f D C M U to a thylakoid suspension. A ddition o f BAS 13-338 also inhibited the rate o f Hill reaction H20 -» dichlorophenol indophenol with 50% inhibition occurring at about 10 hm BAS 13-338. The inhibition was not reversed by diphenyl carbazide used as an artificial electron donor to photosystem II. These results suggest that the site o f in h ib i tion by BAS 13-338 is between Q (next to the primary electron acceptor) and plastoquinone. When the plants were grown in the presence o f sublethal dose o f BAS 13-338, the follow ing changes were noted in the thylakoids o f the treated plants as com pared to the thylakoids isolated from the control plants: The F0 and the norm alized variable fluorescence (4F/F0) levels increased, chlorophyll a/b ratio decreased, chlorophyll/P 700 ratio increased. Furthermore, the rate o f photosystem II electron transport both under saturated intensity and the lim iting intensity of illumination increased, and the ratio o f plastoquinone to Q decreased. These observations have been interpreted as due to an increase in the ratio o f photosystem II to photosystem I in plants grown in the presence o f BAS 13-338. | | | |
Reference
| Z. Naturforsch. 39c, 510 (1984); received D ecem ber 1 1983 | | | |
Published
| 1984 | | | |
Keywords
| Photosynthesis, Electron Transport, Chlorophyll Fluorescence, Photosystem II, BAS 13-338 | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0510.pdf | | | | Identifier
| ZNC-1984-39c-0510 | | | | Volume
| 39 | |
| 39 | Author
| Jean-M Arc, D. Ucruet, Rene Scalla | Requires cookie* | | | Title
| Action of Methylthiopyrimidine Experimental Herbicides as Diuron-Like Inhibitors of Photosynthesis | | | | Abstract
| Derivatives of 6-chloro-5-methylthiopyrimidines provide potent inhibitors of the photosynthe tic electron flow, which act like Diuron on fluorescence induction kinetics and competitively displace it from its binding site. Structure-activity relationships show that, unlike triazines, ac tivities of 2-or 4-alkylamino derivatives are restricted by steric hindrances. Decreases in inhibit ory activities of these compounds observed in triazine-resistant chloroplasts are lower than de creases reported for triazines themselves. | | | |
Reference
| Z. Naturforsch. 40c, 388 (1985); received October 31 1984/February 1 1985 | | | |
Published
| 1985 | | | |
Keywords
| Methylthiopyrimidines, Diuron-Like Inhibitors, Photosynthesis, Structure-Activity Correlations, Photosystem II | | | |
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| default:Reihe_C/40/ZNC-1985-40c-0388.pdf | | | | Identifier
| ZNC-1985-40c-0388 | | | | Volume
| 40 | |
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