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1Author    K. H. GrumbachRequires cookie*
 Title    Interconversion of Carotenoids and Quinones after Onset of Photosynthesis in Chloroplasts of Higher Plants  
 Abstract    The interconversion of carotenoids and quinones was investigated in beech and spinach leaves as well as isolated intact spinach chloroplasts following a dark-light transition. It is shown that isolated intact chloroplasts which are preincubated for 2 h at pH 7.6 in the dark and re­ illuminated with strong white light are capable not only o f deepoxidizing violaxanthin into antheraxanthin and zeaxanthin but simultaneously change the redox state o f the plastoquinone-pool in their thylakoid membrane. At the same time as violaxanthin is deepoxidized plasto-hydroquinone-9 is oxidized to plastoquinone-9. If the light is turned off zeaxanthin is epoxidized into antheraxanthin and violaxanthin but no significant change in the redox state o f the plasto-quinone-pool occurred. It is concluded that the deepoxidation of violaxanthin is connected to the photosynthetic electron transport in that way that an acidification o f the intrathylakoidal compartment by the vectorial release of protons from the water photooxidizing enzyme system and the plastoquinone-pool is required for the activation of the violaxanthin deepoxidase. This may be taken as further evidence that violaxanthin deepoxidase is located at the inner side o f the thylakoid membrane. Additional evidence for this location site is given by the observation that neither deepoxidation of violaxanthin nor photooxidation of plastohydroquinone-9 occurred after onset o f photosyn­ thesis if non cyclic electron transport was inhibited by DCMU. 
  Reference    Z. Naturforsch. 38c, 393 (1983); received March 15 1983 
  Published    1983 
  Keywords    Carotenoids, Photosynthesis, Quinones, Xanthophyll Cycle 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0393.pdf 
 Identifier    ZNC-1983-38c-0393 
 Volume    38 
2Author    WieslawI. Gruszecki, ZbigniewK. RupaRequires cookie*
 Title    Changes of Excitation Spectra of in vivo Chlorophyll Fluorescence during Induction of Photosynthesis  
 Abstract    Excitation spectra of chlorophyll fluorescence from intact rye leaves were registered at dif­ ferent steps of the induction of photosynthesis after dark adaptation. Analysis of these spectra indicates that at least two processes related to spectroscopic features are responsible for a flu­ orescence quenching. The first one, active during the first 100 s of illumination, was interpret­ ed to consists in an overall decrease of the fluorescence quantum yield of antenna pigments and chlorophylls, in particular close to the reaction centers. The second type of a fluorescence decrease (between 100 s and 300 s o f illumination) was found to be in large extent related to decrease of the rate of an excitation energy transfer between accessory xanthophyll pigments and chlorophylls emitting fluorescence. This latter molecular mechanism is discussed as being related to violaxanthin availability to de-epoxidation in the xanthophyll cycle. 
  Reference    Z. Naturforsch. 48c, 46—51 (1993); received September 21/December 31 1992 
  Published    1993 
  Keywords    Chlorophyll Fluorescence, Photosynthesis, Violaxanthin, Xanthophyll Cycle 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0046.pdf 
 Identifier    ZNC-1993-48c-0046 
 Volume    48 
3Author    F. Rank Terjung, K. Arlheinz, M. AierRequires cookie*
 Title    Nonphotochemical Quenching of Chlorophyll Fluorescence in Higher Plant Leaves Studied by Delayed Fluorescence Decay Measurements  
 Abstract    Delayed chlorophyll fluorescence decay measurements on the second time scale were ap­ plied to investigate the state of photosystem II under different photosynthetic conditions. Leaves adapted to high and low light intensities were used to study the effects of nonphoto­ chemical quenching (energy quenching) on the photosynthetic state. 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCM U)-treated leaves were used to characterize the photosynthetic state in the absence of a transthylakoid ApH, dithiothreitol (D TT)-treated leaves in the absence of the xanthophyll zeaxanthin. The fast decay components were the most affected by energy quenching as indicated by increased decay times. The slowest decay com ponent was hardly affected, neither in amplitude nor in decay time. The measurem ents indicate a relaxation of energy quenching on the second time scale and the absence of damages in the electron transfer chain of PS II. The constant decay times of the DTT-treated leaf, com parable to those of the DCM U-treated leaf, indicate the obligatory role of zeaxanthin for most of the detected energy quenching. 
  Reference    Z. Naturforsch. 53c, 27—32 (1998); received October 9/October 31 1997 
  Published    1998 
  Keywords    Delayed Fluorescence, Energy Quenching, Pisum sativum, Xanthophyll Cycle 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0027.pdf 
 Identifier    ZNC-1998-53c-0027 
 Volume    53 
4Author    Carina Barth, G.Heinrich KrauseRequires cookie*
 Title    Inhibition of Photosystems I and II in Chilling-Sensitive and Chilling-Tolerant Plants under Light and Low-Temperature Stress  
 Abstract    The responses of photosystems (PS) I and II to light stress at 4 °C and 20 °C were studied in leaf discs from three chilling-sensitive plant species, Cucumis sativus, Cucurbita maxima and Nicotiana tabacum, and in the chilling-tolerant Spinacia oleracea. The chilling-sensitive plants were grown at 24 °C under 8 0 -1 2 0 j.imol photons m-2 s-1 (Cucumis and Cucurbita) or 30 [imol photons m -2 s_1 (Nicotiana). Spinacia was cultivated outdoors during winter and early spring. The P700 absorbance change around 820 nm served as a relative measure of PSI activity. The potential efficiency of PSII was determined in dark-adapted leaf discs by means of the ratio of variable to maximum chlorophyll (Chi) a fluorescence emission (F v/ F m). In Cucurbita, Nicotiana and Spinacia, PSI was not or only slightly inhibited by 2 h illumination with 200 [imol m-2 s-1 at 4 °C or with 2000 ^imol m-2 s-1 at 20 °C. In leaves of Cucurbita and Nicotiana, exposure to 2000 j.imol photons m -2 s_1 at 4 °C resulted in a decline in PSI activity and potential PSII efficiency approximately to the same extent (about 50% within 2 h). In contrast, in Cucumis, both moderate and high light at low temperature caused a PSI inhibition that proceeded considerably faster than the decline in PSII efficiency. Such preferential photoinhibition of PSI was not observed in the other three species tested. In Spinacia, a lower susceptibility of PSI and PSII to photoinhibition at 4 °C was associated with a faster de-epoxidation kinetics of violaxanthin, as compared to the three chilling-sensi-tive species. In addition, leaves of Spinacia were characterized by a significantly larger pool of xanthophyll-cycle pigments and a higher content of ß-carotene based on Chi a+b. When leaves of Cucurbita were preincubated with methylviologen, which catalyzes formation of superoxide anion radicals at the acceptor side of PSI, the decline in potential PSII efficiency under 2000 jimol photons m -2 s_1 at 20 °C and 4 °C was strongly enhanced, whereas the P700 signal was less affected. Our data demonstrate that in the species tested, PSI may be inhibited in vivo besides PSII under light stress, but preferential photoinhibition of PSI is not a general phenomenon in chilling-sensitive plants. At low temperatures, a reduced function of the xanthophyll cycle and of the antioxidative scavenging system might account for enhanced PSI and PSII inhibition in vivo. 
  Reference    Z. Naturforsch. 54c, 645 (1999); received November 8 1998/January 30 1999 
  Published    1999 
  Keywords    Active Oxygen Species, Chlorophyll Fluorescence, P700 Absorbance Change, Photoinhibition, Xanthophyll Cycle 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0645.pdf 
 Identifier    ZNC-1999-54c-0645 
 Volume    54 
5Author    W. I. Gruszecki3, K. Strzałkab, A. R. Adunzc, J. K. Rukb, G. H. SchmidcRequires cookie*
 Title    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?  
 Abstract    Light-driven electron transport in liposom e-bound photosystem II (PS-II) particles be­ tween water and ferricyanide was monitored by bare platinum electrode oxymetry. The m odi­ fication of the experimental system with the exogenous quinones a-tocopherol quinone (a-TQ) or plastoquinone (PQ) resulted in a pronounced effect on photosynthetic oxygen evolution. The presence o f a-tocopherolquinone (a-T Q) in PS-II samples decreased the rate of red light-induced oxygen evolution but increased the rate o f 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 o f the oxygen signal. These findings are interpreted in terms of a cyclic electron transport around PS-II, regulated by an excitation state of ß-carotene in the reaction centre of PS-II. A mechanism is postulated according to which energetic coupling of ß-carotene in the reaction centre of PS-II and that o f other antenna carotenoid pigments is regulated by the portion of the xanthophyll violaxanthin, which is under control of the xanthophyll cycle. 
  Reference    Z. Naturforsch. 50c, 61—6 (1995); received June 15/November 11 1994 
  Published    1995 
  Keywords    a-Tocopherol Quinone, Plastoquinone-9, Oxygen Evolution, Photosystem II, Cyclic Electron Transport, Xanthophyll Cycle 
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 TEI-XML for    default:Reihe_C/50/ZNC-1995-50c-0061.pdf 
 Identifier    ZNC-1995-50c-0061 
 Volume    50 
6Author    W.I G Ruszeckia, K. Strzałk, K.P B Ad Erc, A. R. Adunzc, G. H. SchmRequires cookie*
 Title    Involvement of the Xanthophyll Cycle in Regulation of Cyclic Electron Flow around Photosystem II  
 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 photosyn­ thetic apparatus by light is under control of the xanthophyll cycle. The combination of dif­ ferent light quality and thylakoids having various levels o f xanthophyll cycle pigments were applied to support this hypothesis. In the present work photosynthetic oxygen evolution from isolated tobacco chloroplasts was measured by means o f 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 o f light-induced oxygen uptake indicate that the de-epoxidation o f 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. 
  Reference    Z. Naturforsch. 51c, 47 (1996); received September 22/O ctober 18 1995 
  Published    1996 
  Keywords    Xanthophyll Cycle, Cyclic Electron Flow, Photosystem II, Oxygen Evolution, Blue Light Effect, Mass Spectrometry 
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 TEI-XML for    default:Reihe_C/51/ZNC-1996-51c-0047.pdf 
 Identifier    ZNC-1996-51c-0047 
 Volume    51