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  • 1
    Electronic Resource
    Electronic Resource
    Effects of abiotic stresses on the turnover of the D1 reaction centre II protein (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 101 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the 1990's, evidence has accumulated that various unfavourable environmental conditions substantially affect the turnover of the D1 protein of reaction centre II, the psb A gene product. Biochemical, molecular and physiological studies in higher plants indicate that alterations of D1 protein turnover occur under drought, nutrition deficiency, heat, chemical stress, ozone fumigation as well as UV-B and visible photo-stresses. The behaviour of photosystem II under these various stress conditions indicates that the response of D1 protein turnover can be interpreted as a general adaptive response to environmental extremes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb01048.x
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  • 2
    Electronic Resource
    Electronic Resource
    Involvement of protein phosphorylation in the sensitivity of photosystem II to strong illumination (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 92 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Four types of differently phosphorylated hylakoids isolated from field grown spinach (Spinacia oleracea L.) were tested for the sensitivity of photosystem II (PSII) to photoinactivation. Phosphorylation of light-harvesting II complexes (LHCII) protected PSII electron transfer from photoinhibitory damage, while the phosphorylation of the PSII core polypeptides slightly accelerated the decline of electron transfer during high irradiance treatment. Dephosphorylation of the CP43 apoprotein and PsbH protein by an alkaline phosphatase resulted in an extreme sensitivity of the thylakoids to strong illumination. The PSII photoinactivation of thylakoids with the impaired oxygen-evolving complex was found to be independent of phosphorylation.The thylakoids of the thermophilic cyanobacterium Synechococcus elongates were used in order to compare the plants with an organism where LHCII complexes are missing and the PSII core proteins are not phosphorylated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb06669.x
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  • 3
    Electronic Resource
    Electronic Resource
    Photoadaptation of two members of the Chlorophyta (Scenedesmus and Chlorella) in laboratory and outdoor cultures: changes in chlorophyll fluorescence quenching and the xanthophyll cycle (1999)
    Springer
    Planta 209 (1999), S. 126-135 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Chlorella ; Electron transport rate ; Non-photochemical quenching ; Photosynthesis ; Scenedesmus ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The role of the xanthophyll cycle in the adaptation of two chlorococcal algae Scenedesmus quadricauda and Chlorella sorokiniana to high irradiance was studied under laboratory and outdoor conditions. We wished to elucidate whether the xanthophyll cycle plays a key role in dissipating the excesses of absorbed light, as in higher plants, and to characterise the relationship between chlorophyll fluorescence parameters and the content of xanthophyll-cycle pigments. The xanthophyll cycle was found to be operative in both species; however, its contribution to overall non-photochemical quenching (NPQ) could only be distinguished in Scenedesmus (15–20% of total NPQ). The Scenedesmus cultures showed a larger pool of xanthophyll-cycle pigments than Chlorella, and lower sensitivity to photoinhibition as judged from the reduction of maximum quantum yield of photosystem II. In general, both algae had a larger xanthophyll-cycle pool when grown outdoors than in laboratory cultures. Comparing the two species, Scenedesmus exhibited a higher capacity to adapt to high irradiance, due to an effective quenching mechanism and high photosynthetic capacity; in contrast, Chlorella represents a species with a larger antennae system, less-efficient quenching and lower photosynthetic performance. Non-photochemical quenching (NPQ) induced through the xanthophyll cycle can, to a limited extent, represent a regulatory factor in diluted algal cultures grown in outdoor solar photobioreactors, as well as in natural algal phytoplankton populations exposed transiently to high irradiance. However, it does not play an appreciable role in dense, well-mixed microalgal suspensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050614
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  • 4
    Electronic Resource
    Electronic Resource
    In situ monitoring of chlorophyll fluorescence to assess the synergistic effect of low temperature and high irradiance stresses inSpirulina cultures grown outdoors in photobioreactors (1996)
    Springer
    Journal of applied phycology 8 (1996), S. 283-291 
    Details
    ISSN: 1573-5176
    Keywords: fluorescence ; photoinhibition ; photosynthesis ; Spirulina ; photobioreactor ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A chlorophyll fluorescence technique was applied to anin situ study on the effects of low temperature and high light stresses onSpirulina cultures grown outdoors in controlled tubular photobioreactors at high (1.1 g L−1) and low (0.44 g L−1) biomass concentrations. Diurnal changes in PSII photochemistry (F v/F m) after 15 min of darkness, or in the light (dF/F′ m), and non-photochemical (qN) quenching were measured using a portable, pulse-amplitude-modulated fluorometer. The depression of theF v/F m ratio ofSpirulina cultures grown outdoors at 25°C (i.e. 10°C below optimum for growth) and 0.44 g L−1, reached 30% at the middle of the day. At the same time of the day thedF/F′ m ratio showed a reduction of up to 52%. The depression of bothF v/F m anddF/F′ m was lower in the cultures grown at 1.1 g L−1. Photoinhibition reduced the daily productivity of the culture grown at 0.44 g L−1 and 25°C by 33% with respect to that grown at 35°C. Changes in the growth yields of the cultures grown under different temperatures and growth rates correlate well with analogous changes in photon yield (dF/F′ m). Simple measurements of photochemical yield (F v/F m) can be used to test the physiological status ofSpirulina cultures. The results indicate that the saturating pulse fluorescence technique, when usedin situ, is a powerful tool for assessment of the photosynthetic characteristics of outdoor cultures ofSpirulina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02178571
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  • 5
    Electronic Resource
    Electronic Resource
    Three types of Photosystem II photoinactivation (1990)
    Springer
    Photosynthesis research 24 (1990), S. 89-97 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll a fluorescence ; D1 protein ; oxygen evolving Photosystem II particles ; pheophytin ; photoinactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oxygen evolving Photosystem II particles were exposed for up to 10 h to 100 W m-2 white light at 20°C under aerobic, low oxygen, strictly anaerobic and strongly reducing conditions. The fast and slow photoinactivation processes described earlier (Šetlík et al. 1989) were observed during the first 120 min. The third and by far the slowest process impaired the primary charge separation P680+−Pheo−. Its half-time was about 2.5 h under aerobic and strongly reducing conditions and about 4 h under anaerobic and low oxygen conditions. In these time intervals there were no changes in the chlorophyll-protein and polypeptide composition of the particles irradiated under anaerobic, low oxygen or strongly reducing conditions while a dramatic degradation of chlorophyll-proteins and polypeptides occurred under aerobic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00032648
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of Photosystem II inhibitors DCMU and BNT on the high-light induced D1 turnover in two cyanobacterial strains Synechocystis PCC 6803 and Synechococcus PCC 7942 (1998)
    Springer
    Photosynthesis research 57 (1998), S. 193-202 
    Details
    ISSN: 1573-5079
    Keywords: herbicides ; photoinhibition ; photosynthesis ; protein degradation and synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of the Photosystem II (PSII) inhibitors dichlorophenyldimethylurea (DCMU) and bromonitrothymol (BNT) on the rate of the high-light induced D1 protein turnover was studied in whole cells of two cyanobacterial strains Synechocystis PCC 6803 and Synechococcus PCC 7942. In Synechocystis the D1 degradation was slowed down to a similar extent in the presence of either inhibitor compared with control cells. This slower degradation corresponded with the retardation of Photosystem II photoinactivation (PSIIPI) measured as a decline of PS II activity in the illuminated cells treated with chloramphenicol (CAP). The ongoing D1 synthesis in the presence of both PS II inhibitors was confirmed by unchanging PS II activity and the steady-state level of D1 during illumination in the absence of CAP. In Synechococcus cells both DCMU and BNT blocked the turnover of the 'low-light' D1 form (D1:1) but did not prevent the exchange of the 'high-light' form D1:2 for the D1:1 form. The similar effect of both herbicides on the D1 exchange was in contrast with their influence on the rate of PSIIPI. While DCMU had a pronounced protective effect, BNT significantly increased the rate of PS II photodamage. The fast BNT-induced decline of PS II activity was also observed in Synechocystis cells treated with azide, an inhibitor of reactive oxygen species scavenging enzymes. Therefore, we assume that the distinct sensitivity of the two cyanobacterial strains to BNT can be caused by different content and/or activity of these enzymes in each strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006015214868
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  • 7
    Electronic Resource
    Electronic Resource
    A sensitive photosystem II-based biosensor for detection of a class of herbicides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 664-669 
    Details
    ISSN: 0006-3592
    Keywords: herbicides ; photosystem II ; thermophilic cyanobacteria ; biosensor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have developed a biosensor for the detection of residual triazine-, urea- and phenolic-type herbicides, using isolated photosystem II (PSII) particles from the thermophilic cyanobacterium, Synechococcus elongatus, as biosensing elements. The herbicide detection was based on the fact that, in the presence of artificial electron acceptors, the light-induced electron transfer through isolated PSII particles is accompanied by the release of oxygen, which is inhibited by the herbicide in a concentration-dependent manner. The PSII particles were immobilized between dialysis membrane and the Teflon membrane of the Clark oxygen electrode mounted in a flow cell that was illuminated. Inclusion of the antibiotic chloramphenicol in the reaction mixtures prolonged, by 50%, the lifetime of the biosensor. The use of highly active PSII particles in combination with the flow system resulted in a reusable herbicide biosensor with good stability (50% of initial activity was still remaining after 35-h use at 25°C) and high sensitivity (detection limit for diuron was 5 × 10-10 M). © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 664-669, 1998.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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