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  • 1
    Electronic Resource
    Electronic Resource
    Phototaxis, gravitaxis and vertical migrations in the marine dinoflagellate Prorocentrum micans (1991)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 8 (1991), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1991.tb01777.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of solar radiation and solar radiation deprived of UV-B and total UV on photosynthetic oxygen production and pulse amplitude modulated fluorescence in the brown alga Padina pavonia (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 19 (1996), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: The effects of solar radiation on photosynthetic oxygen production and pulse amplitude modulated (PAM) fluorescence were measured in the marine brown macroalga Padina pavonia harvested from different depths from the Greek coast near Korinth. In fluence rate-response curves the light compensation point for photosynthetic oxygen production increased and the saturation level decreased with increasing exposure time to solar radiation. Cutting off the UV-B wavelength range (280–315 nm) from solar radiation reduced the inhibition of photosynthesis, and the organisms were less affected when all of the UV radiation was filtered out. Algae collected from 7 m depth were much more prone to photoinhibition than those harvested from rock pools exposed to unfiltered solar radiation. During continuous exposure to solar radiation, rock pool algae showed photoinhibition after longer periods of time than specimens from 7 m or from dark adapted habitats. When subjected to unfiltered solar radiation the ratio of the variable fluorescence to the maximal fluorescence 〈inlineGraphic alt="inline image" href="urn:x-wiley:01686496:FEM53:FEM_19_mu1" location="equation/FEM_19_mu1.gif"/〉 (Fv = Fm− Fo) rapidly declined with increasing exposure time. However, again algae from 7 m depth were more prone to photoinhibition than rock pool algae. The differences between the two ecological strains were less obvious when UV-B or total UV was removed from solar radiation. Only in the latter case a complete recovery was observed after 2 h while, when exposed to unifiltered sunlight, only the rock pool algae recovered completely within that time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1996.tb00198.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of enhanced UV-B irradiation on the red coloured freshwater flagellate Euglena sanguinea (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 13 (1994), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Euglena sanguinea, a freshwater flagellate isolated from a pond in the Fränkische Schweiz, orients itself in its habitat exclusively by positive phototaxis, which leads the organisms to the surface where they form a neuston. The algae are coloured red, as they contain haematochrome, a mixture of carotenoids, the main component being astaxanthin diester. Absorption spectroscopy shows that astaxanthin diester accumulates in cells irradiated with artificial UV-B irradiation, which suggests that the carotenoid is a photoprotective pigment. 15% enhanced UV-B irradiation impairs photoorientation and motility and photobleaches chlorophyll a while the carotenoids are less affected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1994.tb00064.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of tropical solar radiation on the motility of filamentous cyanobacteria (1993)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 12 (1993), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effects of tropical solar radiation on the motility of the cyanobacteria Anabaena variabilis, Oscillatoria tenuis and two strains of Phormidium uncinatum were studied in Ghana (4.30°N). The percentages of motile filaments were drastically reduced by unfiltered solar radiation. Covering the organisms with various long pass or band pass filters (WG320, GG395 or UG5) revealed that the UV-B, UV-A and visible light components of the solar spectrum were all effective in impairing motility in these organisms. Only partial recovery was observed and only after short exposure times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1993.tb00026.x
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  • 5
    Electronic Resource
    Electronic Resource
    Orientation of Paramecium Under the Conditions of Weightlessness (1993)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 40 (1993), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . A cell culture of Paramecium with a precise negative gravitaxis was exposed to 4 times 10-6g during a parabolic flight of a sounding rocket for 6 min. Computer image analysis revealed that without gravity stimulus the individual swimming paths remained straight. In addition, three reactions could be distinguished. For about 30 s, paramecia maintained the swimming direction they had before onset of low gravity. During the next 20 s, an approximate reversal of the swimming direction occurred. This period was followed by the expected random swimming pattern. Similar behavior was observed under the condition of simulated weightlessness on a fast-rotating clinostat. Control experiments on the ground under hyper-gravity on a low-speed centrifuge microscope and on a vibration test facility proved that the observed effects were caused exclusively by the reduction of gravity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1993.tb04937.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of solar and ultraviolet radiation on motility, photomovement and pigmentation in filamentous, gliding cyanobacteria (1991)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 9 (1991), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1991.tb01748.x
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of enhanced solar irradiation on chlorophyll fluorescence and photosynthetic oxygen production of five species of phytoplankton (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 16 (1995), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effects of solar irradiation on chlorophyll a fluorescence and photosynthetic oxygen production of three Cryptomonas species, Euglena gracilis and Scenedesmus cf. quadricauda were investigated in comparative field studies in Erlangen (280 m above sea level) and at Zugspitze (2957 m above sea level). The experiments showed that the decrease of fluorescence and the inhibition of photosynthetic oxygen production occurred after shorter times of exposure to solar radiation at Zugspitze compared to Erlangen in all tested organisms. Cryptomonas maculata was more sensitive towards radiation than the other organisms: fluorescence decreased earlier, while Scenedesmus cf. quadricauda seemed to be much less sensitive since fluorescence and photosynthetic oxygen production decreased later and to a smaller extent compared to the other organisms. The results of the present study indicate that increased solar radiation (with an increased level of UV-B radiation) at higher geographical altitudes may have significant effects on phytoplankton populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1995.tb00266.x
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  • 8
    Electronic Resource
    Electronic Resource
    UV effects on photosynthesis and phycobiliprotein composition in the flagellate Cyanophora paradoxa (1992)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 10 (1992), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effects of solar and artificial ultraviolet radiation on photosynthetic oxygen production and phycobiliprotein composition were investigated in the freshwater flagellate, Cyanophora paradoxa. The phycobiliproteins of the cell acting as photosynthetic accessory pigments were found to be readily affected by even short exposure to ultraviolet radiation, while the membrane-bound chlorophyll protein complexes were hardly impaired as demonstrated by SDS polyacrylamide gel electrophoresis, isoelectric focussing and fast protein liquid chromatography (FPLC). The phycobilisomes are dissembled from the outside inwards and go from higher molecular weight components to hexamers (αβ)6, trimers (αβ)3 and finally monomers (αβ). Fluorescence spectra indicated that the energy transfer from accessory pigments to the photosystems was impaired by ultraviolet radiation. Photosynthetic oxygen production was affected on a much faster timescale than changes in the absorption spectra or at the protein level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1992.tb00006.x
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  • 9
    Electronic Resource
    Electronic Resource
    Ultraviolet radiation induces both degradation and synthesis of phycobilisomes in Nostoc sp.: a spectroscopic and biochemical approach (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 23 (1997), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A cyanobacterium, Nostoc sp., isolated from an Andean lake located 3980 m above sea level (Cusco, Peru) was used for this study. Phycobilisomes, the light-harvesting complexes of photosystem II in cyanobacteria, were isolated and their components, allophycocyanin, phycocyanin and phycoerythrin, characterized using absorption spectroscopy, chromatography, SDS-PAGE, and 2D-PAGE. When immobilized cells in agarose were exposed to ultraviolet radiation, the photobleaching of phycobilisomes took place with a faster kinetics than that of chlorophyll a and carotenoids. Isolated thylakoid membranes exposed to ultraviolet radiation confirmed the rapid degradation of phycobilisomes. Nostoc cells were irradiated with UV and the phycobilisomes isolated and analyzed. During the first 15 min of ultraviolet radiation, phycobilisomes were degraded followed by an increase in phycobiliproteins after 30 min (P〈0.05), which was maintained until 45 min of exposure; then the concentration decreased again. Changes in the composition of the phycobilisome rods were observed; absorption spectroscopy indicates a partial depletion of phycocyanin; 2D gels showed that the isoelectric point of phycocyanin was affected indicating effects of ultraviolet radiation at the amino acid level. The clonogenic capacity of the cells was not significantly affected even after 30 min of exposure (P〈0.01).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1997.tb00411.x
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of solar and ultraviolet radiation on motility, photomovement and pigmentation in filamentous, gliding cyanobacteria (1991)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 86 (1991), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effects of solar irradiation and artificial UV irradiation on several cyanobacteria (Anabaena variabilis and two strains of Phormidium uncinatum) have been studied. Both types of radiation affect the percentage of motile filaments and impair the linear velocity of the organisms. Long term exposure to UV radiation bleaches the photosynthetic pigments as determined by absorption difference spectra. Fluorescence excitation and emission spectra indicate that under ultraviolet radiation the energy transfer from the accessory pigments to chlorophyll is affected. Furthermore the structural integrity of the phycobilisomes seems to be impaired by continuous radiation and the photoreceptor pigments seem to be destroyed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1991.tb04805.x
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