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  • Phototaxis  (13)
  • Blue-green algae  (7)
  • Life and Medical Sciences  (6)
  • Phobic response  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    Role of three basic light reactions in photomovement of desmids (1977)
    Springer
    Planta 137 (1977), S. 207-214 
    Details
    ISSN: 1432-2048
    Keywords: Desmids ; Light trap method ; Microcinematography ; Photokinesis ; Photophobic reaction ; Phototaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoaccumulations in light trap experiments have been studied in the desmids, Cosmarium, Micrasterias and Euastrum. Dependence of accumulation density on exposure time follows saturation curves, while dose response curves show optima. Time-lapse microcinematography and population methods have revealed that all three basic light-induced motor responses known in microorganisms participate in producing photoaccumulations in desmids. During the initial phase the cells are phototactically attracted towards the trap by scattered light. In low light intensity traps photokinetic reactions may play only a minor role, since photokinesis could be evoked only by light intensities≧100 lx in Cosmarium cucumis. True photophobic reactions have been demonstrated for the first time in desmids. There are two types of phobic responses in desmids: either the cell reverses its movement or it swings sidewise into the new direction. Behaviour of partially shadowed cells suggests that perception of light direction is brough about by simultaneous intensity measurement at two or more sites within the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388152
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  • 2
    Electronic Resource
    Electronic Resource
    Wavelength dependence of photomovement in desmids (1979)
    Springer
    Planta 145 (1979), S. 1-5 
    Details
    ISSN: 1432-2048
    Keywords: Desmids ; Phobic response ; Photoaccumulation ; Photokinesis ; Phototaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The action spectra of phototaxis, photokinesis, and photophobic response of Cosmarium cucumis, C. botrytis, C. margaritiferum, and Micrasterias denticulata show peaks in the blue (about 440 nm) and red (about 670 nm) spectral regions and thus indicate the involvement of photosynthetic pigments. According to the differences in the action spectra, light-induced movement responses may be linked with photosynthesis in different ways. Results with population methods have been supported by time-lapse microcinematography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379921
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  • 3
    Electronic Resource
    Electronic Resource
    Participation of two photosystems in the photo-phobotaxis ofPhormidium uncinatum (1974)
    Springer
    Archives of microbiology 96 (1974), S. 255-266 
    Details
    ISSN: 1432-072X
    Keywords: Cyanophyceae ; Phototaxis ; Phobotaxis ; Photosynthesis ; Electron Transport Chain ; Inhibitors ; Action Spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. A hypothesis based on the Hill-Bendall-model of photosynthetic electron transport is proposed to explain positive and negative photo-phobotaxis inPhormidium uncinatum. In the non-cyclic electron chain a pool is located into which photosystem II (e. g. by absorption by C-phycoerythrin, 561 nm) feeds electrons while photosystem I (e.g. 723 nm) drains electrons out of it. 2. Interruption of the electron flow into the pool causes a sudden decrease of the pool size and thus a positive phobic response. This happens e.g. when an organism leaves a trap which is illuminated by a wavelength absorbed by photosystem II pigments (e. g. 561 nm). 3. A negative reaction takes place when electrons are suddenly drained out of the pool; again the pool size decreases. This is the case when an organism enters a light trap illuminated by photosystem I light (723 nm). 4. The net flow of electrons into or out of the pool—and thus the reaction sense—can be manipulated by the relative excitation of the two photosystems or by blocking the electron influx by DCMU.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00590181
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  • 4
    Electronic Resource
    Electronic Resource
    Extracellular and intracellular determination of light-induced potential changes during photophobic reactions in blue-green algae (1978)
    Springer
    Archives of microbiology 119 (1978), S. 75-79 
    Details
    ISSN: 1432-072X
    Keywords: Blue-green algae ; Light-induced potential changes ; Phormidium uncinatum ; Photophobic response ; Sensory transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light-induced potential changes have been measured in the filamentous blue-green alga Phormidium uncinatum both intracellularly and between the two ends of a trichome. There is evidence that these potential changes are correlated with photophobic reactions in this organism. 1. The potential changes follow the light-dark regime with a lag phase of about 10 s. The photophobic reaction time has been found to be about the same length of time. 2. The action spectra of both externally and internally measured light-induced potential changes correspond with the photophobic action spectrum, indicating the participation of the main photosynthetic pigments of Phormidium, chlorophyll a and phycobilins. A hypothesis is being discussed according to which sensory transduction between photoreceptor and motor apparatus of the cell is mediated by light-induced electrical potential changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00407931
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  • 5
    Electronic Resource
    Electronic Resource
    Photodynamically induced chemoresponses of the colorless flagellate, Astasia longa, in the presence of riboflavin (1985)
    Springer
    Archives of microbiology 142 (1985), S. 397-402 
    Details
    ISSN: 1432-072X
    Keywords: Astasia longa ; Chemoaccumulation ; Chemotaxis ; Flagellates ; Hydrogen peroxide ; Phobic response ; Riboflavin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the presence of the photosensitizer riboflavin, Astasia accumulates in illuminated fields at high fluence rates. The quenchers of riboflavin excited states, NaN3 and KI, abolish the photodynamic effect of riboflavin. Crocetin, a 1O2 quencher, does not influence the photodynamic action of riboflavin while 1,4-benzoquinone very strongly depresses its effect. This indicates a type I pathway forming H2O2 as a photoproduct. The photodynamic effect is abolished by the addition of 10-5 M catalase which breaks down H2O2. Astasia shows chemoaccumulations around the opening of a capillary filled either with riboflavin (under high intensity irradiation) or H2O2 which proves the hypothesis that the photobehavioral response in the presence of riboflavin is based on a chemoresponse toward H2O2, produced when the dye is irradiated. The accumulation around the capillary opening is not due to a direct chemotactic movement of cells but rather to a chemophobic response which prevents the cells from swimming away from the chemoattractant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00491911
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of inhibitors on photomovement in desmids (1981)
    Springer
    Archives of microbiology 129 (1981), S. 168-172 
    Details
    ISSN: 1432-072X
    Keywords: Desmids ; Inhibitors ; Microvideography ; Photokinesis ; Photophobic response ; Photosynthetic electron transport ; Phototaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of the inhibitors of the photosynthetic electron transport chain, 3-(3′,4′-dichlorophenyl) 1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), on the three phtoomovement responses known in the desmid Cosmarium cucumis have been studied. Both inhibitors block photokinesis very effectively in their respective specific concentration range. Most of the impairment of phototaxis and the photophobic response observed in population techniques seems to be due to a reduced motility of the cells, since microvideographic analysis of the cell movement indicated that the inhibitors do not affect the phobic response at all and that there is only partial inhibition of phototaxis. Both the fraction of motile cells and the duration of motility periods are affected by the inhibitors. The results demonstrate that, though all three photoresponses are mediated by chlorophyll acting as photoreceptor, at least the phobic response is independent of the photosynthetic electron transport chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00455356
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of UV-B on motility and photobehavior in the green flagellate, Euglena gracilis (1985)
    Springer
    Archives of microbiology 141 (1985), S. 159-163 
    Details
    ISSN: 1432-072X
    Keywords: Absorption ; Eulena gracilis ; Flagellate ; Fluorescence ; Motility ; Phobic response ; Photomovement ; Phototaxis ; UV-B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract UV-B inhibits the motility of the green flagellate, Euglena gracilis, at fluences rates higher than those expected to occur in the natural sunlight even when the stratospheric ozone layer is partially reduced by manmade pollutants. The phototactic orientation of the cells, however, is drastically impaired by only slightly enhanced levels of UV-B irradiation. Since only negative phototaxis (movement away from a strong light source) is impaired while positive phototaxis (movement toward a weak light source) is not, the delicate balance by which the organisms adjust their position in their habitat is disturbed. Under these conditions the cells are unable to retreat from hazardous levels of radiation and are eventually killed not by the UV-B irradiation but by photobleaching of their photosynthetic pigments in the strong daylight at the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00423278
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  • 8
    Electronic Resource
    Electronic Resource
    Gated ion fluxes involved in photophobic responses of the blue-green alga, Phormidium uncinatum (1982)
    Springer
    Archives of microbiology 131 (1982), S. 77-80 
    Details
    ISSN: 1432-072X
    Keywords: Amplification ; Blue-green algae ; Cations ; Gating channels ; Ionophores ; Phobic response ; Phormidium uncinatum ; Photomovement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sensory transduction chain of photophobic responses in the blue-green alga, Phormidium uncinatum seems to involve a gating cation transport through membrane bound ion channels which provides an effective amplification. The calcium conducting ionophore A23187 inhibits the photophobic response totally and induces frequent reversals which resemble phobic responses but occur without any light stimulation. This indicates that the electrogenic ion conductance may depend on a gradient of divalent cations, esp. calcium. The calcium conductance during a photophobic response is further confirmed by the inhibitory effect of ruthenium red and lanthanum, blockers of the electrogenic calcium transport. In the case of lanthanum this inhibition is found at a concentration at which neither the number of motile filaments nor the average speed of movement is impaired. Incorporation of ionophores for monovalent cations (gramicidin and valinomycin) only partially impairs the response. Similarly, inhibition of the Na+/K+ pump by ouabain is less effective. Thus, the existence of a countercurrent of monovalent cations during the response, which has been described for e.g. ciliates, is yet obscure in blue-green algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00451502
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  • 9
    Electronic Resource
    Electronic Resource
    Further evidence for the electron pool hypothesis (1976)
    Springer
    Archives of microbiology 110 (1976), S. 301-303 
    Details
    ISSN: 1432-072X
    Keywords: Blue-green algae ; Electron pool hypothesis ; Photophobic reaction ; Photosystems ; Phormidium uncinatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In continuation of experiments with photo-system II inhibitors [3-(3,4-dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6-isopropylbenzoquinone] the effect of photosystem I inhibitors was studied. 1. Neither the plastocyanin inhibitor, potassium cyanide, nor the ferredoxin antagonist, disalicyliden propandiamin, markedly affected those phobic reactions which are mediated by the electron transport via photosystem II into the electron pool. 2. On the other hand those phobic reactions, which are triggered by an increased flow of electrons out of the pool, are specifically inhibited by both substances. These results are regarded as further evidence that there is only one electron pool, the level of which triggers photophobic reactions and is located in the linear electron transport chain near photosystem II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690242
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  • 10
    Electronic Resource
    Electronic Resource
    Evidence of electrical potential changes in photophobically reacting blue-green algae (1978)
    Springer
    Archives of microbiology 118 (1978), S. 115-119 
    Details
    ISSN: 1432-072X
    Keywords: Blue-green algae ; Light-induced potential changes ; Phormidium uncinatum ; Photophobic response ; Sensory transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The correlation between photophobic responses and light-induced electric potential changes has been studied in the blue-green alga Phormidium uncinatum. 1. The photophobic reaction time depends on both length of preillumination and presentation time of stimulus. Under optimal conditions a reaction time of about 10 s has been determined. 2. Light-induced potential changes can be measured by means of external electrodes with a small gap between them bridged by a population of perpendicularly oriented trichomes. These potential changes follow a light-dark cycle with a lag phase of about 10 s. 3. The amplitude of these light-induced potential changes increases with light intensity until it reaches a saturation value of about 12 mV at 10000 lx. The action spectrum resembles the photophobic action spectrum with peaks in the absorption region of C-phycoerythrin and chlorophyll a. The significance of light-induced potential changes as a means of sensory transduction for photophobic responses in blue-green algae is being discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00406083
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