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  • 1
    Call number: 01-Ausbildungsl:674
    Keywords: Botanical microscopy / Technique ; Botany / Anatomy ; Plant cells and tissues
    Pages: xiii, 201 p. : ill.
    Edition: 10., überarb. und erw. Aufl.
    ISBN: 3-13-440310-2
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 112 (1977), S. 179-185 
    ISSN: 1432-072X
    Keywords: Movement ; Phototaxis ; Carbon dioxide tension ; pH ; Circadian rhythm ; Chlamydomonas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The effects of carbon dioxide, oxygen and pH on the inversion intensity of phototaxis of Chlamydomonas reinhardtii have been investigated. 2. With decreasing CO2 tension the inversion intensity is decreased. 3. The gassing with CO2 can be substituted by hydrogencarbonate only to a small extent (20%). On the other hand, the effect of decreasing CO2 tension can be prevented also only in part by adjusting the pH to about 6.5–7.0. Thus the effect of CO2 on the inversion intensity of phototaxis is obviously a compostite of a true CO2 effect and an effect of the concomitant pH change. 4. Oxygen has only a slight effect. In presence of oxygen (air) the phototactic reaction values are somewhat lower than in its absence. 5. Under certain conditions circadian rhythms seem to be initiated by changing oxygen as well as CO2 tensions. 6. Based on these results some contradictory results of older investigations are discussed.
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  • 3
    ISSN: 1432-072X
    Keywords: Photokinesis ; Red algae ; Porphyridium cruentum ; Action spectrum ; Photosynthesis ; Inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photokinesis of the red alga Porphyridium cruentum was studied with the aid of a population method. Because of the slow spreading velocity (0.35 μm/min) the duration of the experiments was 7 days in general. According to the white light illuminance-response curve the zero threshold of photokinesis lies below 10 lx and the optimum around 10,000 lx. With further increasing illuminance the photokinetic effect decreases, reaching zero at about 100,000 lx. The action spectrum indicates that the photokinetically active radiation is absorbed by photosynthetic pigments, namely the biliproteins B-phycoerythrin, R-phycocyanin and allo-phycocyanin, as well as by chlorophyl a, although the photokinetic effect of blue light is relatively low. From the action spectrum and the results of inhibitor experiments with DCMU, DBMIB and DSPD it is concluded that the photokinetic effect is due to an additional ATP supply from non-cyclic and/or pseudo-cyclic photophosphorylation to the motor apparatus.
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  • 4
    ISSN: 1432-072X
    Keywords: Anabaena variabilis ; Cyanobacteria ; Cyanophyceae ; Phototaxis ; Singlet oxygen ; Carotenoids ; Furan derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hypothesis has been proposed that in Anabaena variabilis the phototactic reaction sign is regulated by an unknown reaction sign reversal generator which is controlled by the intracellular level of singlet molecular oxygen (1O2). This hypothesis is supported by the following findings presented in this paper: Gassing with N2 and Ar shifts the phototactic transition point at which the positive reaction becomes negative to higher fluence rates. Surprisingly this is true also for gassing with molecular oxygen 3O2. Since 1O2 is produced in photosynthesis, the availability of external molecular oxygen seems not to be important. Apparently, a stream of any gas which is fast enough to remove 1O2 from the surface of the Anabaena trichomes decreases the internal 1O2 concentration and this way acts on the reaction sign reversal generator. Moreover, several carotenoids such as the water-soluble crocetin and preparations of solubilized β-carotene, canthaxanthine and the C30-ester ethyl-β-apo-8′-carotenoate shift the transition point of phototaxis to higher fluence rates by about one order of magnitude. Several tested furan derivatives, such as dimethylfuran, diphenylisobenzofuran, and furfuryl ethanol, are either cytotoxic or not water-soluble at the concentrations necessary for an effective 1O2 quenching. Based one these results a model of the phototactic reaction chain of A. variabilis is proposed.
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  • 5
    ISSN: 1432-072X
    Keywords: Phototaxis ; Red algae ; Porphyridium cruentum ; Action spectrum ; DCMU ; Iodide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phototaxis of the unicellular red alga Porphyridium cruentum was studied by staining the slime tracks of individual cells as well as with the aid of a population method. Because of the increased straightness of the movement the mean linear velocity of a unilaterally illuminated population exceeds considerably that of an only photokinetically stimulated one. In white light the phototactic reaction is saturated already at 100 lx. The zero threshold lies at about 1 lx. Spectral sensitivity curves of phototaxis obtained at high photon fluence rates (〉=10−11 mol cm−2 s−1) display two main peaks which shift against each other at intermediate irradiances and, finally, form a single maximum in the blue range (443 nm) at low photon fluence rates (10−12 and 10−13 mol cm−2 s−1). Photon fluence rate-response curves reveal that supraoptimal irradiances decrease the phototactic reaction, especially in the range of the highest sensitivity of the cells. The action spectrum of phototaxis was calculated on the basis of the photon fluence rate-response curves. It shows a maximum at 443 nm and shoulder at 416 nm and between 467 and 477 nm. Wavelengths longer than 540 nm are phototactically inactive even at very high irradiances (25 W m−2). Thus, this is the first phototactic action spectrum of a biliprotein-containing organism which does not indicate the participation of biliproteins in the absorption of phototactically active light. DCMU and potassium iodide have no specific effects on phototaxis.
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  • 6
    ISSN: 1432-072X
    Keywords: Movement ; Phototaxis ; Action spectrum ; Blue-green algae ; Cyanophyceae ; Anabaena variabilis ; Inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phototaxis of the blue-green alga Anabaena variabilis was studied using both population method and observation of single trichomes by microscope. The trichomes react positively at low and negatively at high illuminance. The inversion point lies at about 1000 1x. The action spectrum of positive phototaxis indicates that the photosynthetic pigments chlorophyll a, C-phycocyanin and allo-phycocyanin are involved in the absorption of the active light. The same range of wavelengths is active in negative phototaxis, but in addition, wavelengths between 500 and 560 nm and between 700 and 750 nm are also effective. Obviously pigments of unknown chemical nature are sharing in light absorption. Two alternatives are discussed. Since inhibitors of photosynthesis such as DCMU and DBMIB do not affect phototactic orientation, a direct coupling of phototaxis with photosynthesis can be excluded.
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  • 7
    ISSN: 1432-072X
    Keywords: Movement ; Phototaxis ; Photokinesis ; Circadian Rhythm ; Chlamydomonas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. A fully automated phototaxis monitoring device is described for measuring photo-topatactic responses of flagellated organisms. 2. Photokinesis can be demonstrated in Chlamydomonas cells only after a dark period of about 72 hrs. 3. Pre-darkening of a few hours duration raises the phototactic disposition, whereas pre-illumination has no significant effect. 4. Circadian rhythms can be initiated by only one period of darkness or lower light intensity, whereas a period of higher intensity does not induce rhythms. The period length of the circadian rhythms is about 24 hrs.
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  • 8
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung 1. Es wird eine Apparatur zur quantitativen Messung phototopotaktischer Reaktionen bescherieben, die direkt mit einer homokontinuierlichen Kulturanlage gekoppelt ist. 2. Die Analyse von Zellzahl, packed cell volume, Pigmentgehalt und phototaktischem Reaktionsverhalten hat gezeigt, daß das auf diese Weise angezogene Versuchsmaterial homogen und in seinem Reaktionsverhalten weitgehend konstant ist. 3. Chlamydomonas reinhardii reagiert im gesamten untersuchten Bereich zwichen 10 und 100 000 Lux positiv photo-topotaktisch. Hierbei tritt stets eine negative Anfangsreaktion auf, die nach einigen Minuten in eine positive Reaktion übergeht. 4. Das Aktionsspektrum der Photo-topotaxis zeigt eine Wirksamkeit der Strahlung zwischen etwa 350 und 550 nm mit einem Maximum bei 503 mm und einem Nebenmaximum bei 443 nm. Demnach kommen als Photoreceptoren nur gelbe Pigmente in Frage, doch läßt sich wegen der geringen Differenziertheit des Spektrums nicht entscheiden, ob es sich um Carotinoide oder Flavine handelt. 5. Die spektrale Empfindlichkeit der negativen Anfangsreaktion entspricht etwa der der positiven photo-topotaktischen Reaktion. Dies berechtigt zu dem Schluß, daß es sich auch bei dieser Anfangsreaktion um eine echte Phototaxis handelt. Die Ursachen der Änderung des Reaktionssinnes sind nicht bekannt, doch könnte sie durch Änderungen in der CO2-Spannung des Mediums während der ersten Minuten des Versuches verursacht sein.
    Notes: Summary 1. An apparatus for quantitative measuring and recording the phototopotatic response of flagellated organisms, which is directly coupled with a homocontinuous culture, is described. 2. Periodical controls of cell number, packed cell volume, pigment content and phototactic responses revealed that the culture is in fact homogeneous, in so far as cell number, packed cell volume and pigment content are satisfactorily constant, and changes in the phototactic behaviour due to changes of the so called “phototactic disposition” are largely eliminated this way. 3. Chlamydomonas reinhardii displays positive phototopotactic reactions in white light between 10 and 100 000 lux. However, in all experiments initial negative responses have been observed. 4. The action spectrum shows that only near UV and visible radiation of shorter wavelengths up to 550 nm is photo-topotactically active. The main maximum lies at 503 nm, a smaller second one at 443 nm. However, the action spectrum does not allow to decide whether flavins or carotenoids are the photoreceptors of phototopotaxis. 5. The initial negative response shows a similar spectral sensitivity as the positive phototaxis. Therefore, it is probably due to the same reaction mechanism. According to recent investigations carried out by Marbach and Mayer (1970) it could be due to changes in the phototactic sensitivity caused by changes in the CO2-concentration of the medium during the first minutes of the experiment.
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  • 9
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung 1. Es wurde das photokinetische Reaktionsverhalten von Anabaena variabilis und Phormidium ambiguum vergleichend untersucht. 2. Im Weißlicht zeigen die beiden Arten keine auffälligen Unterschiede im Reaktionsverhalten, mit der einen Ausnahme, daß die Nullschwelle im Falle von Anabaena bei 10 Lux, im Falle von Phormidium dagegen bei 0,02 Lux liegt. 3. Die photokinetischen Aktionsspektren beider Arten sind grundverschieden. Während bei Ph. ambiguum nur blaues und rotes Licht, entsprechend seiner Absorption durch Chlorophyll a, wirksam ist, stimmt bei A. variabilis das Maximum der photokinetischen Wirksamkeit mit dem Absorptionsmaximum des C-Phycocyanins überein. Das durch Chlorophyll a absorbierte Rotlicht ist ebenfalls wirksam, doch ist im Aktionsspektrum in diesem Bereich weder ein Nebenmaximum noch eine Schulter zu erkennen. Blaulicht ist völlig unwirksam. 4. Die in vivo-Absorptionsspektren beider Arten sind fast identisch, so daß Unterschiede im Pigmentgehalt nicht die Ursache für die Verschiedenheit der photokinetischen Aktionsspektren sein können. 5. Bei A. variabilis wird die Photokinesis schon durch 10-7 bis 10-6 M DCMU deutlich gehemmt, während bei Ph. ambiguum erst Konzentrationen über 5·10-5M wirksam sind. Desaspidin hemmt die Photokinesis bei beiden Arten, doch scheint seine Wirkung nicht sehr spezifisch zu sein. Gegen DBMIB ist die Photokinesis von Anabaena empfindlicher als die von Phormidium. 6. Durch den Zusatz von 2·10-4 M Kaliumferrocyanid wird die Geschwindigkeit der Bewegung im Licht, nicht aber im Dunkeln, bei Ph. ambiguum erhöht, während bei A. variabilis kein Effekt zu beobachten ist. 7. Aus diesen Ergebnissen wird der Schluß gezogen, daß bei Ph. ambiguum, wie auch bei anderen Phormidium-Arten, der photokinetische Effekt das Ergebnis einer zusätzlichen ATP-Zufuhr aus der cyclischen Photophosphorylierung mit Photosystem I ist. Dagegen ist bei A. variabilis die Beschleunigung der Bewegung durch Licht offenbar auf eine Energiezufuhr aus der pseudocyclischen Photophosphorylierung zurückzuführen, an der beide Photosysteme beteiligt sind.
    Notes: Summary 1. The photokinetic behaviour of Anabaena variabilis has been investigated and compared with that one of Phormidium ambiguum. 2. In white light, no striking differences in the photokinetic behaviour have been observed, with the exception that the zero threshold lies at 10 lux in Anabaena and at about 0.02 lux in Phormidium. 3. The photokinetic action spectra of both the species are quite different. While in Ph. ambiguum blue and red light is active, according to its absorption by chlorophyll a, in A. variabilis the maximum of photokinetic activity coincides with the absorption maximum of C-phycocyanin. Red light absorbed by chlorophyll a is also effective, but no distinct peak or shoulder is detectable in the action spectrum at these wavelengths. Blue light has no effect at all. 4. The in vivo absorption spectra of both the species are almost identical. Thus, the differences in the spectral photokinetic sensitivity cannot be due to differences in the pigment content. 5. Photokinesis of A. variabilis is markedly inhibited by 10-7-10-6 M DCMU, while in Ph. ambiguum the DCMU concentration must exceed 5×10-5M. Desaspidin inhibits photokinesis in both the species, but the effect is obviously not a specific one. Furthermore, photokinesis of Anabaena is more sensitive to DBMIB than photokinesis of Phormidium. 6. The speed of movement in the light, but not in the dark, is increased by the addition of 2×10-4 M potassium ferrocyanide in Ph. ambiguum, while in A. variabilis no effect can be observed. 7. From these results it is concluded that in Ph. ambiguum, as in other Phormidium species, the photokinetic effect is the result of an additional ATP supply from cyclic photophosphorylation with photosystem I, while in A. variabilis the acceleration of movement by light is due to an energy supply from a phosphorylation process of the pseudocyclic type which is mediated by both the photosystems I and II.
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  • 10
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung 1. Das photo-phobotaktische Reaktionsverhalten einzelner Zellen einer Kultur von Navicula peregrina wurde mit Hilfe der Engelmannschen Lichtfallenmethode untersucht. Dabei zeigte sich, daß die Zellen beim Verlassen des Lichtfeldes verschieden tief in das dunkle Umfeld eintauchen, ehe sie umkehren. Am häufigsten, d.h. bei etwa 9% der Gesamtzahl, tauchten sie bis zu 65% der Zellänge in das dunkle Umfeld ein, doch kommen auch alle anderen Werte vor, allerdings um so weniger häufig, je weiter sie sich von dem 65%-Wert entfernen. 2. Die Reaktionszeit, d.h. die Zeit vom Überschreiten der Hell-Dunkel-Grenze bis zur Bewegungsumkehr, beträgt bei einer Beleuchtungsstärke von 1000 Lux im Durchschnitt 10±1 sec. 3. Mit Hilfe eines Spaltmikroskopes wurden Partialbelichtungen und Partialbeschattungen einzelner Zellen durchgeführt. 4. Bei der Partialbelichtung (1000 Lux) verschieden großer Abschnitte (10, 25, 50 und 75%) des Hinterendes verdunkelter Zellen zeigte sich überraschenderweise keine Beziehung zwischen der Größe der belichteten Fläche und der Reaktionszeit, deren Durchschnittswert ebenfalls 10±1 sec betrug. 5. Entsprechende Partialbeschattungen des Vorderendes belichteter Zellen ergaben den gleichen Wert. Demgegenüber beträgt der Zeitraum zwischen zwei autonomen Umkehrreaktionen bei 1000 Lux etwa 60 bis 70 sec. 6. Umgekehrt wird durch Belichtung (1000 Lux) des Vorderendes einer sich im Dunkeln bewegenden Diatomee die Zeit zwischen zwei Umkehrreaktionen auf 240 bis 260 sec, also etwa auf das Vierfache des autonomen Rhythmus, verlängert. Auch in diesem Falle spielt die Größe der belichteten Fläche keine Rolle. 7. Führt man Partialbelichtungen mit Lichtfeldern, deren Durchmesser 25% der Zellänge beträgt, in verschiedenen Bereichen der Zelle durch, so mißt man bei Belichtung der Zellmitte eine Reaktionszeit, die größenordnungsmäßig mit der Periode des autonomen Umkehrrhythmus übereinstimmt. Im übrigen ist die Reaktionszeit um so kürzer, je weiter das Lichtfeld nach hinten, und um so länger, je weiter es nach vorn verschoben wird. 8. Die Ergebnisse werden unter dem Aspekt der Lokalisation des Photoreceptors der photo-phobotaktischen Reaktion in der Zelle diskutiert.
    Notes: Summary 1. The photo-phobotactic behaviour of single cells of Navicula peregrina has been investigated with the aid of Engelmann's light trap method. At 1000 lx the cells react positively, i.e. they reverse the direction of movement if they undergo a decrease in light intensity passing the border between the light trap and the dark surrounding field. The size of the shaded area of the cells at the moment of the induced stop varies greatly. Most frequently, i.e. in 9% of the total number of cells investigated, the diatoms returned when the diameter of the darkened area was about 65% of the cell length, and the percentage was the less, the smaller or greater the darkened area was. 2. The average value of the reaction time, i.e. the time between the beginning of the darkening of the front pole and the resumption of movement in the opposite direction, was about 10 sec. 3. With the aid of a special microscope, in which the condenser is replaced by an achromatic objective, partial illumination and partial shading experiments in single cells have been carried out. 4. In the partial illumination experiments increasing areas (10, 25, 50, 75%) of the rear pole of a Navicula cell moving in the dark were exposed to 1000 lx by shifting the cells sidewards into the light field. Independent of the size of the irradiated part of the cell the average reaction time was 10±1 sec in all experiments. 5. The same reaction time has been measured, when increasing areas of the front pole of a cell moving in the light were shaded. Thus the reaction time is about a sixth of the period of the autonomous rhythm of forward and backward movement which amounts to 60–70 sec in Navicula peregrina at 1000 lx. 6. When increasing areas of the front pole of a cell moving in the dark were irradiated, the time between two returns is extended to 240–260 sec, while even in this case no correlations between the size of the irradiated area and the reaction time can be observed. This way it is possible to extend the periods of the autonomous rhythm and “draw” the cells following the light spot over a longer distance. 7. In another series of experiments light fields of a constant size, the diameter of which was 25% of the cell length, were projected onto different parts of the diatoms. If the middle of the cell was illuminated, the reaction time equaled about the period of the autonomous rhythm. The more the light field was shifted to the rear pole, the shorter was the reaction time, reaching 10 sec when only the rear pole was irradiated. Conversely, the reaction time was the longer the more the light field was shifted to the front pole. 8. The results are discussed in respect to the localisation of the photoreceptor molecules of photo-phobotaxis in the Navicula cell.
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