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  • 1
    Electronic Resource
    Electronic Resource
    Association of α-amylase and the R1 protein with starch granules precedes the initiation of net starch degradation in turions of Spirodela polyrhiza (2002)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 114 (2002), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In turions of Spirodela polyrhiza (L.) Schleiden, net degradation of storage starch is controlled by a special low fluence response of phytochrome requiring illumination for several days. This light effect has been used to study protein–starch interactions that occur prior to and during net degradation of starch. Following various pretreatments on S. polyrhiza turions, native starch granules were isolated and two fractions of starch-related proteins were distinguished: proteins enclosed within the starch particles (starch-internalized proteins) and those attached to the surface (starch-associated proteins). The pattern of starch-associated proteins as resolved by SDS-PAGE was more complex than that of starch-internalized proteins and varied depending upon the pretreatment of the turions. Two starch associated proteins were identified immunochemically as α-amylase (EC 3.2.1.1) and the R1 protein (Lorberth et al. (1998) Nature Biotechnology 16: 473–477). Dark-pretreatment of non-dormant turions does not induce starch net degradation. Under these conditions, α-amylase and R1 were bound to the surface of the starch granules. Continuous illumination with red light induces a rapid degradation of starch. Within the first 24 h of illumination the level of starch-associated α-amylase transiently increased and subsequently decreased rapidly. Similarly, the amount of the starch-associated R1 also decreased during illumination. The dissociation of both α-amylase and R1 from the starch granules preceded the decrease in starch content. However, binding of the two proteins to starch granules remained unchanged when the turions did not perform net starch degradation (as observed during continuous darkness, orthophosphate deficiency, or dormancy of the turions). Thus, during net starch degradation, so far unidentified changes are postulated to occur at the surface of the starch particles that are relevant for protein binding. This conclusion was supported by in vitro studies in which the binding of purified β-amylase (EC 3.2.1.2) to starch granules isolated from turions following various pretreatments was monitored. The enzyme did bind to starch granules prepared from dark-stored turions (in which starch degradation had not been initiated), but not to those isolated from illuminated (starch degrading) turions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2002.1140102.x
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of transcript level and nitrite reductase activity by phytochrome and nitrate in turions of Spirodela polyrhiza (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 93 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Control by light and nitrate of the appearance of nitrite reductase (NIR; EC 1.7.7.1) activity was investigated in turions of Spirodela polyrhiza during the pre-germination period to establish the nature of the coaction between these factors. A cDNA clone coding for tobacco NIR was available as a probe. In the period immediately after transfer from after-ripening conditions (5°C. darkness) to germination conditions (25°C; phase 1, from 0 to 72 h after start of the experiments) a nitrate-dependent increase in NIR activity was observed, presumably because of the temperature shift. During this phase light had no effect on the nitrate-dependent increase in NIR activity. In contrast, after a pre-treatment of 72 h in darkness at 25°C following cold afterripening responsiveness to phytochrome appeared, with light inducing a nitrate-dependent increase in NIR activity (phase II, from 72 to 120 h after start of the experiments). Application of nitrate (10 mM) in phase II also resulted in an increase of NIR activity in light or darkness although highest NIR activities were observed in the presence of light. Ammonium did not affect the appearance of NIR activity. In all experiments, a single isoform of NIR was detectable in both phases. It was concluded that the mode of coaction between light (via phytochrome) and nitrate is different in phase I and phase II and depends on the developmental state of the plant organs. Furthermore, the response patterns of nitrate reductase and NIR activities to both factors is so similar in turions that co-regulation of both enzymes can be assumed, as found previously in tobacco seedlings. Northern blot analyses revealed a low NIR transcript level in the absence of nitrate in darkness during phase II. Both light and nitrate alone were sufficient to stimulate the NIR mRNA steady state level and the highest transcript level was detectable in the presence of both stimulators. This demonstrates a synergistic effect of both factors on steady state NIR transcript level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb02228.x
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  • 3
    Electronic Resource
    Electronic Resource
    Photokinetic and photophysical parameters of the blue light induced phototransformation of phytochrome in the presence of flavin (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 63 (1985), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Flavin mononucleotide (FMN) transfers its excitation energy to phytochrome Pr with a rate constant 〈8.7 × 1011 I mol-1 s-1. This reaction is not specific for Pr. the transfer to the phytochrome Pfr proceeds with ?5.8 × 1011 1 mol-1 s-1. These rate constants are lower limits because the complex-formation constants are unknown. Assuming a horsier energy transfer a greater complex-formation constant, as well as a greater orientation factor or a smaller distance in the complex FMN-Pfr than in FMN-Pr would be the possible reason for the difference between the rate constants.It is shown that the “flavin effect” can only be of physiological relevance if the local phytochrome concentration does not reach the millimolar range at the same place Under these conditions the reaction Pr Pfr proceeds more effectively, but the reaction Pr Pfr less effectively than in the absence of the donor FMN. which gives rise to a shift of the equilibrium in favour of Pfr.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1985.tb04262.x
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  • 4
    Electronic Resource
    Electronic Resource
    Ion antagonism in phytochrome-mediated calcium-dependent germination of turions of Spirodela polyrhiza (L.) Schleiden (1999)
    Springer
    Planta 208 (1999), S. 583-587 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Calcium ; Germination ; Phytochrome ; Signal transduction ; Spirodela (germination) ; Turion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The light-dependent germination response of turions (resting fronds) is mediated by phytochrome and requires the presence of Ca2+ in the medium (K.-J. Appenroth and H. Augsten, 1990, Photochem. Photobiol. 52: 61–65). The Ca2+ requirement of germination is apparent only in the presence of exogenous Mg2+. A competitive ion antagonism was demonstrated between Ca2+ and Mg2+ in this physiological response; Mg2+ could also be replaced by Ba2+ or Sr2+. Without exog-enous Mg2+, a Ca2+ concentration as low as 0.9 μM fulfilled the Ca2+ requirement. This type of ion antagonism resembled the competitive Ca/Mg interaction reported previously for calcium-binding proteins. The physiological response was blocked by inhibitors of Ca2+ uptake (verapamil, La3+). It was concluded that uptake of Ca2+ from the external medium is an essential step in the phytochrome-mediated germination of turions. The results are in agreement with the assumption that the uptake of Ca2+ is blocked at the side of entry by other alkaline earth ions. Treatment of turions with Mg2+ (1 mM) for 24 h at varying times after the red light pulse in otherwise virtually Ca2+-free KNO3 solution resulted in a response similar to a Ca2+ step-down treatment. This is in agreement with the assumption that the Ca2+- and the Mg2+-sensitive periods coincide. The ion interaction described here represents the first photophysiological example in plants of an antagonistic effect between Ca2+ and Mg2+ similar to that which occurs in vitro with calmodulin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050596
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  • 5
    Electronic Resource
    Electronic Resource
    Wasserlinsen und ihre Nutzung (1996)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 26 (1996), S. 187-195 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Die Wasserlinsengewächse (Lemnaceae sind eine taxonomisch und ökologisch isoliert stehende Gruppe einkeimblättriger Pfanzen. Sie sind frei beweglich und schwimmen auf der Wasseroberfläche oder leben untergetaucht. Sie besitzen eine weltweite Verbreitung, wenn man von extremen Zonen wie Wüsten (zu trocken) und arktischen Gebieten (zu kalt) absieht (Abbildungen 1 und 2). Ihre Vermehrung erfolgt nicht oder nur selten über Samen, sondern meistens vegetativ durch Bildung von Tochterpflanzen, die von den Mutterpflanzen abgegliedert werden (Abbildung 3). Die Blütenstände sind stark vereinfacht. Auch ihr vegetativer Bau ist erheblich reduziert. Der Vegetationskörper ist nicht in Sproßachse und Blätter differenziert, sondern besteht aus blattartigen, zusammenhängenden Gliedern (Fronds). Einige Vertreter verfügen über nur eine Wurzel, andere sind wurzellos. Zu den Lemnaceen gehören die kleinsten Blütenpflanzen überhaupt mit einer Länge beziehungsweise mit einem Durchmesser von weniger als einem Millimeter (Wolffia angusta und Wolffia globosa) [10]. Bei den einheimischen Lemnaceen liegt das Größenspektrum zwischen 10-15 mm für Spirodela polyrrbiza und etwa 1 mm für Wolffia arrhiza.Trotz oder gerade wegen dieser Besonderheiten sind die Lemnaceen vielseitig verwendbar. Zunehmende Bedeutung erlangen sie bei der Biomasse- und Proteinproduktion, bei der Abfallbeseitigung und bei der Erzeugung von Bioenergie. Auch bei der Gewässerbeurteilung, der Gewässer- und Abwasserreinigung und im Rahmen der Bioindikation haben sie sich bewährt. Ferner wurden sie als Testsysteme zur Erfassung und Bestimmung phytoaktiver Substanzen (zum Beispiel Wachstumsregulatoren und Herbizide) sowie von toxisch wirkenden Stoffen eingesetzt. Schließlich ist es möglich, sie in Bioreaktoren zur kontinuierlichen Katalyse von Stoffwandlungsprozessen oder als Trenn- und Trägermaterial zu verwenden.In den folgenden Ausführungen soll auf einige Anwendungsgebiete etwas näher eingegangen werden.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19960260311
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  • 6
    Electronic Resource
    Electronic Resource
    Die Vielwurzelige Teichlinse. Ohne Stickstoff „geht nichts“ (1993)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 23 (1993), S. 102-107 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Es wird immer deutlicher, daß die Überlastung der Ökosysteme mit Stickstoff (Nitrat und Ammonium) eine wesentliche Ursache fur die beobachtbaren ökologischen Schäden darstellt [I]. Dieser Stickstoff ist anthropogener Herkunft (beispielsweise aus industriellen Verbrennungsanlagen, Autoverkehr, landwirtschaftlicher Tierhaltung) und gelangt über Luftschichten unterschiedlicher Hohe in alle Gebiete Deutschlands. Selbst Reinluftgebiete sind von den Stickstoffdepositionen nicht mehr verschont: In nahezu allen Wäldern ist der Stickstoffeintrag inzwischen größer als die Menge, die selbst unter optimalen Bedingungen assimiliert werden kann [2,3,4].Für Pflanzen hat sich mit dem Überangebot an Nitrat und Ammonium die ursprüngliche Mangelsituation umgekehrt. Im Verlauf der Evolution war Stickstoff stets „ein kritisches Element der Biosphäre“ [5], und es galt, den Stickstoffmangelbedingungen durch evolutionäre Anpassung zu begegnen. Die Überlastung der Ökosysteme heute mit Stickstoff ist nicht nur auf Waldflächen zu beobachten; auch aquatische Ökosysteme sind betroffen [6]. Wir untersuchten deshalb den Einfluß von Nitrat und Ammonium auf Wachstum und Entwicklung von aquatischen Blütenpflanzen. Dabei haben sich Wasserlinsen (Lemnaceae) als Testobjekte bewährt. Sie sind weltweit verbreitet und meiden lediglich zu trockene oder zu kalte Gebiete [7]. Zahlreiche Eigenschaften machen die Wasserlinsen für Untersuchungen im Labor besonders geeignet [8]: Sie können in vitro kultiviert werden, der Platzbedarf ist ge ring, und durch eine hohe Vermehrungs bzw. Wachstumsrate werden innerhalb kurzer Zeit Klone gebildet, so daß genetisch identische Pflanzen für die Untersuchungen zur Verfügung stehen.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19930230209
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