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  • 1
    Electronic Resource
    Electronic Resource
    Early quantitative method for measuring germination in non-green spores of Dryopteris paleacea using an epifluorescence-microscope technique (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 73 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A method is described to determine germination by blue-light excited red fluorescence in the positively photoblastic spores of Dryopteris paleacea Sw. This fluorescence is due to chlorophyll as evidenced from 1) a fluorescence-emission spectrum in vivo, where a bright fluorescence around 675 nm is obtained only in red light (R)-irradiated spores and 2) in vitro measurements with acetone extracts prepared from homogenized spores. Significant amounts of chlorophyll can be found only in R-treated spores; this chlorophyll exhibits an emission band around 668 nm, when irradiated with 430 nm light at 21°C.Compared to other criteria for germination, such as swelling of the cell, coat splitting, greening, and rhizoid formation, which require longer periods after induction for their expression, chlorophyll fluorescence can be used to quantify germination after two days. This result is confirmed by fluence-response curves for R-induced spore germination; the same relationship between applied R and germination is obtained by the evaluation with the epifluorescence method 2 days after the light treatment as compared with the evaluation with bright-field microscopy 5 days after the inducing R.Using this technique we show for the first time that Ca2+ contributes to the signaltransduction chain in phytochrome-mediated chlorophyll synthesis in spores of Dryopteris paleacea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb05433.x
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  • 2
    Electronic Resource
    Electronic Resource
    Motility and orientation of a dinoflagellate, Gymnodinium, impaired by solar and ultraviolet radiation (1993)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 102 (1993), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effects of solar and artificial ultraviolet radiation on the motility and orientation of the dinoflagellate Y-100 were studied. The cells show a weak photokinesis but a pronounced phototaxis which is consistently positive between 1 and 100 klx (= 4 mW m−2 to 400 mW m−2); the precision of orientation increases with the fluence rate. Unfiltered solar radiation as well as artificial ultraviolet radiation reduce the percentage of motile cells increasingly with exposure time but the velocity of the still motile cells is less affected. Unirradiated control cells show a negative gravitaxis. After short exposure to solar or artificial ultraviolet radiation the precision of gravitaxis decreases and after prolonged exposure the cells start to actively move downward in the water column (positive gravitaxis). Phototaxis is also strongly impaired by ultraviolet radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1993.tb05807.x
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  • 3
    Electronic Resource
    Electronic Resource
    Germination in spores of Dryopteris filix-mas: Regulation of rhizoid elongation as a second phytochrome-mediated response (1996)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Spore germination in Dryopteris filix-mas occurs via a cascade of cellular responses, and chlorophyll formation, mitosis or rhizoid elongation are commonly used as parameters to determine spore germination. Detailed investigations of these parameters led to the hypothesis that they are regulated by different, independent phytochrome-mediated responses. This concept could be confirmed, as is described in this paper which demonstrates that perception of light via phytochrome occurs within two different phases separated in time. Presence of the far-red absorbing phytochrome form, Pfr, for 36 h, induces chlorophyll formation and the first unequal cell division, by which a rhizoid initial and a protonemal initial are formed (first phytochrome-mediated response). However, rhizoid elongation requires a second period of Pfr, presence (second phytochrome-mediated response). There is a clear temporal distinction between the first and the second phytochrome-mediated response with respect to the coupling of Pfr to the transduction chain; Pfr is unable to induce rhizoid growth until 60 h after the start of the first red irradiation. The effectivity of Pfr for inducing the second response shows an optimum at ca 96 h after the beginning of the presence of Pfr; thereafter, it declines slowly. The fluence-response relationship and the presence of red/far-red reversibility demonstrate that rhizoid elongation is a low-fluence response mediated by phytochrome and is independent of the first phytochrome response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1996.980223.x
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  • 4
    Electronic Resource
    Electronic Resource
    Phototransformation of oat phytochrome with millisecond and submillisecond flashes: The level of the photostationary Pfr/Ptot ratio is modified by photoreversible intermediates (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 65 (1985), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Photoconversion of the red-absorbing form of phytochrome (Pr) to the far-red-absorbing form of phytochrome (Pfr) and vice versa has been measured spectrophotometrically at 10°C in immobilized and soluble phytochrome (118 kdalton), prepared from 5-day-old etiolated oat seedlings (Avena saliva L. cv. Sol II). The photostationary equilibrium φ= PfrPtot (with Ptot= total amount of phytochrome Pr+ Pfr) for red light depends on whether it is established by repetitive pulses (≥ 5 s) or by repetitive flashes (≥ 4 ms). In the wavelength region around 660 nm, a lower φ is reached with flashes as compared to that with pulses. This difference becomes negligible if the wavelength is shortened to the 600 nm region, and it also disappears if the fluence of each individual flash is reduced. In contrast, in long-wavelength red light and short-wavelength far-red light, a higher φ is reached with flashes than with pulses.We relate the differences in φ for flash and pulse irradiation to photochromic systems between Pr and photoreversible intermediates in the phototransformation pathway Pr→ Pfr. Thus, light absorption by phytochrome intermediates can be limiting for the quantitative relationship between light signal and Pfr formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1985.tb08683.x
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  • 5
    Electronic Resource
    Electronic Resource
    Polar distribution of annexin-like proteins during phytochrome-mediated initiation and growth of rhizoids in the ferns Dryopteris and Anemia (1995)
    Springer
    Planta 197 (1995), S. 376-384 
    Details
    ISSN: 1432-2048
    Keywords: Anemia ; Annexin-like proteins ; Dryopteris ; Rhizoid development ; Tip growth (vesicle-mediated)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although the calcium requirement of phytochrome-mediated fern spore germination and early rhizoid growth is well established, the calcium-binding proteins that serve as transducers for these responses are not known. Here we report the presence of annexin-like proteins in germinating spores of Dryopteris filix-mas (L.) Schott and Anemia phyllitidis (L.) Sw. and evidence that they may be important participants in early photomorphogenic changes in gametophytes. Immunolocalization and immunoblot assays of these proteins were carried out using polyclonal antibodies raised either against a 35-kDa annexin-like protein from pea or against anchorin CII from chicken. Western-blot analysis showed that crude protein extracts obtained from both species after red-light treatment contained two cross-reactive protein bands with molecular weights around 70 kDa. These proteins were annexin-like in that they bound to a phosphatidylserine affinity column in a calcium-dependent fashion. Using this column, two protein bands around 70 kDa, i.e. 67 and 73 kDa, were partially purified together with proteins at 36 kDa and a doublet at 54 kDa. Proteins of these latter molecular weights are suggested to be members of the annexin family, but no cross-reactivity could be found between these and the two antibodies used in our investigations. Immunodetectable levels of these proteins were observed only after light-mediated induction of spore germination. Imaging of the immuno-localization patterns observed with both antibodies showed that the annexin-like proteins are concentrated at the extreme tips of the rhizoids in D. filix-mas and A. phyllitidis during rhizoid initiation and all stages of elongation. We suggest that these proteins may play a major role in the tip-oriented exocytosis events that are critical for the initiation and growth of fern rhizoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202660
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  • 6
    Electronic Resource
    Electronic Resource
    Phytochrome-dependent modulation and re-induction of growth of the first rhizoid in Dryopteris paleacea Sw (1999)
    Springer
    Planta 208 (1999), S. 98-106 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Dryopteris ; Gametophyte ; Intercellular signaling ; Phytochrome ; Rhizoid ; Tip growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Phytochrome-dependent growth in Dryopteris paleacea Sw. was investigated in young, developing gametophytes with respect to formation and differentiation of rhizoids. Under continuous red light (Rc), the first rhizoids grew synchronously by tip elongation at a constant rate of 240 μm · d−1 until formation and outgrowth of the second rhizoid. Cessation of growth of the first rhizoids and outgrowth of the second rhizoids showed a correlation in time assumed to be mediated by intercellular signaling. The first rhizoids showed two modes of response to actinic irradiations: (i) modulation of rhizoid growth, and (ii) re-induction of growth in non-growing rhizoids. In the former, the promotory effect of actinic irradiations on rhizoids pre-cultured under Rc determined both the time for which rhizoids continued to grow after transfer into darkness and the final rhizoid length. In the latter, re-induced growth was studied using non-growing rhizoids which were obtained after irradiation with a far-red light (FR) pulse at the end of the pre-culture in Rc and transfer into darkness for 3 d to stop growth. Re-induction of growth occurred with a lag phase of 36 to 48 h after formation of the FR-absorbing form of phytochrome (Pfr) by a red light (R) pulse. From the incomplete R/FR reversibility it is evident that, here, coupling of Pfr to signal transduction is possible within minutes. Re-induction of growth possesses the advantage that the effect of actinic irradiations can be studied as an all-or-none response at the level of single gametophytes in future experiments. The present results clearly indicate that the developmental stage of the whole gametophyte, i.e. temporal and spatial patterns undergone during development, affects the regulation of rhizoid growth by the external factor light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050539
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Phytochromgesteuerte Farnsporenkeimung (1995)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 25 (1995), S. 178-184 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Im Entwicklungszyklus der Pflanzen treten verschiedene Formen von Fortpflanzungs und Verbreitungseinheiten, wie Pollen, Samen oder Sporen, auf. Sie dienen neben der Vermehrung und Ausbreitung in vielen Fällen auch der Überdauerung ungünstiger Lebensbedingungen. Demgemäß wird ihre Keimung durch eine Vielzahl von Außenfaktoren auf sehr mannigfaltige Weise beeinflußt. Die komplexen Vorgänge, die dabei ablaufen, sind Gegenstand intensiver Forschung, nicht zuletzt deshalb, weil gerade die Samenkeimung bei Nutzpflanzen für die landwirtschaftliche Produktion von großer Bedeutung ist. Dagegen sind Farne in wirtschaftlicher Hinsicht zwar nur von geringem Interesse, ihre Sporen bieten aber aufgrund ihrer Einzelligkeit im Vergleich zu den vielzelligen, komplex gebauten Samen erhebliche experimentelle Vorteile für die Analyse der Keimungsinduktion: So beeinflußt die Variation verschiedener Versuchsparameter, wie die Versuchstemperatur oder die Zusammensetzung des Kulturmediums, die zu untersuchende Zelle direkt und ohne wesentliche zeitliche Verzögerung. Die Dokumentation des Keimungsprozesses ist durch direkte, mikroskopische Beobachtung der lebenden Zelle möglich. Außerdem müssen Wechselwirkungen zwischen verschiedenen Geweben bei den einzelligen Farnsporen nicht berücksichtigt werden, und man kann aufgrund der geringen Sporengröße von etwa 50 μm im Labor mit sehr großen Stichprobenumfängen arbeiten [5, 22].Bei unseren Ausführungen beschränken wir uns im folgenden auf die lichtinduzierte Keimung von Sporen der Gattung Dryopteris (Wurmfarn) [12]. Unser Interesse gilt der Charakterisierung des absorbierenden Pigmentsystems Phytochrom unter Berücksichtigung molekularbiologischer Fragestellungen sowie der Bedingungen, unter denen der Außenfaktor Licht perzipiert werden kann. Darüber hinaus untersuchen wir die modifizierende Wirkung weiterer Umweltfaktoren auf den lichtinduzierten Keimungsverlauf, der im folgenden durch eine Abfolge charakteristischer Differenzierungsschritte beschrieben wird.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19950250316
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