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  • 1
    Electronic Resource
    Electronic Resource
    In-vivo phytochrome control of in vitro transcription rates in isolated nuclei from oat seedlings (1984)
    Springer
    Planta 161 (1984), S. 444-450 
    Details
    ISSN: 1432-2048
    Keywords: Avena (phytochrome) ; Nucleus (transcription) ; Photoinduction (phytochrome) ; Phytochrome (transcription) ; Transcription (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transcription rate of isolated nuclei from oat seedlings was analysed by measuring the incorporation of radioactive label in trichloroacetic-acid-pelletable material. It was observed that this transcription rate depends on the light pretreatment of the plants: 7.5 h after a 5-min red or far-red light pulse maximum rates were found, but at this time far-red light induced only about half of the stimulation observed after a red light pulse. The far-red reversibility of the effect of the red light pulse indicates that phytochrome controls the capacity for transcription by isolated nuclei. Besides this slow reaction, phytochrome regulated the transcription rates in a very fast response when homogenates were irradiated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394576
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  • 2
    Electronic Resource
    Electronic Resource
    Phototropism of maize coleoptiles Influences of light gradients (1988)
    Springer
    Planta 176 (1988), S. 212-220 
    Details
    ISSN: 1432-2048
    Keywords: Blue-light receptor ; Coleoptile ; Phytochrome (light gradient) ; Phototropism (bluelight receptor) ; Zea (phototropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The lateral fluence-rate gradients in unilaterally irradiated maize (Zea mays L.) coleoptiles were calculated on the basis of the proportions of P fr (far-red-absorbing form of phytochrome) measured spectroscopically in transverse slices of the coleoptiles (top 1 cm). The results showed the occurrence of significant gradients that are wavelength-dependent. The gradient at 449 nm was steeper than those measured at 516, 534 and 551 nm, which were steeper than that measured at 665 nm. The ratios between the sides proximal and distal to the light source were, for example, 1:0.12 (449 nm), 1:0.23 (534 nm), and 1:0.28 (665 nm). Fluence-response curves for coleoptile phototropism (first positive curvature produced by less than 100 s unilateral irradiation) were measured at 449, 516, 534 and 551 nm. Comparison of the threshold fluences indicated that the responsiveness to 551 nm is about 104.8 less than that to 449 nm. Increasing wavelengths led to a decrease in maximal curvature, which correlated with the decrease of the fluence-rate ratios between the proximal and distal sides. Phototropic fluence-response curves were also measured using bilateral irradiation (449 nm). In one set of experiments, the fluence ratio was kept constant (either 1:1/2, 1:1/4 or 1:1/16) and the total fluence was varied, and in the other set the fluence applied to one side was kept constant and the fluence ratio was varied. A simple model based on the assumption that only one photoreaction occurs, and that the response is a function of the difference between the proximal and distal sides in the local photoreceptor action was tested. A fluence-response curve for this local photoreceptor action was calculated based on the fluence-rate ratio and the phototropic fluence-response curve measured for 449 nm. This curve was used, in conjunction with the measured fluence-rate ratios, as a basis for calculating phototropic fluence-response curves for other wavelengths and those for 449 nm obtained with bilateral irradiation. The calculated fluence-response curves showed excellent agreement with the experimental data. It is concluded that the threshold for maize coleoptile phototropism reflects the apparent photoconversion cross-section of the blue-light receptor whereas the maximal curvature depends on the steepness of the light gradient across the coleoptile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392447
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  • 3
    Electronic Resource
    Electronic Resource
    Intracellular localisation of phytochrome in oat coleoptiles by electron microscopy (1990)
    Springer
    Planta 180 (1990), S. 372-377 
    Details
    ISSN: 1432-2048
    Keywords: Avena (phytochrome) ; Phytochrome (destruction, localisation, sequestering)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The intracellular localisation of phytochrome in oat (Avena sativa L. cv. Garry Oat) coleoptiles was analysed by electron microscopy. Serial ultrathin sections of resin-embedded material were indirectly immunolabeled with polyclonal antibodies against phytochrome together with a gold-coupled second antibody. The limits of detectability of sequestered areas of phytochrome (SAPs) were analysed as a function of light pretreatments and amounts of the far-red absorbing form of phytochrome (Pfr) established. In 5-d-old dark-grownAvena coleoptiles SAPs were not detectable if less than 13 units of Pfr — compared with 100 units total phytochrome of 5-d-old dark-grown seedlings — were established by a red light pulse. In other sets of experiments, seedlings were preirradiated either with a non-saturating red light pulse to allow destruction to occur or with a saturating red followed by a far-red light pulse to induce first SAP formation and then its disaggregation. These preirradiations resulted in an increase of the limit of detectability of SAP formation after a second red light pulse to 38–41 and 19–23 units Pfr, respectively. We conclude that with respect to Pfr-induced SAP formation an adaptation process exists and that our data indicate that SAP formation is not a simple self-aggregation of newly formed Pfr.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160392
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  • 4
    Electronic Resource
    Electronic Resource
    Phytochrome-mediated phototropism in maize seedling shoots (1984)
    Springer
    Planta 160 (1984), S. 41-51 
    Details
    ISSN: 1432-2048
    Keywords: Coleoptile ; Mesocotyl ; Phototropism (red and blue light) ; Phytochrome and phototropism ; Zea (phototropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Unilateral irradiation with red light (R) or blue light (BL) elicits positive curvature of the mesocotyl of maize (Zea mays L.) seedlings raised under R for 2 d from sowing and kept in the dark for 1 d prior to curvature induction. The fluenceresponse curve for R-induced mesocotyl curvature, obtained by measuring curvature 100 min after phototropic induction, shows peaks in two fluence ranges, designated first positive range (from the threshold to the trough), and second positive range (above the trough). The fluence-response curve for BL is similar to that for R but shifted two orders of magnitude to higher fluences. Blue light elicits the classical first positive curvature of the coleoptile, whereas this response is not found with R. Positive mesocotyl curvature induced by either R or BL is eliminated by R given from above just before the unilateral irradiation, whereas BL-induced coleoptile curvature is not eliminated. The above results collectively offer evidence that phototropic curvature of the mesocotyl is induced by R-sensitive photosystem(s). Mesocotyl curvature in the second positive range is reduced by vertical far-red light (FR) applied after phototropic induction with R, but is not affected by FR applied before R. Unilateral irradiation with FR following vertical irradiation with a high R fluence leads to negative curvature of the mesocotyl. It is concluded that mesocotyl curvature in the second positive range results from a gradient in the amount of the FR-absorbing form of phytochrome (Pfr) established across the plant axis. Mesocotyl curvature in the first positive range is inhibited by vertical FR given either before or after phototropic induction with R. Since the FR used here is likely to produce more Pfr than the very low fluences of R eliciting the mesocotyl curvature in the first positive range, it is assumed that FR reduces the response in this case by adding Pfr at both sides of the plant axis. By rotating seedlings on a clinostat with its axis horizontal, the kinetics of mesocotyl curvature can be studied in the absence of a counteracting gravitropic response. On the clinostat, the R-induced mesocotyl curvature develops after a lag, through two successive phases having different curvature rates, the late phase is slower than the early phase. Negative curvature of the coleoptile can be induced by either R or BL; the BL-induced negative curvature is found at fluences higher than those giving positive curvature. The clinostat experiments show that the negative coleoptile curvature induced by either R or BL is a gravitropic compensation for positive mesocotyl curvature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392464
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  • 5
    Electronic Resource
    Electronic Resource
    Photoperception sites for phytochrome-mediated phototropism of maize mesocotyls (1984)
    Springer
    Planta 162 (1984), S. 477-479 
    Details
    ISSN: 1432-2048
    Keywords: Light perception site ; Mesocotyl ; Phototropism (red light) ; Phytochrome and phototropism ; Zea (phototropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The major site of photoperception for phytochrome-mediated phototropism of maize (Zea mays L.) mesocotyls was identified to be within the bending zone of the mesocotyl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393462
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  • 6
    Electronic Resource
    Electronic Resource
    Partial purification of sequestered particles of phytochrome from oat (Avenu sativa L.) seedlings (1991)
    Springer
    Planta 183 (1991), S. 265-273 
    Details
    ISSN: 1432-2048
    Keywords: Avena (phytochrome) ; Phytochrome (sequestering, immunolocalization)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sequestered particles of phytochrome (SAPs) were partially purified from red-light-irradiated oat coleoptiles. Phytochrome pelletability was enhanced by using buffers containing 10 mM Mg2+ or high concentrations (0.6–0.8 M) of orthophosphate (Pi). Combining the pelletability of phytochrome in the presence of Mg2+ with that in the presence of 0.6 Pi resulted in a strong enrichment (about 100-fold) of pelletable phytochrome. Antisera were raised against Mg2+-Pi-pellets from darkgrown seedlings. Using these antisera, no evidence was found by Western blotting and immunocytochemistry that SAPs contain major proteins other than phytochrome. The major contamination of these enriched SAP preparations consisted of protein crystals which are probably catalase. The preparations contained methyltransferase and protein-kinase activities which were not associated with SAPs. Phytochrome purified from SAPs served as a substrate for protein-kinase activity but not for the methyltransferase activity. Phytochrome itself did not show any kinase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197798
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  • 7
    Electronic Resource
    Electronic Resource
    Intracellular localisation of phytochrome and ubiquitin in red-light-irradiated oat coleoptiles by electron microscopy (1987)
    Springer
    Planta 171 (1987), S. 332-338 
    Details
    ISSN: 1432-2048
    Keywords: Avena (phytochrome) ; Phytochrome (localisation, sequestering) ; Ubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The intracellular localisation of phytochrome and ubiquitin in irradiated oat coleoptiles was analysed by electron microscopy. We applied indirect immunolabeling with polyclonal antibodies against phytochrome from etiolated oat seedlings or polyclonal antibodies against ubiquitin from rabbit reticulocytes, together with a goldcoupled second antibody, on serial ultrathin sections of resin-embedded material. Immediately after a 5-min pulse of red light-converting phytochrome from the red-absorbing (Pr) to the far-redabsorbing (Pfr) form-the label for phytochrome was found to be sequestered in electron-dense areas. For up to 2 h after irradiation, the size of these areas increased with increasing dark periods. The ubiquitin label was found in the same electrondense areas only after a dark period of 30 min. A 5 min pulse of far-red light, which reverts Pfr to Pr, given immediately after the red light did not cause the electron-dense structures to disappear; moreover, they contained the phytochrome label immediately after the far-red pulse. In contrast, after the reverting far-red light pulse, ubiquitin could only be visualised in the electron-dense areas after prolonged dark periods (i.e. 60 min). The relevance of these data to light-induced phytochrome pelletability and to the destruction of both Pr and Pfr is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398678
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  • 8
    Electronic Resource
    Electronic Resource
    Induction of transverse polarity by blue light: An all-or-none response (1991)
    Springer
    Planta 185 (1991), S. 415-424 
    Details
    ISSN: 1432-2048
    Keywords: Blue light (polarity induction) ; Coleoptile ; Phototropism ; Polarity (transverse) ; Signal transduction ; Zea (phototropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phototropic stimulation induces a spatial memory. This was inferred from experiments with maize (Zea mays L.) coleoptiles involving opposing blue-light pulses, separated by variable time intervals, and rotation on a horizontal clinostat (Nick and Schäfer, 1988b, Planta 175, 380–388). In those experiments, individual seedlings either curved towards the first or towards the second pulse, or they remained straight. Bending, if it occurred, seemed to be an all-or-none response. Intermediates, i.e. plants, bending only weakly, were not observed. In the first part of the present study it was attempted to create such intermediates. For this purpose the strength of the first, inducing, and the second, opposing, pulse was varied. The result was complex: (i) Individual seedlings maintained the all-or-none expression of spatial memory. (ii) However, on the level of the whole population, the time intervals at which a given response type dominated depended on the fluence ratio. (iii) Furthermore, the final curvature was determined by the fluence ratio. These results are discussed in terms of a blue-light-induced transverse polarity. This polarity initiates from a labile precursor, which can be reoriented by an opposing stimulation (indicated by the strong bending towards the second pulse). The strong curvatures towards the first pulse over long time intervals reveal that, eventually, the blue-light-induced transverse polarity becomes stabilised and thus immune to the counterpulse. In the second part of the study, the relation between phototropic transduction and transverse polarity was characterised by a phenomenological approach involving the following points: (i) Sensory adaptation for induction of transverse polarity disappears with a time course similar to that for phototropic sensory adaptataion. (ii) The fluence-response for induction of transverse polarity is a saturation curve and not bell-shaped like the curve for phototropism. (iii) For strong counterpulses and long time intervals the clinostat-elicited nastic response (Nick and Schäfer 1989, Planta 179, 123–131) becomes manifest and causes an “aiming error” towards the caryopsis. (iv) Temperature-sensitivity of polarity induction was high in the first 20 min after induction, then dropped sharply and rose again with the approach of polarity fixation. (v) Stimulus-summation experiments indicated that, for different inducing fluences, the actual fixation of polarity happened at about 2 h after induction. These experiments point towards an early separation of the transduction chains mediating phototropism and transverse polarity, possibly before phototropic asymmetry is formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201066
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  • 9
    Electronic Resource
    Electronic Resource
    Phytochrome-mediated phototropism in maize mesocotyls. Relation between light and Pfr gradients, light growth response and phototropism (1985)
    Springer
    Planta 165 (1985), S. 424-429 
    Details
    ISSN: 1432-2048
    Keywords: Phototropism (phytochrome, Zea) ; Phytochrome (light gradient) ; Zea (phototropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Unilateral irradiation of maize (Zea mays L.) seedlings results in a fluence-rate gradient, and hence below saturation, a gradient of the far-red-absorbing form of phytochrome (Pfr). The Pfr-gradients established by blue, red and far-red light were spectrophotometrically measured in the mesocotyl. Based on these Pfr-gradients and the fluence-response curves of phytochrome photoconversion the fluence-rate gradients were calculated. The fluence-rate gradient in the blue (460 nm) was steeper than that in the red (665 nm), which in turn was steeper than that in the far-red light (725 nm). The fluence-rate ratios front to rear were 1:0.06 (460 nm), 1:0.2 (665 nm), and 1:0.33 (725 nm). The assumption that phytochrome-mediated phototropism of maize mesocotyls is caused by local phytochrome-mediated growth inhibition was tested in the following manner. Firstly, the Pfr response curve for growth inhibition was calculated; these calculations were based on measurements of Pfr-gradients and data from red-light-induced phototropism. Secondly, the Pfr response curve for growth inhibition was used as a basis for calculating fluence-response curves for blue-and far-red-light-induced phototropism. Finally, these calculated results were compared with experimental data. It was concluded that the threshold for phytochrome-mediated phototropism of maize mesocotyls reflects the apparent photoconversion cross section of phytochrome whereas the maximal inducable curvature depends on the steepness of the light (Pfr) gradient across the mesocotyl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392241
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  • 10
    Electronic Resource
    Electronic Resource
    Intracellular localisation of phytochrome in oat coleoptiles by electron microscopy (1990)
    Springer
    Planta 180 (1990), S. 372-377 
    Details
    ISSN: 1432-2048
    Keywords: Avena (phytochrome) ; Phytochrome (destruction, localisation, sequestering)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The intracellular localisation of phytochrome in oat (Avena sativa L. cv. Garry Oat) coleoptiles was analysed by electron microscopy. Serial ultrathin sections of resin-embedded material were indirectly immunolabeled with polyclonal antibodies against phytochrome together with a gold-coupled second antibody. The limits of detectability of sequestered areas of phytochrome (SAPs) were analysed as a function of light pretreatments and amounts of the far-red absorbing form of phytochrome (Pfr) established. In 5-d-old dark-grown Avena coleoptiles SAPs were not detectable if less than 13 units of Pfr — compared with 100 units total phytochrome of 5-d-old dark-grown seedlings — were established by a red light pulse. In other sets of experiments, seedlings were preirradiated either with a non-saturating red light pulse to allow destruction to occur or with a saturating red followed by a far-red light pulse to induce first SAP formation and then its disaggregation. These preirradiations resulted in an increase of the limit of detectability of SAP formation after a second red light pulse to 38–41 and 19–23 units Pfr, respectively. We conclude that with respect to Pfr-induced SAP formation an adaptation process exists and that our data indicate that SAP formation is not a simple self-aggregation of newly formed Pfr.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198788
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