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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 99 (1997), S. 0 
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: A custom designed growth-measuring apparatus, controlled by a microcomputer has been used to study extension growth kinetics of wild-type and photomorphogenic-mutant tomato (Lycopersicon esculentum Mill.) plants with and without end-of-day farred light (EODFR). The following photomorphogenic mutants were used. Far-red insensitive (fri.1): deficient in phytochrome A (phyA); temporarily red light-insensitive (tri.3): deficient in phytochrome Bl (phyB1), and their isogenic wild type (WT) cv. MoneyMaker. aurea (au): deficient in phytochrome chromophore biosynthesis; high-pigment-1 (hp-1): exhibiting exaggerated phytochrome responses, and their isogenic WT cv. Ailsa Craig. The stem elongation rate (SER) during a 24-h period of all the genotypes studied shows a similar pattern, having two dramatic transients, one shortly after the onset of the light period (a sharp decline in SER) and another shortly after the start of the dark period (a sharp increase in SER). These transients are probably associated with water relations as a consequence of opening and closure of the stomata. The fastest SER occurs during the dramatic oscillations early in the dark period. Between the genotypes there are large quantitative differences in SER. All the genotypes tested exhibited a strong EODFR response, resulting in a relative promotion of SER during the first period after the start of EODFR and in the subsequent light and dark periods. These results indicate that phyA, absent in the fri.1 mutant, does not play a major role in SER of light-grown tomato plants, whereas phyB 1, absent in the tri.3 mutant, is partly responsible for the compact stature of WT plants. An additional phytochrome other than phy A and phy B1 must therefore be capable of eliciting the EODFR response.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 8 (1985), S. 0 
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract With appropriate pretreatment of the seeds fluence-response curves for the induction of germination of Arabidopsis thaliana show two phases. A proportion of the population responds to very low fluence (VLFR), 104–10−2μmolm−2 establishing 10−4–10−2% of the total phytochrome in the far-red absorbing form (Pfr) and a proportion of the population respond to low fluence (LFR), 1–1000 μmolm−2, establishing 1–75% Pfr. The VLFR is nol normally seen because the pre-existing Pfr level satisfies the Pfr requirement or use of green safelight establishes more Pfr than necessary to saturate the VLFR. Endogenous Pfr was depicted by a 24 h 35°C treatment, presumably as a result of dark destruction and/or dark reversion to the red absorbing form of phytochrome (Pr), making it possible to visualize the VLFR. A short pulse of 35°C treatment in combination with an appropriate temperature regime is also able to sensitize a proportion of the seed population. The proportion of the population showing the VLFR is determined by the duration of the cold imbibition pretreatment as well as the duration of the 35°C treatment. Complex fluence-response curves were observed in which a proportion of the seeds being promoted in the VLFR range, were inhibited at higher fluences before being further promoted in the LFR range. This was particularly clear for seed batches being sensitized by a short 35°C treatment. The VLFR may be of significance in the natural environment, enabling seeds buried in the upper layer of the soil to germinate, where the fluence rate falls off sharply and the LFR is not satisfied. A model is presented to explain the two phases in the fluence-response curves.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Photomorphogenesis of tomato (Lycopersicon esculentum Mill.) is being studied with the aid of mutants which are modified either in their photoreceptor composition or in their signal transduction chain(s). Phytochrome chromophore mutants, presumably deficient in all phytochromes, and mutants specifically deficient in phytochrome A (phy A) or B1 (phyB1) have been used to study the roles played by phytochromes in photomorphogenesis. In addition, other mutants, including transgenic lines overproducing phyA, exhibit exaggerated photomorphogenesis. Studies using these mutants are reviewed, with emphasis being placed on anthocyanin biosynthesis and plastid development as model systems for the dissection of the complex interactions between photoreceptors and to elucidate the nature of photoreceptor transduction chains. Recently, new mutants have been isolated by screening in a phyA, phyB1-deficient background. The novel phenotypes selected are candidates for mutants in additional photoreceptors or their transduction chains.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 16 (1993), S. 0 
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Internode extension-growth responses to neighbouring plants and to red to far-red ratios (R:FR) were investigated in wild-type (WT) and aurea (au)-mutant seedlings of tomato grown under natural radiation. The genomic location of the au mutant is not known, but one of its consequences is the reduced phytochrome level. In WT seedlings, internode growth was promoted by the presence of non-shading neighbours reflecting far-red light (FR), the shade of a tall canopy, FR provided as a supplement during the photoperiod, and FR pulses either provided at the end of the day or delayed into the dark period. Supplementary FR during the photoperiod also promoted growth in herbicide-treated partially bleached WT seedlings. The au mutant showed higher background extension-growth rates, but only responded to the most severe treatments: deep shade light and very low R:FR at the end of the day, i.e. au-mutant seedlings were less sensitive than WT seedlings to R:FR signals. Wild-type seedlings were transferred from the glasshouse to a growth room and exposed to white light with two levels of phytochrome-absorbable radiation but similar phytochrome photoequilibria and radiation for photosynthesis. The plants exposed to the lowest level showed a transient increase of internode extension growth rate and a simultaneous reduction of response to FR pulses, i.e. reproduced some of the features of au-mutant seedlings. Phytochrome itself could set the degree of response to Pfr during neighbour detection.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The tomato (Solanum lycopersicum L.) slender mutant procera (pro) was analysed for its relationship with gibberellin (GA) by combining it with GA deficiency due to the gib-1 mutation. The sensitivity to GA biosynthesis inhibitors and the GA content were measured in the pro gib-1 double mutant. In the gib-1 mutant background, the pro mutation strongly reduced the GA requirement for seed germination and stem growth and almost fully restored the morphological leaf defects of the gib-1 mutant. An end-of-day far-red light treatment, when applied to the various genotypes, indicated that GAs are required for a response to this treatment, but that it act independently of the Pro gene product.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-2048
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Homogenates of etiolated wheat leaves contain increased levels of acidic gibberellin (GA)-like substances following treatment with red light. Differential centrifugation of homogenates indicates that the response is confined to the 1000 g (or plastid) fraction. Irradiation of suspensions of intact etioplasts also increases the level of extractable GA-like activity. Phytochrome can be detected spectrophotometrically in preparations of etioplasts. The response in etioplasts can be inhibited by chloramphenicol, but not by cycloheximide, and partially by Amo 1618. The GA-like substances produced in etioplasts seem capable of passing into the surrounding medium within 20 min.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Planta 103 (1972), S. 319-326 
    ISSN: 1432-2048
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Samples for spectrophotometric measurement of phytochrome in vivo are not optically thin. For different cross sections of the sample, the rate constant of a photochemical reaction will, therefore, have different values. We have developed a mathematical model, based on the assumption that the rate of phytochrome phototransformation is proportional to the light intensity and that the light intensity gradient in the sample is exponential. Kinetic curves computed with this model conform closely with the measurements. The simplest explanation of the observed kinetics is that there is only one type of phytochrome and that the light intensity gradient in samples that are not too thin, is close to exponential.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-2048
    Schlagwort(e): Phytochrome ; Lycopersicon ; Photomorphogenic mutants ; Photomorphogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Four monogenic recessive tomato (Lycopersicon esculentum Mill.) mutants at the temporarily red light-Insensitive (tri) locus (tri 1, tri 2in the genetic background breeding line GT; tri 3, tri 4in the genetic background cultivar Moneymaker) were studied. These mutants had slightly longer hypocotyls under white light than the wild type (WT). Western-blot analysis showed that the tri 1mutant was deficient in a relatively lightstable phytochrome apoprotein (116 kDa) that was recognized in the WT by an antibody to tobacco phytochrome B; tri 2had a 166-kDa band reduced in abundance; and tri 2and tri 4had bands reduced in molecular mass, approx. 105 and 95 kDa, respectively. These patterns were also found in light-grown plants. Northern-blot analysis for PHYB1 mRNA showed for tri 2a transcript approx. 2 kb larger, for tri 4, a transcript of WT size, but much reduced in abundance and for tri 1and tri 3transcripts equivalent in size and abundance to WT. In these mutants the transcripts of other members of the tomato phytochrome gene family (PHYA, PHYB2, PHYE, PHYF) were indistinguishable in size and abundance from WT. Thus, it appears that the tri locus specifically affects PHYB1 gene expression. Unlike phytochrome-B mutants in other plants, de-etiolated seedlings of the tri mutants exhibited normal responses to end-of-day far-red (EODFR) light and supplementary far-red light during the day. Since the holophytochromes of types B1 and B2 (phyB1 and phyB2) are closely related, it is proposed that there might be redundancy between them for these responses.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Planta 88 (1969), S. 293-302 
    ISSN: 1432-2048
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Dry seeds of Amaranthus caudatus show little or no photoreversible absorption changes, attributable to phytochrome. During imbibition phytochrome appears in two phases, one immediately after sowing and the second after about 8 hr. Experiments at different temperatures and under continuous illumination with red, far-red and blue light suggest that there are two pools of phytochrome. The first phase in the appearance of phytochrome could be due to the change in optical properties of the sample on hydration or to rehydration of inactive phytochrome, or both. The second phase probably represents phytochrome synthesis. It is absent at 0° and precedes the water uptake associated with germination by some 10 hr. This second pool of phytochrome does not accumulate in red and blue illuminated seeds indicating that the rate of P fr decay is more rapid than the rate of phytochrome synthesis. The difference spectra of phytochrome in both 2 hr imbibed seeds and 72 hr old seedlings show peaks of absorption at 663 and 735 nm. The presence of P fr in dark imbibed seeds and the process of “inverse reversion” of P r to P fr in darkness have been demonstrated. The results are discussed in relation to previous hypotheses for the mechanism of photocontrol of Amaranthus seed germination.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Planta 120 (1974), S. 265-272 
    ISSN: 1432-2048
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Pea epicotyl tissue freeze dried with phytochrome (P) in the red absorbing (Pr) form, on exposure to red light does not form the far-red absorbing form of P (Pfr), but forms the intermediate P698 which reverts to Pr in darkness. Similar tissue containing the pigment as Pfr undergoes a photoreversible reaction on exposure to alternate red and far-red light. This represents the photoreversibility between Pfr and the intermediate P650. The difference spectrum of this reaction is similar to that of phytochrome photoconversion in dry cucumber seeds. P650 is shown to revert slowly to Pfr in darkness and it is proposed that this reaction accounts for the observation of apparent inverse dark reversion in cucumber seeds. Partial rehydration of freeze-dried tissue containing Pr, by means of 80% glycerol: 20% water (v/v), partially restores photoreversibility between Pr and Pfr. In such samples Pfr formation from intermediates, however, is slow and continues for several min in the dark after exposure to red light. This reaction can simulate the apparent inverse dark reversion observed in many seeds during early stages of imbibition. In this case Pfr appears from an intermediate produced by exposure to red light, which has not had time to form Pfr during the normal assay period. These two processes of Pfr production from intermediates in darkness, present under conditionsof partial or extreme dehydration, can explain previous experimental observations interpreted as inverse dark reversion. It is therefore proposed that the process, formerly described as ‘inverse dark reversion’, is not a transformation of Pr to Pfr and that there is not a separate form of phytochrome responsible for this reaction.
    Materialart: Digitale Medien
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