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  • 1
    Digitale Medien
    Digitale Medien
    Phytochrome control of short-day-induced bud set in black cottonwood (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 97 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: In trees and other woody perennial plants, short days (SDs) typically induce growth cessation, the initiation of cold acclimation, the formation of a terminal bud and bud dormancy. Phytochrome control of SD-induced bud set was investigated in two northern clones of black cottonwood (Populus trichocarpa Torr. & Gray) by using night breaks with red light (R) and far-red light (FR). For both clones (BC-1 and BC-2), SD-induced bud set was prevented when R night breaks as short as 2 min were given in the middle of the night. When night breaks with 2 min of R were immediately followed by 2 min of FR, substantial reversibility of bud set was observed for BC-1 but not for BC-2. By comparing the effects of the R night breaks on bud set and the length of specific internodes, we determined that the R night breaks influenced internode elongation in two opposing ways. First, the addition of a R night break to the SD treatment prevented the cessation of internode elongation that is associated with bud set. Those internodes that would not have elongated under SDs (and would have been found within the terminal bud) elongated in the R treatment. Second, the R night breaks decreased internode length relative to the long-day (LD) control. In contrast to the clonal differences in reversibility that we observed for bud set, the decrease in internode length (i.e. the second effect of R) was R/FR reversible in both clones. Based on these results, we conclude that internode elongation is influenced by two distinct types of phytochrome-mediated response. The first response is a typical response to photpperiod, whereas the second response is a typical “end-of-day” response to light quality. Our results demonstrate that SD-induced bud set in black cottonwood is controlled by phytochrome but that clonal differences have an important influence on the R/FR reversibility of this response. The availability of an experimental system in which SD-induced bud set is R/FR reversible will be valuable for studying the physiological genetics of photoperiodism in trees.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00484.x
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  • 2
    Digitale Medien
    Digitale Medien
    Photoperiodic responses of a northern and southern ecotype of black cottonwood (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 93 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Photoperiod is an important signal controlling the onset of dormancy in perennial plants. Short days typically induce growth cessation, the initiation of cold acclimation, the formation of a terminal bud. bud dormancy and other adaptive responses. Photoperiodic ecotypes have evolved in many species with large latitudinal distributions. The photoperiodic responses of two northern (53°35′ and 53°50′N) and two southern (34°10′ and 40°32′N) genotypes of black cottonwood (Populus trichocarpa Torr. & Gray) were characterized by growing trees under a range of photoperiods in the greenhouse and growth chamber. Short days induced bud set in both ecotypes. resulting in trees with fewer leaves and less height growth than trees grown under long days. Short days also enhanced anthocyanin accumulation in the northern ecotype and decreased branching of the southernmost genotype. Two aspects of the photoperiodic response were evaluated for each trail: critical photoperiod. which was defined as the longest photoperiod that elicited a short-day response, and photoperiodic sensitivity, which was defined as the change in response per unit change in photoperiod. For each of the traits analyzed, the northern ecotype had a longer critical photoperiod and greater photoperiodic sensitivity than did the southern ecotype. The short critical photoperiod and reduced photoperiodic sensitivity of the southern ecotype resulted in a significant delay in bud set compared to that of the northern ecotype, even under a 9-h photoperiod. Typically, photoperiodic ecotypes have been characterized as having different critical photoperiods. Ecotypic differences in photoperiodic sensitivity, however, indicate that differences in the photoperiodic response curves cannot be completely described by the critical photoperiod alone. These results also suggest that the critical photoperiod. photoperiodic sensitivity and speed of bud set have a common physiological basis. Bud set occurred earlier hi the northern ecotype primarily because bud scale leaves were initiated earlier. For one of the northern genotypes, leaf primordia that were initialed under long days subsequently differentiated into bud scale leaves after the trees were transferred to a 9-h photoperiod. This demonstrates that primordia initiated under long days are not necessarily committed to becoming foliage leaves. The response to photoperiod did not differ appreciably between the greenhouse and growth chamber conditions that were tested.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1399-3054.1995.930417.x
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  • 3
    Digitale Medien
    Digitale Medien
    A liquid cytokinin pulse induces adventitious shoot formation from Douglas-fir cotyledons (1991)
    Springer
    Plant cell reports 10 (1991), S. 156-160 
    Details
    ISSN: 1432-203X
    Schlagwort(e): Douglas-fir ; Tissue culture ; Adventitious buds ; Cytokinin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The effects of high-concentration, 2-h liquid pulses of N6-benzylaminopurine (BA) and thidiazuron (TD) on adventitious bud and shoot formation were tested in cotyledons of Douglas-fir (Pseudotsuga menziesii). Seedling age proved important; on average, cotyledons from the youngest seedlings formed 10-fold more buds than cotyledons from the oldest seedlings. Optimal cytokinin concentrations for the youngest cotyledons were 400 and 800 μM BA, and 100 and 200 μM TD. Shoots developed best from buds induced with 300, 400, and 800 μM BA. Four gelling agents were tested; BRL agarose yielded more than three times the number of buds, and Gelrite nearly twice the number of buds, as either Sigma agar or Difco Bacto-Agar. One of the best treatments (400 μM BA, agarose) yielded more cotyledons with buds, and more buds per cotyledon, than when cytokinins were incorporated into the growth medium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00232049
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  • 4
    Digitale Medien
    Digitale Medien
    Transient gene expression of microprojectile-introduced DNA in Douglas-fir cotyledons (1991)
    Springer
    Plant cell reports 10 (1991), S. 517-521 
    Details
    ISSN: 1432-203X
    Schlagwort(e): Biolistics-GUS-355-Conifer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Plasmid DNA containing the reporter gene uidA encoding β-glucuronidase (GUS), driven by the cauliflower mosaic virus 35S promoter, was introduced on high-velocity microprojectiles into cultured cotyledons of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco]. Transient gene expression was measured by counting the number of distinct loci of GUS activity per cotyledon. Contrary to published results on angiosperms, repeated bombardments did not increase expression in Douglas-fir. Expression varied significantly among cotyledons from different seedlings. The amount of time between DNA delivery and treatment of cotyledons with auxins and cytokinins strongly affected GUS expression. The optimal cytokinin pretreatment produced an average of 20 loci per cotyledon. In several experiments, more than 95% of the treated cotyledons exhibited at least some transient expression. Expression remained constant up to three days following DNA delivery into cotyledons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00234585
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  • 5
    Digitale Medien
    Digitale Medien
    Agrobacterium-mediated transformation of hybrid poplar suspension cultures and regeneration of transformed plants (1994)
    Springer
    Plant cell, tissue and organ culture 36 (1994), S. 59-71 
    Details
    ISSN: 1573-5044
    Schlagwort(e): antibiotics ; cocultivation ; organogenesis ; Populus ; tissue culture ; thidiazuron
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A method for Agrobacterium-mediated transformation of hybrid poplar (Populus alba x P. grandidentata cv. ‘Crandon’) suspension cultures and regeneration of transformed plants is described. Transformants were recovered when suspension cultures were inoculated with Agrobacterium tumefaciens at a density of 107 colony-forming units ml-1, cocultivated for 48 h, and plated to cellulose acetate filters on Woody Plant Medium containing 4.5 μM 2,4-dichlorophenoxyacetic acid and 250 mg l-1 cefotaxime. Levels of cefotaxime greater than 250 mg l-1 were unnecessary for control of residual bacteria and inhibited callus growth. Transgenic plants were regenerated by culturing the transformed callus on media containing 0.11 to 27 μM thidiazuron. In contrast to thidiazuron, N6-benzyladenine had a negative effect on shoot regeneration; the callus became necrotic when we attempted to induce shoots with concentrations of 1.1 to 8.9 μM, and growth was inhibited when concentrations of 0.11 or 0.22 μM were used to regenerate callus from suspension cultures. Following cocultivation of poplar suspension cultures, we recovered transgenic plants containing the maize transposon Ac, and callus containing an insect toxin gene from Bacillus thuringiensis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00048316
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