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  • 1
    Electronic Resource
    Electronic Resource
    Gibberellin-induced growth and regulation of the cell division cycle in deepwater rice (1992)
    Springer
    Planta 188 (1992), S. 362-368 
    Details
    ISSN: 1432-2048
    Keywords: Cell division cycle ; Flow cytometry ; Gibberellin ; Intercalary meristem ; Internodal elongation ; Oryza (growth)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Excised stem sections of deepwater rice (Oryza sativa L., cv. Pin Gaew 56) containing the highest internode were used to study induction of rapid internodal elongation by gibberellin. It has been shown previously that this growth response is based on an increased cell production rate in the intercalary meristem and on increased cell elongation. Our investigations were aimed at establishing the temporal sequence of these GA-regulated processes. Cell sizes were determined by scanning electron microscopy, the phases of the cell cycle by flow cytometry, and DNA synthesis by [3H]thymidine incorporation. The lag time for the onset of gibberellic acid (GA3)-induced growth was 40 min. Treatment with GA3 promoted cell elongation in the intercalary meristem within 2 h. After 4 h of treatment with GA3, the fraction of meristematic cells in the G2 phase had declined, indicating that cells in the G2 phase had entered mitosis. Subsequent activation of DNA replication led to an overall increase in the cell-production rate. This was evident from an increase in the percentage of cells in the S phase and from enhanced incorporation of [3H]thymidine into DNA between 4 and 7 h of GA3 treatment. An increase in the final cell length contributed to the growth response after 7 h of GA3 application. Our results are consistent with the hypothesis that gibberellin first promotes cell elongation in the intercalary meristem and that cell division is stimulated as a result of cell-growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192803
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  • 2
    Electronic Resource
    Electronic Resource
    Internodal elongation and orientation of cellulose microfibrils and microtubules in deepwater rice (1993)
    Springer
    Planta 190 (1993), S. 354-362 
    Details
    ISSN: 1432-2048
    Keywords: Cellulose microfibril ; Gibberellin ; Internodal elongation ; Microtubule ; Oryza (growth)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Excised stem sections of deepwater rice (Oryza sativa L.) containing the highest internode were used to study the induction of rapid internodal elongation by gibberellin (GA). It has been shown before that this growth response is based on enhanced cell division in the intercalary meristem and on increased cell elongation. In both GA-treated and control stem sections, the basal 5-mm region of the highest internode grows at the fastest rate. During 24 h of GA treatment, the internodal elongation zone expands from 15 to 35 mm. Gibberellin does not promote elongation of internodes from which the intercalary meristem has been excised. The orientation of cellulose microfibrils (CMFs) is a determining factor in cell growth. Elongation is favored when CMFs are oriented transversely to the direction of growth while elongation is limited when CMFs are oriented in the oblique or longitudinal direction. The orientation of CMFs in parenchymal cells of GA-treated and control internodes is transverse throughout the internode, indicating that CMFs do not restrict elongation of these cells. Changes in CMF orientation were observed in epidermal cells, however. In the basal 5-mm zone of the internode, which includes the intercalary meristem, CMFs of the epidermal cell walls are transversely oriented in both GA-treated and control stem sections. In slowly growing control internodes, CMF orientation changes to the oblique as cells are displaced from this basal 5-mm zone to the region above it. In GA-treated rapidly growing internodes, the reorientation of CMFs from the transverse to the oblique is more gradual and extends over the 35-mm length of the elongation zone. The CMFs of older epidermal cells are obliquely oriented in control and GA-treated internodes. The orientation of the CMFs parallels that of the cortical microtubules. This is consistent with the hypothesis that cortical microtubules determine the direction of CMF deposition. We conclude that GA acts on cells that have transversely oriented CMFs but does not promote growth of cells whose CMFs are already obliquely oriented at the start of GA treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196964
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  • 3
    Electronic Resource
    Electronic Resource
    The cell cycle genes cycA1;1 and cdc2Os-3 are coordinately regulated by gibberellin in planta (2000)
    Springer
    Planta 211 (2000), S. 376-383 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Cell division ; Cyclin ; Cyclin-dependent protein kinase ; Gibberellin ; Growth ; Oryza (cell cycle)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract.  Internodal growth of deepwater rice (Oryza sativa L.) can achieve rates of up to 10 mm h−1. In submergence-induced plants, gibberellic acid activates the cell division cycle first at the G1 → S phase transition with a subsequent increase in mitotic activity. The proteins cycA1;1 and cdc2Os-3 are the regulatory and catalytic subunits, respectively, of cyclin-dependent protein kinases (CDKs) which are central to cell cycle regulation. Both genes are regulated by gibberellic acid in a coordinate manner with transcripts accumulating in the G2 phase prior to the B2-type mitotic cyclins described previously (M. Sauter et al. 1995, Plant J 7: 623–632), suggesting a distinct role in regulating G2/M phase progression. Since cdc2Os-3 belongs to a group of CDKs that have no counterparts in animals, it may function in a plant-specific gibberellin-regulated cell division process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250000295
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal and Photochemical Rearrangement of 3-Substituted 2-Methylbenzofuran Epoxides and Their Valence-Isomeric Quinone Methides (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 433-436 
    Details
    ISSN: 0009-2940
    Keywords: Epoxidation ; Dioxirane, dimethyl- ; Benzofurans, 2-methyl- ; Benzofuran epoxides ; Quinone methides ; Photoisomerization ; Chromenes ; 3-Benzofuranones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dimethyldioxirane oxidation of the 3-substituted 2-methylbenzofurans 1 [1a: 3(E)-styryl, 1b: 3-acetoxy, 1c: 3-(tert-butyldimethylsilyloxy)] is reported. Only quinone methide 3a, none of the benzofuran epoxides 2a-c, could be detected by 1H- and 13C-NMR spectroscopy at low temperature (-30°C), which on photoisomerization led to chromene 7a. The benzofuran-3-ones 5b, c and the α-diketone 6c are presumably formed by thermal isomerization of the transient benzofuran epoxides 2b, c and quinone methide 3c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270220
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  • 5
    Electronic Resource
    Electronic Resource
    Preparation of 2H-Benzoxetes by Photoinduced [2 + 2] Cycloaddition of Quinone Methides, Accessible by Dimethyldioxirane (DMD) Oxidation of 2,3-Dimethylbenzofurans (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1115-1118 
    Details
    ISSN: 0009-2940
    Keywords: Epoxidation ; Dioxirane, dimethyl- ; Benzofurans, 2,3-dimethyl- ; Benzofuran epoxides ; Quinone methides ; [2 + 2] Photocycloaddition ; Benzoxetes ; Hetero-Diels-Alder reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation (λ 〉 366 nm) of the quinone methides 3, which were formed by valence isomerization of the methyl-, chloro-, and tert-butyl-substituted 2,3-dimethylbenzofuran epoxides 2, afforded the novel 2H-benzoxetes 4 by photochemical [2 + 2] cycloaddition. These strained and highly labile benzoxetes 4 were spectrally (1H and 13C NMR) characterized at subambient temperatures. On prolonged storage (2-3 d) at -20 to -10°C, the benzoxetes 4 reverted to the quinone methides 3 and/or benzofuran epoxides 2.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270622
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  • 6
    Electronic Resource
    Electronic Resource
    Epoxidation of 2,3-Dimethylbenzofurans by Dimethyldioxirane (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 231-234 
    Details
    ISSN: 0009-2940
    Keywords: Epoxidation ; Dioxirane, dimethyl ; Benzofurans, 2,3-dimethyl- ; Benzofuran epoxides ; Quinone methides ; Methanol addition ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of epoxides 2 by the reaction of the chloro- and methyl-substituted 2,3-dimethylbenzofurans 1 with dimethyl-dioxirane at low temperature is reported. These labile epoxides were spectroscopically characterized (1H and 13C NMR) at subambient temperatures. Epoxidation of benzofuran 1c affords a 31:69 mixture of epoxide 2c and quinone methide 3c, the latter presumably being produced by valence isomerization of the epoxide. On warming up above -10°C, the epoxides 2 suffer decomposition. Treatment of epoxide 21 with methanol yields the tautomeric mixture of adducts 4i and 4i′.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250136
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  • 7
    Electronic Resource
    Electronic Resource
    Photochemical and Thermal Rearrangement of Acyl-Substituted Quinone Methides, Accessible by Dimethyldioxirane Oxidation of Benzofurans and Subsequent Valence Isomerization of the Resulting Epoxides (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2697-2699 
    Details
    ISSN: 0009-2940
    Keywords: Epoxidation ; Dioxirane, dimethyl- ; Benzofurans, 2-methyl-3-phenyl ; Benzofuran epoxides ; Quinone methides ; (Z/E) Photoisomerization ; Norcaradiene ; Benzocycloheptafuran ; Thermal rearrangement ; Xanthenes, 9-acetyl- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoisomerization of quinone methides 3 to benzocycloheptafuran 4 and the thermolysis of the latter to xanthenes 5 are reported. The quinone methides 3 are accessible by dimethyldioxirane oxidation and subsequent valence isomerization of the resulting benzofuran epoxides 2. On irradiation (λ 〉 400 nm), the quinone methides 3 rearrange by cyclization to the corresponding norcaradiene, and ring enlargement affords the benzocycloheptafurans 4. Thermolysis of the cycloheptatrienes 4 leads to the xanthenes 5, first by cycloreversion to the norcaradienes, followed by electrocyclization to the chromenes and tautomerization of the latter. The new cycloheptatrienes 4 and xanthenes 5 were fully characterized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261220
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