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  • Chemistry  (3)
  • Gametophytic gene expression  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Gametophytic expression of genes controlling endosperm development in maize (1988)
    Springer
    Theoretical and applied genetics 75 (1988), S. 252-258 
    Details
    ISSN: 1432-2242
    Keywords: Gametophytic gene expression ; Defective endosperm mutants ; Pollen-style interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An indirect approach was adopted to select viable mutants affecting the male gametophytic generation in maize. This approach consists of a selection of endosperm defective mutants followed by a test for gametophytic gene expression, based on the distortion from mendelian segregation and on the measurement of pollen size and pollen sterility. The material used consisted of 34 endosperm defective viable mutants introgressed in B37 genetic background. Complementation tests indicated that the mutation in the collection of mutants affected different genes controlling endosperm development. The study of the segregation in F2 revealed four classes of de (defective endosperm) mutants: (1) mutants in which the mutation does not affect either gametophytic development or function; (2) mutants in which the effect on the gametophyte affects pollen development processes; (3) mutants showing effects on both pollen development and function, and (4) mutants where only pollen tube growth rate is affected. Positive and negative interactions between pollen and style were detected by means of mixed pollination (pollen produced by de/de plants and pollen from an inbred line used as a standard and carrying genes for colored aleurone), on de/de and de/ + plants. Positive interactions were interpreted as methabolic complementation between defective pollen and normal styles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00303961
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  • 2
    Electronic Resource
    Electronic Resource
    gaMS-1: a gametophytic male sterile mutant in maize (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 216-220 
    Details
    ISSN: 1432-2145
    Keywords: Key words Maize pollen ; Male sterility ; Microsporogenesis ; Gametophytic gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Several pollen-specific genes from different species have been isolated and characterized at the molecular level, but the precise role of most of them is unknown. Mutant analysis represents a direct approach to uncovering gene function, but the paucity of available mutants affecting pollen development and/or function and the poor characterization of the known mutants have so far limited the exploitation of this approach. Here we present the cytological characterization of gametophytic male sterile-1 (gaMS-1), a maize mutant that we identified in a program of transposon insertion mutagenesis for the production of mutations in gametophytically acting genes involved in microsporogenesis. gaMS-1 is expressed during or immediately after the first microspore division and leads to the production of immature, non-functional pollen grains. The mutation appears to affect the events leading to the developmental switch that follows the first microspore mitosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050034
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  • 3
    Electronic Resource
    Electronic Resource
    gaMS-1: A gametophytic male sterile mutant in maize (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 216-220 
    Details
    ISSN: 1432-2145
    Keywords: Maize pollen ; Male sterility ; Microsporogenesis ; Gametophytic gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several pollen-specific genes from different species have been isolated and characterized at the molecular level, but the precise role of most of them is unknown. Mutant analysis represents a direct approach to uncovering gene function, but the paucity of available mutants affecting pollen development and/or function and the poor characterization of the known mutants have so far limited the exploitation of this approach. Here we present the cytological characterization ofgametophytic male sterile-1 (gaMS-1), a maize mutant that we identified in a program of transposon insertion mutagenesis for the production of mutations in gametophytically acting genes involved in microsporogenesis.gaMS-1 is expressed during or immediately after the first microspore division and leads to the production of immature, nonfunctional pollen grains. The mutation appears to affect the events leading to the developmental switch that follows the first microspore mitosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02173101
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  • 4
    Electronic Resource
    Electronic Resource
    Untersuchung der teilschritte der ethylen-hochdruckpolymerisation, 2Teil 1: cf.1.. Druck- und temperaturabhängigkeit der einzelnen geschwindigkeitskonstanten (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 849-859 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the first part of this series the individual rate constants of the radical polymerization of ethylene are reported in dependency of pressure at 405 K. By further measurements under 500 - 1750 bar and 400 - 470 K, using again the method of the rotating sector, the dependency of the rate constants on both pressure and temperature was determined. With increasing temperature the rate constant of chain growth kp as well as that of chain termination kt increases. With increasing pressure, kp increases, whereas kt decreases because of the diffusion controlled termination reaction. For the chain growth an activation energy of Ep = 37 kJ/mol and an activiation volume of Δvp≠ = -25,5 ml/mol was found. The activiation parameters of the chain termination are Et = 9,9 kJ/mol and Δvt≠ = 7 ml/mol. Based on these results and literature data the rate constants of different chain transfer reactions involved in the high pressure polymerization of ethylene and their dependency on temperature and pressure were evaluated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021840419
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  • 5
    Electronic Resource
    Electronic Resource
    Regiospecific Synthesis of 3,4-Disubstituted Furans and ThiophenesDedicated to Professor Xi-Kui Jiang, Shanghai Institute of Organic Chemistry, on the occasion of his 70th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 459-466 
    Details
    ISSN: 0947-3440
    Keywords: Furans ; Thiophens ; Palladium catalysis ; Coupling reactions ; Heterocycles ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The regiospecific synthesis of 3,4-disubstituted furans and thiophenes is reviewed. Our initial approach used 3,4-bis(tri-n-butylstannyl)furan as a building block, which led to many structurally diverse 3,4-disubstituted furans. Another avenue was explored by using 3,4-bis(trimethylsilyl)furan and 3,4-bis(trimethylsilyl)thiophene as precursors. A variety of unsymmetrically 3,4-disubstituted furans and thiophenes were prepared in this way. The advantages of our strategy lie in its stepwise manner as well as its prospect of yielding 3,4-disubstituted furans and thiophenes with rather different substitution pattern.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970304
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  • 6
    Electronic Resource
    Electronic Resource
    Untersuchung der teilschritte der ethylen-hochdruck-polymerisation, 1. Druckabhängigkeit der einzelnen geschwindigkeitskonstanten (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 207-216 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to calculate the average molecular weight, the molecular weight distribution or the branching of low density polyethylene, the individual values of the rate constants of the different reactions involved in the free radical polymerization are required. The method of rotating sector was applied to determine the rate constants of chain propagation and chain termination in a wide range of temperatures and pressures. This first part of the work reports the influence of the pressure. It was found that the rate constant kp of the chain propagation increases with rising pressure whereas the rate constant kt of chain termination decreases. The effect of the pressure on kp can be explained in terms of the activation volume. The decrease of kt with pressure is caused by a diffusion controlled termination reaction.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021840120
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