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  • Books
  • Articles  (8)
  • Polymer and Materials Science  (5)
  • Acid-growth theory  (1)
  • Auxin metabolism, transport  (1)
  • CO2 exchange  (1)
  • 1990-1994  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Lateral diffusion of polarly transported indoleacetic acid and its role in the growth of Lupinus albus L. hypocotyls (1991)
    Springer
    Planta 185 (1991), S. 391-396 
    Details
    ISSN: 1432-2048
    Keywords: Auxin metabolism, transport ; Elongation growth ; Cortex-stele auxin distribution ; Lupinus (auxin transport) ; Polar auxin transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transport and metabolism of indole-3-acetic acid (IAA) was studied in etiolated lupin (Lupinus albus L, cv. Multolupa) hypocotyls, following application of dual-isotope-labelled indole-3-acetic acid, [5-3H]IAA plus [1-14C]IAA, to decapitated plants. To study the radial distribution of the transported and metabolized IAA, experiments were carried out with plants in which the stele was separated from the cortex by a glass capillary. After local application of labelled IAA to the cortex, radioactivity remained immobilized in the cortex, near the application point, showing that polar transport cannot occur in the outer tissues. However, following application of IAA to the stele, radioactivity appeared in the cortex in those hypocotyl sections below the first 1 cm (in which the capillary was inserted), and the basipetal IAA movement was similar to that observed after application of IAA to the complete cut surface. In both assays, longitudinal distribution of 14C and 3H in the stele outside the first 1 cm was positively correlated with that of cortex, indicating that there was a lateral migration of IAA from the transport pathway (in the stele) to the outer tissues and that this migration depended on the amount of IAA in the stele. Both tissues (stele and cortex) exhibited intensive IAA metabolism, decarboxylation being higher in the stele than in the cortex while IAA conjugation was the opposite. Decapitation of the seedlings caused a drastic reduction of hypocotyl growth in the 24 h following decapitation, unless the hypocotyls were treated apically with IAA. Thus, exogenous IAA, polarly transported, was able to substitute the endogenous source of auxin (cotyledons plus meristem) to permit hypocotyl growth. It is proposed that IAA escapes from the transporting cells (in the stele) to the outer tissues in order to reach the growth-responsive cells. The IAA metabolism in the outer tissues could generate the IAA gradient necessary for the maintenance of its lateral flow, and consequently the auxin-induced cell elongation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201062
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  • 2
    Electronic Resource
    Electronic Resource
    Uptake and decarboxylation of indole-3-acetic acid during auxin-induced growth in lupin hypocotyl segments (1994)
    Springer
    Planta 193 (1994), S. 224-231 
    Details
    ISSN: 1432-2048
    Keywords: Acid-growth theory ; ATPase ; auxin (uptake, decarboxylation) ; Growth (auxin induced) ; Lupinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The elongation growth of etiolated hypocotyl segments of lupin (Lupinus albus L.) was stimulated by acid pH (4.6 versus 6.5) and by IAA for periods of up to 4 h. After this time, the segments were unable to grow further. In the presence of an optimal IAA concentration (10 μM), acid pH increased the growth rate but had no effect on final growth. With suboptimal IAA (0.1 μM), however, acid pH increased growth in a more than additive way, suggesting a synergistic action between the two factors. This synergism may be explained by the increased IAA uptake and decarboxylation seen at an acid pH. These results reinforce the view that the effects of low pH and IAA on growth are not independent. Vanadate inhibited growth and also IAA uptake and decarboxylation. This inhibitor, therefore, probably inhibits growth not only by decreasing ATPase-mediated acidification but also by decreasing H+-dependent IAA uptake from the apoplasm. This dependence of IAA uptake on ATPase may be mediated by apoplasmic acidification. The amount of IAA decarboxylated increased when the assay conditions favored the growth of segments, indicating that IAA could be destroyed by decarboxylation during the auxin-induced growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192534
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  • 3
    Electronic Resource
    Electronic Resource
    CO2 Exchange in soil algal crusts occurring in the trachypogon savannas of the Orinoco Llanos, Venezuela (1991)
    Springer
    Plant and soil 135 (1991), S. 233-244 
    Details
    ISSN: 1573-5036
    Keywords: CO2 exchange ; soil algal crust ; Trachypogon savannas ; water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract CO2 exchange between the atmosphere and soil algal crusts of the Trachypogon savannas of the Orinoco Llanos has been analyzed using an open gas exchange system. These savannas encompass a wide range of physiognomic types, from herbaceous communities to savanna woodlands. A maximum CO2 flux of 0.207 mg m-2 s-1 was measured in the crusts of the Guanipa savannas, while in the other examined crusts (0.035–0.105 mg m-2 s-1) the flux was similar to values reported for terrestrial algae. The CO2 flux data were statistically fitted to the photosynthetically active radiation by a logarithmic relationship, and the photosynthetic efficiencies of the crusts were compared. The activation energy calculated for the CO2 fixation indicates that limitations by diffusion and photochemical processes were excluded in the Guanipa crusts (above 12 kcal mole-1), whereas they were evident in the other crust studied. An optimum CO2 incorporation as a function of the crust water potential was established and carbon gain strategies were proposed on the basis of the results and characteristics of the habitats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010911
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis, dilute solution properties and chain flexibility of poly(diesters) of itaconic acid, 2Part 1: cf. ref.5., poly(methyl decyl itaconate) (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 593-599 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The diester of itaconic acid with decyl and methyl groups was prepared and polymerized. The dilute solution behaviour of poly(methyl decyl itaconate) poly{1-(decyloxycarbonylmethyl)-1-(methoxycarbonyl)ethylene} (PMeDI) was studied in tetrahydrofuran and 1-butanol at 298 K, by light scattering, size-exclusion chromatography, and viscometric measurements. The empirical Kuhn-Mark-Houwink-Sakurada relationships were established. The molecular parameters were calculated using one theory of the excluded volume.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930304
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  • 5
    Electronic Resource
    Electronic Resource
    Intramolecular formation of excimers in model compounds for polyesters obtained from 2,6-naphthalene dicarboxylic acid and cyclohexanediols (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1511-1519 
    Details
    ISSN: 0887-6266
    Keywords: conformation ; excimer ; fluorescence ; hairpins ; polyester ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The fluorescence in dilute solution has been measured as a function of solvent viscosity for four bichromophoric models for polyesters with naphthalene in the rigid aromatic unit and diols derived from cyclohexane as the flexible spacer. The spacers are 1,2-cis-cyclohexanediol, 1,2-trans-cyclohexanediol, a 1:2 mixture of 1,3-cis- and 1,3-trans-cyclohexanediols, and a 1:2 mixture of 1,4-cis- and 1,4-trans-cyclohexanediols. The shape of the emission spectra for the molecules in this series is less sensitive to the viscosity of the medium than was the case for an analogous series in which a methylene or oxyethylene spacer replaces the cyclohexanediol spacer. The dependence of the excimer emission on the type of spacer is different also in the series in which the rigid units contain naphthalene or benzene. When the rigid units contain naphthalene, excimer formation is maximal if the spacer contains 1,2-trans-cyclohexanediol, but this spacer produces a molecule with a very small tendency for excimer formation in its polymers with terephthalate. A conformational analysis correctly concludes that the spacer most conducive to excimer formation should be 1,2-trans-cyclohexanediol, but it does not identify the correct order of the remaining three bichromophoric model compounds. The problem may reside in the method for taking into account the finite width of the torsional well associated with each rotational isomer. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320823
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  • 6
    Electronic Resource
    Electronic Resource
    Intramolecular energy transfer in bichromophoric diesters containing anthracene and naphthalene groups separated by different numbers of methylene spacers (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 3411-3424 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Steady state fluorescence has been used to study the efficiency of nonradiative singlet energy transfer from naphthalene to anthracene in naph-COO—(CH2)m—OOC-anth for m of 2-6. A theoretical analysis has also been performed, using the rotational isomeric state model, of the conformations of these molecules. The experiments clearly demonstrate the presence of nonradiative singlet energy transfer in the bichromophoric compounds, with an efficiency that depends on the solvent and on m. The combination of the experiments and the theoretical analysis establishes that the Förster radius for this system is 1,6 ± 0,2 nm.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021951011
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  • 7
    Electronic Resource
    Electronic Resource
    Identification of volatile compounds resulting from the thermal oxidation of polyethylene (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 1741-1748 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The migration of compounds from polymer-based packaging may impart undesirable odors to foods. We, therefore, undertook a study of the volatile compounds produced during the heating of polyethylene (PE) in the presence of excess O2 at temperatures of 150-350°C and for heating times of 5-15 min. Eightyfour volatile compounds in the range of C5 - C23 were identified by gas chromatography mass spectrometry. The major products were aliphatic hydrocarbons, aldehydes, ketones, and olefins. Changes in temperature and heating times affected the amount and type of compounds produced, with hexanal being found in the largest amount and 300°C resulting in the greatest quantity of volatile compounds. At 350°C, greater amounts and numbers of low-boiling and fewer high-boiling compounds were formed. Only small amounts of volatiles were produced at 150°C. Many of the compounds identified have been reported to have odor and/or toxicological significance. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070471004
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  • 8
    Electronic Resource
    Electronic Resource
    Differential effects of eight metal ions on lymphocyte differentiation antigens in vitro (1990)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 24 (1990), S. 1059-1068 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In vitro studies were conducted to determine the effects of metal ions known to be released from metallic implants in vivo on the expression of lymphocyte surface antigens. Normal human peripheral blood lymphocytes were exposed to various concentrations of metal ions (Fe3+, Ni2+, Co2+, Mo6+, V5+, Cr6+, Cr3+, and Ti3+) for 30 min at 37°C in a 5% CO2 atmosphere, and then analyzed for their ability to form rosettes with sheep red blood cells. Following this preliminary analysis, lymphocytes were exposed to the metal ions found to inhibit the E-rosette reaction (Fe3+, Ni2+, and Co2+) in order to determine which of the following surface antigens were affected: CD2, CD3, CD4, CD8, CD1, CD22, CD10, and HLA-DR. Our results showed that the in vitro treatment of lymphocytes with Fe3+ or Co2+ caused inhibition of CD2 only, whereas Ni2+ caused inhibition of both CD2 and CD3 antigens. These findings suggest that Fe3+, Co2+, and Ni2+ ions may interfere with T cell activation since both CD2 and CD3 are involved in that process.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820240808
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