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  • 1
    Electronic Resource
    Electronic Resource
    Adaptation of corn roots to exogenously applied auxin (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 51 (1981), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The ability of intact primary roots of corn (Zea mays L. Bear Hybrid WF 9 × 38) to adapt to growth-inhibitory concentrations of auxin was studied using a highly sensitive position sensor transducer to measure growth. The timing, concentration dependence and temperature dependence of adaptation were studied as well as the time course of loss of adaptation upon removal of auxin. The rate of root elongation is inhibited 80% within 40 min after application of 10−7M IAA. Within 90 min growth rate begins to recover. For concentrations of IAA equal to or greater than 10−7M, recovery of growth rate (adaptation) is incomplete. Corn roots show a similar pattern of adaptation to the synthetic auxins NAA and 2,4-D. The Q10 for adaptation is high (3.2) and comparable to that for root growth (3.3). Upon removal of exogenous IAA, loss of adaptation occurs with full sensitivity to the hormone regained within 20 min.Based on the auxin specificity and the Q10 for adaptation it is concluded that adaptation occurs neither by a change in the auxin degradation capacity of the root nor by a diffusional redistribution of applied auxin. It is suggested that adaptation involves metabolic processes, perhaps a metabolically dependent alteration of the number or affinity of auxin binding sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1981.tb05575.x
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  • 2
    Electronic Resource
    Electronic Resource
    Calcium ion dependency of ethylene production in segments of primary roots of Zea mays (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 67 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We investigated the effect of Ca2+ on ethylene production in 2-cm long apical segments from primary roots of corn (Zea mays L., B73 × Missouri 17) seedlings. The seedlings were raised under different conditions of Ca2+ availability. Low-Ca and high-Ca seedlings were raised by soaking the grains and watering the seedlings with distilled water or 10 mM CaCl2, respectively. Segments from high-Ca roots produced more than twice as much ethylene as segments from low-Ca roots. Indoleacetic acid (IAA; 1 μM) enhanced ethylene production in segments from both low-Ca and high-Ca roots but auxin-induced promotion of ethylene production was consistently higher in segments from high-Ca roots. Addition of I-aminocyclopropane-I-carboxylic acid (ACC) to root segments from low-Ca seedlings doubled total ethylene production and the rate of production remained fairly constant during a 24 h period of monitoring. In segments from high-Ca seedlings ACC also increased total ethylene production but most of the ethylene was produced within the first 6 h. The data suggest that Ca2+ enhances the conversion of ACC to ethylene. The terminal 2 mm of the root tip were found to be especially important to ethylene biosynthesis by apical segments and, experiments using 45Ca2+ as tracer indicated that the apical 2 mm of the root is the region of strongest Ca2+ accumulation. Other cations such as Mn2+, Mg2+, and K+ could largely substitute for Ca2+. The significance of these findings is discussed with respect to recent evidence for gravity-induced Ca2+ redistribution and its relationship to the establishment of asymmetric growth during gravitropic curvature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb05057.x
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of calcium and pH on growth in primary roots of Zea mays (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 72 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Hasenstein, K. H. and Evans, M. L. 1988. The influence of calcium and pH on growth in primary roots of Zea mays. - Physiol. Plant. 72: 466–470.We investigated the interaction of Ca2+ and pH on root elongation in Zea mays L. cv. B73 × Missouri 17 and cv. Merit. Seedlings were raised to contain high levels of Ca2+ (HC, imbibed and raised in 10 mM CaCl2) or low levels of Ca2+ (LC, imbibed and raised in distilled water). In HC roots, lowering the pH (5 mM MES/Tris) from 6.5 to 4.5 resulted in strong, long-lasting growth promotion. Surprisingly, increasing the pH from 6.5 to 8.5 also resulted in strong growth promotion. In LC roots acidification of the medium (pH 6.5 to 4.5) resulted in transient growth stimulation followed by a gradual decline in the growth rate toward zero. Exposure of LC roots to high pH (pH shift from 6.5 to 8.5) also promoted growth. Addition of EGTA resulted in strong growth promotion in both LC and HC roots. The ability of EGTA to stimulate growth appeared not to be related to H+ release from EGTA upon Ca2+ chelation since, 1) LC roots showed a strong and prolonged response to EGTA, but only a transient response to acid pH, and 2) promotion of growth by EGTA was observed in strongly buffered solutions. We also examined the pH dependence of the release of 45Ca2+ from roots of 3-day-old seedlings grown from grains imbibed in 45Ca2+. Release of 45Ca2+ from the root into agar blocks placed on the root surface was greater the more acidic the pH of the blocks. The results indicate that Ca2+ may be necessary for the acid growth response in roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb09152.x
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of growth patterns during gravitropic curvature in roots ofZea mays by use of a computer-based video digitizer (1986)
    Springer
    Journal of plant growth regulation 5 (1986), S. 73-83 
    Details
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A computer-based video digitizer system is described which allows automated tracking of markers placed on a plant surface. The system uses customized software to calculate relative growth rates at selected positions along the plant surface and to determine rates of gravitropic curvature based on the changing pattern of distribution of the surface markers. The system was used to study the time course of gravitropic curvature and changes in relative growth rate along the upper and lower surface of horizontally-oriented roots of maize (Zea mays L.). The growing region of the root was found to extend from about 1 mm behind the tip to approximately 6 mm behind the tip. In vertically-oriented roots the relative growth rate was maximal at about 2.5 mm behind the tip and declined smoothly on either side of the maximum. Curvature was initiated approximately 30 min after horizontal orientation with maximal (50°) curvature being attained in 3 h. Analysis of surface extension patterns during the response indicated that curvature results from a reduction in growth rate along both the upper and lower surfaces with stronger reduction along the lower surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02025958
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  • 5
    Electronic Resource
    Electronic Resource
    Auxin action on proton influx in corn roots and its correlation with growth (1980)
    Springer
    Planta 148 (1980), S. 510-512 
    Details
    ISSN: 1432-2048
    Keywords: Auxin ; Cell wall pH ; Growth (roots) ; Proton flux and growth ; Root growth ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract At concentrations inhibitory to the elongation of corn (Zea mays L.) roots, the auxins, indole-3-acetic acid (IAA) and α-naphthaleneacetic acid (α-NAA), cause an increase in the pH of the bathing medium; this increase occurs with an average latent period shorter than the latent period for the inhibitory effect of these auxins on elongation. Indole-2-carboxylic acid, an inactive structural analogue of IAA, and β-naphthaleneacetic acid, an inactive analogue of α-NAA, affect neither growth nor the pH of the medium. Since acid pH is known to promote and basic pH to inhibit root elongation, the data are consistent with the hypothesis that hormone-induced modification of cell-wall pH plays a role in the control of elongation of roots, as has been proposed for elongation of stems and coleoptiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395322
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  • 6
    Electronic Resource
    Electronic Resource
    Inhibition of polar calcium movement and gravitropism in roots treated with auxin-transport inhibitors (1984)
    Springer
    Planta 160 (1984), S. 536-543 
    Details
    ISSN: 1432-2048
    Keywords: Allium ; Calcium and gravitropism ; Morphactin ; Naphthylphthalamic acid ; Pisum (gravitropism) ; 2,3,5-Triiodobenzoic acid ; Zea (gravitropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Primary roots of maize (Zea mays L.) and pea (Pisum sativum L.) exhibit strong positive gravitropism. In both species, gravistimulation induces polar movement of calcium across the root tip from the upper side to the lower side. Roots of onion (Allium cepa L.) are not responsive to gravity and gravistimulation induces little or no polar movement of calcium across the root tip. Treatment of maize or pea roots with inhibitors of auxin transport (morphactin, naphthylphthalamic acid, 2,3,5-triiodobenzoic acid) prevents both gravitropism and gravity-induced polar movement of calcium across the root tip. The results indicate that calcium movement and auxin movement are closely linked in roots and that gravity-induced redistribution of calcium across the root cap may play an important role in the development of gravitropic curvature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411142
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  • 7
    Electronic Resource
    Electronic Resource
    The kinetics of abscisic acid action on root growth and gravitropism (1983)
    Springer
    Planta 157 (1983), S. 150-157 
    Details
    ISSN: 1432-2048
    Keywords: Abscisic acid and root growth ; Acid efflux and root growth ; Aminoethoxyvinylglycine ; Gravitropism (root) ; Phaseic acid ; Pisum (root growth) ; Root growth (hormones) ; Zea (root growth)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using an auxanometer and time-lapse cinematography we have studied the timing of abscisic acid (ABA) effects on elongation, gravitropic curvature, and hydrogen-ion efflux in several cultivars of maize (Zea mays L.). The effect of high concentrations (e.g. 0.1 mM) of ABA on root elongation is triphasic, including 1) a period of promotion lasting approximately 12 h, 2) a subsequent period of increasing inhibition lasting approximately 12h, and 3) gradual recovery to a rate within approximately 80% of the control rate. With lower concentrations of ABA (e.g. 0.1 μM) only the transient promotive phase is seen. Abscisic acid enhances ethylene biosynthesis in roots of maize but suppression of ethylene biosynthesis does not prevent the long-term inhibitory action of ABA on growth. Application of ABA (0.1 mM) to the upper surface of horizontally placed roots accelerates positive gravitropism. Application of ABA to the lower surface retards gravitropism and in some cases causes the roots to curve upward against the direction of gravity. These observations are consistent with our finding that the initial effect of ABA on root elongation is stimulatory. Since root gravitropism is rapid enough to be completed within the stimulatory phase of ABA action, the data argue against hypotheses of gravitropism based upon accumulation of ABA to inhibitory levels on the lower side of a hirizontal root.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393649
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  • 8
    Electronic Resource
    Electronic Resource
    Responses ofArabidopsis roots to auxin studied with high temporal resolution: Comparison of wild type and auxin-response mutants (1994)
    Springer
    Planta 194 (1994), S. 215-222 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis (mutants) ; Auxin ; Growth (root, auxin) ; Mutant (Arabidopsis) ; Root elongation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We modified a video digitizer system to allow short-term high-resolution measurements of root elongation in intact seedlings ofArabidopsis thaliana (L.) Heynh. We used the system to measure the kinetics of promotion and inhibition of root elongation by applied auxin and to determine the dose-response relationship for auxin action on elongation in roots of wild-type seedlings and seedlings of mutants (axr1,aux1, andaxr2) with altered auxin responsiveness. Roots of the mutants showed less inhibition in the presence of inhibitory concentrations of auxin than did roots of the wild type. The latent period preceding the change in elongation rate after auxin application was the same foraxr1 andaxr2 as for the wild type whereas the latent period foraux1 was about twice as long as for the wild type. Low concentrations (ca. 10−11 M) of auxin induced substantial promotion of root elongation in the wild type and inaxr2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01101680
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  • 9
    Electronic Resource
    Electronic Resource
    Responses of Arabidopsis roots to auxin studied with high temporal resolution: Comparison of wild type and auxin-response mutants (1994)
    Springer
    Planta 194 (1994), S. 215-222 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis (mutants) ; Auxin ; Growth (root, auxin) ; Mutant (Arabidopsis) ; Root elongation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We modified a video digitizer system to allow short-term high-resolution measurements of root elongation in intact seedlings of Arabidopsis thaliana (L.) Heynh. We used the system to measure the kinetics of promotion and inhibition of root elongation by applied auxin and to determine the dose-response relationship for auxin action on elongation in roots of wild-type seedlings and seedlings of mutants (axr1, aux1, and axr2) with altered auxin responsiveness. Roots of the mutants showed less inhibition in the presence of inhibitory concentrations of auxin than did roots of the wild type. The latent period preceding the change in elongation rate after auxin application was the same for axr1 and axr2 as for the wild type whereas the latent period for aux1 was about twice as long as for the wild type. Low concentrations (ca. 10−11 M) of auxin induced substantial promotion of root elongation in the wild type and in axr2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196390
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  • 10
    Electronic Resource
    Electronic Resource
    Auxin inhibition of acid-and fusicoccin-induced elongation in lentil roots (1977)
    Springer
    Planta 136 (1977), S. 97-102 
    Details
    ISSN: 1432-2048
    Keywords: Acid growth ; Auxin ; Ethylene ; Fusicoccin ; Growth inhibition ; Lens ; Root growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Both acid pH (4.0) and fusicoccin (FC) strongly stimulate root elongation in intact lentil (Lens culinaris Med.) seedlings. FC-induced elongation is apparently mediated by FC-enhanced H+ secretion since the toxin induces massive secretion of H+ in these roots after a latent period of less than 5 min. Auxin (indole-3-acetic acid) strongly inhibits elongation in control roots as well as acid-induced and FC-induced root elongation. Treatment of apical root segments with auxin causes only a slight apparent uptake of H+ and has no inhibitory effect on FC-induced H+ secretion, whether the hormone is given before or after the toxin. Auxin induces ethylene production in excised roots of lentil but the latent period is at least 30 min while inhibition of root elongation by IAA is maximal within 30 min. It is concluded that the inhibitory action of auxin on acid-and fusicoccin-induced root elongation is a direct effect, independent of auxin-induced ethylene production or auxin-mediated modification of cell-wall pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396184
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