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  • 11
    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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  • 12
    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/BF00552667
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  • 13
    Electronic Resource
    Electronic Resource
    Correlations between proton-efflux patterns and growth patterns during geotropism and phototropism in maize and sunflower (1981)
    Springer
    Planta 152 (1981), S. 239-241 
    Details
    ISSN: 1432-2048
    Keywords: Acid growth ; Geotropism ; Helianthus ; Phototropism ; Proton secretion ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By placing seedlings of sunflower (Helianthus annuus L.) or maize (Zea mays L.) on agar plates containing a pH indicator dye it is possible to observe surface pH patterns along the growing seedling by observing color changes of the indicator dye. Using this method we find that in geotropically stimulated sunflower hypocotyls or maize coleoptiles there is enhanced proton efflux on the lower surface of the organ prior to the initiation of curvature. As curvature develops the pattern of differential acid efflux becomes more intense. A similar phenomenon is observed when these organs are exposed to unilateral illumination, i.e. enhanced acid efflux occurs on the dark side of the organ prior to the initiation of phototropic curvature and the pattern of differential acid efflux intensifies as phototropic curvature develops. These observations indicate that differential acid efflux occurs in response to tropistic stimuli and that the acid efflux pattern may mediate the development of tropistic curvatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385150
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  • 14
    Electronic Resource
    Electronic Resource
    Binding of 45Ca2+ to particulate fractions of coleoptile tissue (1976)
    Springer
    Planta 130 (1976), S. 295-301 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using recently developed techniques, we have investigated the binding of 45Ca2+ to membrane preparations from corn (Zea mays L) and oat (Avena sativa L) coleoptile tissue. Scatchard plot analysis reveals at least two Ca2+-binding sites in each tissue, a high affinity binding site (K m=7.7×10-7 M, n=6.9×10-10 mol·0.5 g f.w.-1 in corn, K m=4.93×10-6 M, n=2.29×10-9 mol·0.5 g f.w.-1 in Avena) and a low affinity binding site (K m=9.01×10-5 M, n=5.4×10-8 mol·0.5 g f.w.-1 in corn; K m=1.03×10-4 M, n=3.40×10-8 mol·0.5 g f.w.-1 in Avena). There is also some evidence of a third, lower affinity binding site in each tissue, especially corn. More detailed studies with corn coleoptile homogenates show that they contain a potent dialyzable inhibitor of Ca2+ binding. Monovalent cations were observed to be ineffective as inhibitors of Ca2+ binding in corn. However, of six divalent cations tested, all were capable of strong inhibition of Ca2+-binding and there appeared to be a relationship between size of the atomic radius of the ion and potency as an inhibitor of calcium binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387836
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  • 15
    Electronic Resource
    Electronic Resource
    Cellular sequence of tracheal repair in sheep after smoke inhalation injury (1992)
    Springer
    Lung 170 (1992), S. 331-338 
    Details
    ISSN: 1432-1750
    Keywords: Tracheal epithelium ; Cell regeneration ; Basal cells ; Ciliated cells ; Toxic smoke injury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The cellular repair process of injured tracheal epithelium is described for sheep after exposure to toxic smoke containing high concentrations of acrolein. Fourteen fasted 3–4-year-old ewes had a portion of their cervical trachea exposed to cotton smoke for 20 min and then were sacrificed at various time intervals ranging from 1 to 22 days after exposure. Within 1 day of injury, columnar epithelium sloughed intact from the trachea with a concomitant reduction of nearly 35% in the basal cell population. At 2 days of recovery, the cellularity of the epithelium had increased and mitotic figures were observed in some tracheal epithelial and gland cells. By 8 days, undifferentiated hyperplastic cells increased to 30/100 µm, differentiated nonciliated columnar cells first appeared, and the basal cell population returned to a normal count of 13 cells/100µm. Thirteen days after exposure, the undifferentiated hyperplastic cell population had declined to 7 cells/100/ µm, nonciliated columnar cells were at control values, and some ciliated cells were identified. At 18 and 22 days, epithelium was normal in appearance and the count was 13 cells/100µm. Data suggest that because the columnar epithelium sloughs intact with the cilia remaining active, toxic smoke may affect their attachment to the basal lamina. Furthermore, the regeneration process involves differentiation of hyperplastic cells in which they elongate down to the basal lamina, thus re-establishing the integrity of tall, epithelium in the sheep trachea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00177579
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  • 16
    Electronic Resource
    Electronic Resource
    Growth factors accelerate epithelial repair in sheep trachea (1993)
    Springer
    Lung 171 (1993), S. 335-344 
    Details
    ISSN: 1432-1750
    Keywords: Epidermal growth factor ; Platelet derived growth factor ; Inhalation injury ; Tracheal repair process
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Toxic gases and fumes have been shown to be injurious to the upper airways. Repair of this injury involves proliferation and migration of surviving nonciliated cells, followed by differentiation to a normal phenotype. Because recent results suggested that growth factors could improve the outcome of an airway injury, we undertook this study to determine the efficacy of these materials as an initial treatment to accelerate the healing process. In 24 anesthetized sheep, a portion of the trachea was exposed to smoke from smouldering cotton cooled to 37°C. Twelve received aerosolized epidermal growth factor plus platelet derived growth factor, while twelve received placebo. At 10 days after injury, nonciliated and ciliated cells were totally absent in the injured trachea receiving the placebo. In animals receiving growth factors, nonciliated and ciliated cells, however, were present (56% and 31% of uninjured trachea, respectively). At 13 days after injury, nonciliated and ciliated cell counts in those receiving placebo were 67% and 33% of uninjured, respectively. In sheep receiving growth factors, tracheal nonciliated and ciliated cell counts had increased to 105% and 64% of uninjured trachea, respectively. We conclude that growth factors therapy after airway injury stimulates cell proliferation and differentiation, and this therapeutic intervention to accelerate the repair process in acute airway injury is an approach applicable to humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165699
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  • 17
    Electronic Resource
    Electronic Resource
    Computer-based video digitizer analysis of surface extension in maize roots (1991)
    Springer
    Planta 183 (1991), S. 381-390 
    Details
    ISSN: 1432-2048
    Keywords: Digitizer ; Gravitropism (root, digitizer analysis) ; Growth (root) ; Root (gravitropism, growth) ; Zea (root gravitropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We used a video digitizer system to measure surface extension and curvature in gravistimulated primary roots of maize (Zea mays L.). Downward curvature began about 25 ± 7 min after gravistimulation and resulted from a combination of enhanced growth along the upper surface and reduced growth along the lower surface relative to growth in vertically oriented controls. The roots curved at a rate of 1.4 ± 0.5° · min−1 but the pattern of curvature varied somewhat. In about 35% of the samples the roots curved steadily downward and the rate of curvature slowed as the root neared 90°. A final angle of about 90° was reached 110 ±35 min after the start of gravistimulation. In about 65% of the samples there was a period of backward curvature (partial reversal of curvature) during the response. In some cases (about 15% of those showing a period of reverse bending) this period of backward curvature occurred before the root reached 90°. Following transient backward curvature, downward curvature resumed and the root approached a final angle of about 90°. In about 65% of the roots showing a period of reverse curvature, the roots curved steadily past the vertical, reaching maximum curvature about 205 ± 65 min after gravistimulation. The direction of curvature then reversed back toward the vertical. After one or two oscillations about the vertical the roots obtained a vertical orientation and the distribution of growth within the root tip became the same as that prior to gravistimulation. The period of transient backward curvature coincided with and was evidently caused by enhancement of growth along the concave and inhibition of growth along the convex side of the curve, a pattern opposite to that prevailing in the earlier stages of downward curvature. There were periods during the gravitropic response when the normally unimodal growth-rate distribution within the elongation zone became bimodal with two peaks of rapid elongation separated by a region of reduced elongation rate. This occurred at different times on the convex and concave sides of the graviresponding root. During the period of steady downward curvature the elongation zone along the convex side extended farther toward the tip than in the vertical control. During the period of reduced rate of curvature, the zone of elongation extended farther toward the tip along the concave side of the root. The data show that the gravitropic response pattern varies with time and involves changes in localized elongation rates as well as changes in the length and position of the elongation zone. Models of root gravitropic curvature based on simple unimodal inhibition of growth along the lower side cannot account for these complex growth patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197737
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  • 18
    Electronic Resource
    Electronic Resource
    The pH profile for acid-induced elongation of coleoptile and epicotyl sections is consistent with the acid-growth theory (1991)
    Springer
    Planta 186 (1991), S. 70-74 
    Details
    ISSN: 1432-2048
    Keywords: Acid-extension ; Acid-growth theory ; Avena (acid-growth) ; Elongation growth ; pH profile (cell elongation) ; Pisum (acid-growth) ; Zea (acid-growth)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The acid-growth theory predicts that a solution with a pH identical to that of the apoplast of auxintreated tissues (4.5–5.0) should induce elongation at a rate comparable to that of auxin. Different pH profiles for elongation have been obtained, however, depending on the type of pretreatment between harvest of the sections and the start of the pH-incubations. To determine the acid sensitivity under in vivo conditions, oat (Avena sativa L.) coleoptile, maize (Zea mays L.) coleoptile and pea (Pisum sativum L.) epicotyl sections were abraded so that exogenous buffers could penetrate the free space, and placed in buffered solutions of pH 3.5–6.5 without any preincubation. The extension, without auxin, was measured over the first 3 h. Experiments conducted in three laboratories produced similar results. For all three species, sections placed in buffer without pretreatment elongated at least threefold faster at pH 5.0 than at 6.0 or 6.5, and the rate elongation at pH 5.0 was comparable to that induced by auxin. Pretreatment of abraded sections with pH-6.5 buffer or distilled water adjusted to pH 6.5 or above gave similar results. We conclude that the pH present in the apoplast of auxin-treated coleoptile and stems is sufficiently low to account for the initial growth response to auxin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201499
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  • 19
    Electronic Resource
    Electronic Resource
    Cellular specificity of the gravitropic motor response in roots (1997)
    Springer
    Planta 203 (1997), S. S115 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Arabidopsis ; Auxin ; Calcium ; Distal elongation zone ; Gravitropism (root) ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. A number of features of the gravitropic response of roots are not readily accounted for by the classical Cholodny-Went theory. These include the observations that (i) in the later stages of the response the growth gradient is reversed with no evident reversal of the auxin gradient; (ii) a major component of the acceleration of growth along the upper side occurs in the distal elongation zone (DEZ), a group of cells located between the meristem and the main elongation, not within the central elongation zone; and (iii) the initiation of differential growth in the DEZ appears to be independent of the establishment of auxin asymmetry. Alternative candidates for mediation of differential growth in the DEZ include calcium ions and protons. Gravi-induced curvature is accompanied by polar movement of calcium toward the lower side of the maize root tip and the DEZ is shown to be particularly sensitive to growth inhibition by calcium. Also, gravistimulation of maize roots causes enhanced acid efflux from the upper side of the DEZ. Evidence for gravi-induced modification of ion movements in the root tip includes changes in intracellular potentials and current flow. It is clear that there is more than one motor region in the root with regard to gravitropic responses and there is evidence that the DEZ itself consists of more than one class of responding cells. In order to gain a more complete understanding of the mechanism of gravitropic curvature, the physiological properties of the sub-zones of the root apex need to be thoroughly characterized with regard to their sensitivity to hormones, calcium, acid pH and electrical perturbations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008099
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  • 20
    Electronic Resource
    Electronic Resource
    Microsurgical removal of epidermal and cortical cells: evidence that the gravitropic signal moves through the outer cell layers in primary roots of maize (1990)
    Springer
    Planta 180 (1990), S. 530-536 
    Details
    ISSN: 1432-2048
    Keywords: Auxin and gravitropism ; Gravitropism (signal transmission ; Root (gravitropism) ; Zea (gravitropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is general agreement that during root gravitropism some sort of growth-modifying signal moves from the cap to the elongation zone and that this signal ultimately induces the curvature that leads to reorientation of the root. However, there is disagreement regarding both the nature of the signal and the pathway of its movement from the root cap to the elongation zone. We examined the pathway of movement by testing gravitropism in primary roots of maize (Zea mays L.) from which narrow (0.5 mm) rings of epidermal and cortical tissue were surgically removed from various positions within the elongation zone. When roots were girdled in the apical part of the elongation zone gravitropic curvature occurred apical to the girdle but not basal to the girdle. Filling the girdle with agar allowed curvature basal to the girdle to occur. Shallow girdles, in which only two or three cell layers (epidermis plus one or two cortical cell layers) were removed, prevented or greatly delayed gravitropic curvature basal to the girdle. The results indicate that the gravitropic signal moves basipetally through the outermost cell layers, perhaps through the epidermis itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411451
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