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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Spectroscopic studies of the manganese complex of Photosystem II (1993)
    Springer
    Photosynthesis research 38 (1993), S. 341-346 
    Details
    ISSN: 1573-5079
    Keywords: oxygen evolving complex (OEC) ; EPR ; EXAFS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Our recent EPR and EXAFS experiments investigating the structure of the oxygen-evolving complex of PS II are discussed. PS II treatments which affect the cofactors calcium and chloride have been used to poise samples in modified forms of the S-states, S1, S2 and S3. X-ray absorption studies indicate a similar overall structure for the manganese complex between treated and native samples although the influence of the treatments and cofactors is observed. Manganese oxidation (or oxidation of a ligand to the manganese cluster) is indicated to occur on each of the transitions S1 →S2 and S2 →S3 in these modified samples. The cluster appears to contain at least two inequivalent Mn-Mn pairs. In the native samples the Mn-Mn distance is 2.7 Å, but in samples where the calcium site is affected, one of the pairs has a 3.0 Å Mn-Mn distance. The intensity of the 3.3/3.6 Å interaction is reduced on sodium chloride treatment (calcium depletion) perhaps indicating calcium binding close to the manganese cluster. From EPR data we also propose that treatments which affect calcium and chloride binding cause a modification of the native S2 state, slow the reduction of Yz • and allow an S3 EPR signal to be observed following illumination. The origin of the S3 EPR signal, a modified S3 or S2 X• where X• is an organic radical of unknown charge, is discussed in relation to the results from the EXAFS studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046759
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of calmodulin antagonists on the growth and graviresponsiveness of primary roots of maize (1992)
    Springer
    Plant growth regulation 11 (1992), S. 419-427 
    Details
    ISSN: 1573-5087
    Keywords: Calmodulin ; gravitropism ; growth ; calcium ; auxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We examined the effect of calmodulin (CaM) antagonists applied at the root tip on root growth, gravity-induced root curvature, and the movement of calcium across the root tip and auxin (IAA) across the elongation zone of gravistimulated roots. All of the CaM antagonists used in these studies delayed gravity-induced curvature at a concentration (1 μM) that did not affect root growth. Calmodulin antagonists (≧ 1μM) inhibited downward transport of label from 45Ca2+ across the caps of gravistimulated roots relative to the downward transport of 45Ca2+ in gravistimulated roots which were not treated with CaM antagonists. Application of CaM antagonists at the root tip (≧ 1μM) also decreased the relative downward movement of label from 3H-IAA applied to the upper side of the elongation zone of gravistimulated roots. In general, tip application of antagonists inhibited neither the upward transport of 45Ca2+ in the root tip nor the upward movement of label from 3H-IAA in the elongation zone of gravistimulated roots. Thus, roots treated with CaM antagonists (≧ 1 μM) become less graviresponsive and exhibit reduced or even a reversal of downward polarity of calcium transport across the root tip and IAA transport across the elongation zone. The results indicate that calmodulin-regulated events play a role in root gravitropism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00130651
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  • 10
    Electronic Resource
    Electronic Resource
    Calcium-dependent asymmetric movement of 3H-indole-3-acetic acid across gravistimulated isolated root caps of maize (1994)
    Springer
    Plant growth regulation 14 (1994), S. 235-242 
    Details
    ISSN: 1573-5087
    Keywords: auxin transport ; calcium ; gravitropism ; root cap ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract There is evidence that the cap is the initial site of lateral auxin redistribution during the gravitropic response of roots. We tested this further by comparing asymmetric auxin redistribution across the tips of gravistimulated intact roots, decapped roots, isolated root caps and isolated apical sections taken from decapped roots. Gravistimulation caused asymmetric (downward) auxin movement across the tips of intact roots and isolated root caps but not across the tips of decapped roots or across isolated apical root segments. Naphthylphthalamic acid and pyrenoylbenzoic acid, inhibitors of polar auxin transport, inhibited asymmetric auxin redistribution across gravistimulated isolated root caps and across the tips of gravistimulated intact roots. For intact roots there was a positive correlation between the extent of inhibition of assymmetric auxin redistribution by polar auxin transport inhibitors and the extent of inhibition of asymmetric calcium chelating agent, ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid, also caused parallel inhibition of asymmetric auxin redistribution and gravitropic curvature and this effect was reversed by subsequent treatment with calcium. The results support the hypothesis that the cap is a site of early development of auxin asymmetry in gravistimulated roots and that calcium plays an important role in the development of lateral auxin redistribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024798
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