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  • 1
    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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  • 2
    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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