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  • 1
    Electronic Resource
    Electronic Resource
    Changes in IAA responsiveness in the elongation region of graviresponding mung bean roots (1996)
    Springer
    Plant growth regulation 20 (1996), S. 245-251 
    Details
    ISSN: 1573-5087
    Keywords: auxin ; IAA ; gravitropism ; sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract IAA responsiveness of sections of root tissue taken from the top and bottom of mung bean roots was assessed prior to and at varying times following gravistimulation. Prior to gravistimulation, root tissue sections from the sides of the elongation zone responded similarly to IAA. After gravistimulation (within 5 min), root sections from the bottom of the elongation zone became more responsive to IAA than sections collected from the upper side of the elongation zone. The change in IAA responsiveness of these tissue sections was transient with root sections from both the top and bottom of the elongation zone again exhibiting similar responsiveness to IAA following 15 minutes of gravistimulation. These studies also examined if the root tip is required for the gravity-induced shift in IAA responsiveness in the tissues of the elongation zone. The IAA responsiveness of top and bottom sections of the elongation zone from decapped mung bean roots was assessed at varying times following gravistimulation. The responsiveness to IAA of top and bottom sections changed rapidly in decapped roots, just as had been previously found for intact roots. Although the alteration in responsiveness was transient in decapped roots (just as intact roots), the time it took for the sections to recover previous responsiveness to IAA was extended. These results suggest that the initial growth response of graviresponding roots may be due to a change in the IAA responsiveness of tissues in the elongation zone and not an asymmetric accumulation of IAA on the lower side of the elongation zone. The results also indicate that the gravity-induced shift in IAA responsiveness in the elongation zone occurs independently of the root cap, suggesting that the cells in the elongation region can perceive and respond to gravity independently of the root cap during the intial phases of the gravity response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00043314
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    Paper (German National Licenses)
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Transport of [3H]IAA label in gravistimulated primary roots of maize (1995)
    Springer
    Plant growth regulation 16 (1995), S. 83-92 
    Details
    ISSN: 1573-5087
    Keywords: auxin ; IAA ; gravitropism ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The curvature of roots in response to gravity is attributed to the development of a differential concentration gradient of IAA in the top and bottom of the elongation region of roots. The development of the IAA gradient has been attributed to the redistribution of IAA from the stele to cortical tissues in the elongation region. The gravistimulated redistribution of IAA was investigated by applying [3H]IAA to the cut surface of 5 mm apical primary root segments. The movement of label from the stele-associated [3H]IAA into the root, tip, root cap, and cortical tissues on the top and bottom of the elongation region was determined in vertically growing roots and gravistimulated roots. Label from the stele moved into the region of cell differentiation (root tip) prior to accumulating in the elongation region. Little label was observed in the root cap. Gravistimulation did not increase the amount of label moving from the stele; but gravistimulation did increase the amount of label accumulating in cortical tissues on the lower side of the elongation region, and decreased the amount of label accumulating in cortical tissues on the upper side of the elongation region. Removal of the cap prior to or immediately following gravity stimulation rendered the roots partially insensitive to gravity and also prevented gravity-induced asymmetric redistribution of label. However, removal of the root cap following 30 min of gravistimulation did not alter root curvature or the establishment of an IAA asymmetry across the region of root elongation. These results suggest that a signal originating in the root cap directs auxin redistribution in tissues behind the root cap, leading to the development of an asymmetry of IAA concentration in the elongation region that in turn causes the differential growth rate in the elongation region of a graviresponding root.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040511
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    Paper (German National Licenses)
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