| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1999: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1998: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
1) INVESTIGATION OF SUITABLE CONDITIONS FOR A CREEP VISCOELASTIC ANALYSIS:
The load for deformation and the speed of deformation are primarily important for viscoelastic analysis of extensibility. We found that the load, 20-25 grams/mmィイD12ィエD1, and the speed, 0.5 mm/sec, were suitable for pea roots. The physical viscoelastic parameters were determined by using a Kelvin-Voigt-Bergers model for viscoelastic deformation of root cell walls. The model composed of six elements were applied for the extension of pea roots, which shows relatively high extensibility (Tanimoto et al. Plant and Soil, 200, in press).
2) GIBBERELLIN-MEDIATED CHANGES IN VISCOELASTIC PROPERTIES AND ELONGATION GROWTH :
Effect of gibberellin was investigated on pea roots under the conditions described in the previous section. The cell wall extensibility decreased and the parameters, elastic moduli and viscosity coefficients, increased by the treatment with ancymidol, an inhibitor of gibberellin biosynthesis. This results
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showed that the decline of cell wall extensibility due to ancymidol was caused by the increase in elastic moduli and viscosity coefficients. Gibberellin completely canceled ancymidol-mediated increase in the viscoelastic parameters. This result indicates that gibberellin regulates viscoelastic parameters of root cell walls (a paper manuscript in preparation). Further investigation is in progress on rice and tea plants. We have already confirmed the remarkable effect of gibberellin on the cell wall extensibility in rice leaf sheath (Planta 205, 145-152, 1998). Further investigations on the correlations among these viscoelastic parameters and cell-wall components such as pectins and hemicelluloses and its hydraulic conditions, have been carrying out.
3) ACID GROWTH AND VISCOELASTIC PROPERTIES OF CELL WALLS :
Studies on the correlations between cell wall extension and changes in viscoelastic parameters are important to understand the cell wall extension under the acidic condition. We have found the remarkable decrease in viscosity coefficient (η0) by lowering pH from pH6 to pH3. the value of η0 at pH 3 was 1/3 of the value at pH 6. This drastic decrease in viscosity could be one of the major factors for the acid-induced sliding of polymers in root cell walls, which is at least partially mediated by some proteins like expansion. This finding was accepted for publication (Tanimoto et al. Plant and Soil, 2000 in press). Less
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