Regulation of Elongation Growth of Excised segments of Vigna Hypocotyl under Osmotic Stress in the Absence or Presence of Absorbable Solute

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The regulation of elongation growth in excised segments of Vigna hypocotyl under osmotic stress was investigated by means of the xylem perfusion and pressure-jump method. When subjected to osmotic stress in the absence of absorbable solutes (100 mM sorbitol only) or in the presence of absorbable solutes (70 mM sorbitol plus 30 mM sucrose, or 70 mM sorbitol plus 15 mM KCl), the hypocotyl segments immediately began to shrink. The hyper-polarizations of the transmembrane potentials (V_<px> and V_<ps>) took place at once. Within 40-60 minutes, the segments resumed growth. In the presence of absorbable solute, there was an obvious increase in the effective turgor (P^i-Y'), but the physiological wall extensibility (φ) increased only slightly. Conversely, in the absence of absorbable solute, φ increased significantly but (P^i-Y') decreased. The results suggest that the recovery of growth of an excised segment under osmotic stress is mainly due to the change in φ in the absence of absorbable solute, and to the change in (P^i-Y') in the presence of absorbable solute, and that the two respiration-dependent proton pumps play important roles in these recovery processes.
日本植物生理学会の論文