Internodal Elongation and Ethylene Concentration of Floating Rice Stem Sections Submerged at Different Water Depths

Internodal elongation and endogenous ethylene concentration were analysed in floating or deep water rice stem sections submerged at different water depths. The elongation rate of the internodes was independent of the water depth. Elongation rate and ethylene concentration of the internodes were high in the stem sections submerged completely in water, but they decreased when parts of the stem sections were above the water surface. In the stem sections previously submerged, in which the ethylene levels were high , internodal elongation continued after parts of the sections were exposed to ambient air even though the ethylene levels decreased. These results suggest that internodal elongation is independent of the water pressure and that the different concentrations of internodal ethylene partially reflect the difference in the diffusion rate of ethylene in water. They also suggest that ethylene acts as a trigger of internodal elongation.