Permeability of Avena Coleoptile Sections to Water Measured by Diffusion of Deuterium Hydroxide.

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Abstract
Indoleacetic acid in optimal concentration has no effect on the diffusion of deuterium hydroxide solutions into Avena coleoptile sections. The half-time of DHO diffusion into sections is 8 to 10 minutes. The inward and outward diffusion curves are identical in shape and half-times. The state of turgor has no influence on the water permeability of this tissue. Inhibitors such as 2,4-DNP and KCN in non-lethal concentrations have only slight, if any, effect on permeability. Killing of the tissue results in a very slight increase in permeability. The smallness of the increase indicates that the cell wall rather than the cell membranes is the primary barrier to water movement. Determination of tissue permeability by osmotic means yields rates of water movement essentially identical to those obtained by the isotopic method. The half-time of protoplast expansion or contraction of individual cells located near the surface is however 2 to 3 minutes and in cases in which the cells are very near to cut tissue edges, 1 minute or less. Cell permeability of Avena coleoptile section tissue is thus greater than the permeability of the tissue as a whole.

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