THE PERMEABILITY OF POTATO TISSUE TO WATER

Abstract

Potato tuber disks such as have been used extensively for water-uptake studies were allowed to take up tritium water, T2O, and their equilibration with H2O was then followed. The T2O in the disks reached equilibrium with the external H2O within about 20 minutes, the time for half the maximum value being about 1.5 minutes. If there was previous exposure to indoleacetic acid, the equilibrium was reached even more rapidly, which is the reverse of what would be pre-dicted if a metabolic water uptake were being promoted. The process is slowed about 50% by cooling to 3[degree]C. The findings are extended and supported by the use of disks of varying thick-nesses. It is concluded that uptake or retention of water by a direct metabolic reaction followed by modification of the cell wall cannot be the mechanism of growth or of auxin action. Hence the auxin action must be exerted directly upon the pro-perties of the cell wall.