Rapid Changes in Permeability of Cell Membranes to Water Brought About by Carbon Dioxide & Oxygen

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Abstract
Influx of water into hypocotyl of Helianthus annus was measured immediately after segments which had first lost approximately 40% of their H2O content by drying in air were placed in water. Efflux of H2O was measured after the segments were transferred from H2O to mannitol solution. Changes in rate of both influx and efflux were interpretable as a measure of changes in the permeability of the cell membranes to H2O. CO2 treatment during the period when influx or efflux was measured markedly reduced both processes within 3 minutes. The inhibition was not due to lack of O2, nor to the lowered pH of the medium. Anaerobiosis also reduced influx within 3 minutes, but to a lesser extent. The effects of treatment for 30 minutes or less with either CO2 or O2-free N2 were fully reversible. Irreversible effects followed longer treatment. Increasing the O2 concentration to 40% increased H2O influx. The presence of O2 in the gas stream also countered to a marked extent the inhibitory effects of CO2. Similar inhibitory effects of CO2 on H2O influx were observed with root tissue of Pisum sativum and Daucus carota.

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