Reduction in Turgor Pressure as a Result of Extremely Brief Exposure to CO2

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Abstract
CO2 depressed water influx into sunflower hypocotyl segments of low water potential; by contrast, it stimulated flux into segments of high water potential. Flux into CO2-treated segments in a mannitol solution of 3 atm. equalled that into control tissue in water. Direct measurements detected no difference in the steady state value for osmotic pressure as between treated and control tissue. Reasons are given for concluding that CO2 had caused a reduction in turgor pressure. Water uptake into tissue treated with CO2 for only the first 2 minutes of a 30-minute period was equal to that into tissue treated continuously with CO,, i.e. 3 times control value. Ten seconds'' CO2 treatment produced a significant stimulation. Treatment applied in a moist air chamber stimulated subsequent influx when the tissue was transferred to water. The CO2 stimulation was still observed when a transition period of 30 minutes was interposed between treatment and transfer to water. The effect was obtained even when treatment and transition period were at zero degrees.