Evidence for a CO2Inhibited Proton Extrusion Pump in the Stomatal Cells ofTradescantia virginiana

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Abstract
The effect of CO2 on the electrical potential difference (p.d.) of the cells of the stomatal complex of Tradescantia virginiana has been investigated. Enhanced levels of CO2 affected all the cells equally by depolarizing the p.d. On removal of the CO2 there was an immediate hyperpolarization, the degree of which was linearly related to the length of time the CO2 was given. Changes in the pH of the cytoplasm and the vacuolar sap were observed during and after treatment with CO2. The metabolic inhibitor 2,4-DNP eliminated the effect of CO2 on the p.d. These results wuld be explained by postulating an electrogenic proton pump in the plasmalemma which is inhibited by CO2.