A Model for the Interaction of Low Temperature, ABA, IAA, and CO2in the Control of Stomatal Behaviour

Abstract

In the chilling sensitive (C.S.) species Phaseolus vulgaris it was found that at 22 °C ABA induced stomatal closure but this effect was dependent on the presence of CO₂. In the absence of CO₂ the effect of ABA was completely lost. In contrast to ABA, the effect of IAA at 22 °C was to increase stomatal opening as the IAA concentration increased from 10⁻² to 10 mol m⁻³, and this effect was dependent upon the presence of CO₂. However, at 5 °C the action of ABA was reversed and it was found to induce stomatal opening when fed via the transpiration stream in excised leaves. Similarly, the CO₂ response characteristics were reversed at low temperatures as removal of CO₂ from the atmosphere caused stomatal closure. However, the effect of IAA at 5 °C in the presence of CO₂ and with or without ABA was to increase stomatal aperture with increasing IAA concentration. Significantly, ABA was found to have no effect upon aperture in the presence of CO₂ when IAA was added. The interactive effects of ABA, IAA, CO₂ and low temperature are discussed in relation to a model proposed by the authors.