Relative control potential of abscisic acid, carbon dioxide and light in responses of Phaseolus vulgaris stomata.

We outline a theoretical framework for comparing the relative effectiveness of hormonal and other factors in the control of physiological responses. This involves determining a 'baseline' set of conditions, then adjusting each factor in turn with the others held constant. The initial rate of response to each change in condition is estimated and compared among factors to arrive at a quantitative indication of control potential under the specified baseline conditions - the control coefficient.