Quantitative analysis of the control of physiological phenomena by plant hormones

Abstract

We highlight the need to combine information about hormone concentrations and tissue sensitivity when assessing control of physiological phenomena by plant hormones. A quantitative approach to this problem is suggested and the method illustrated using data for stomatal closure induced by abscisic acid. The technique requires accurate estimates of hormone concentration at the putative site of action and information about the kinetics of responses in the form of dose‐response curves obtained under relevant conditions. Extending this approach, hormonal control is seen as relative, in that it must be considered against a background of other controlling influences. Possible means of evaluating this ‘control potential’ from dose‐response curves are discussed. Finally, we draw together the above in an analytical framework for assessing hormonal control. This involves (1) matching observed and predicted responses; (2) studying effects of manipulating hormone concentration or sensitivity; and (3) assessing the relative control potential of the compound of interest.