QUANTITATIVE-ANALYSIS OF THE CONTROL OF PHYSIOLOGICAL PHENOMENA BY PLANT HORMONES

We highlight the need to combine information about hormone concentrati ons and tissue sensitivity when assessing control of physiological phe nomena by plant hormones. A quantitative approach to this problem is s uggested and the method illustrated using data for stomatal closure in duced by abscisic acid. The technique requires accurate estimates of h ormone concentration at the putative site of action and information ab out the kinetics of responses in the form of dose-response curves obta ined under relevant conditions. Extending this approach, hormonal cont rol is seen as relative, in that it must be considered against a backg round of other controlling influences. Possible means of evaluating th is 'control potential' from dose-response curves are discussed. Finall y, we draw together the above in an analytical framework for assessing hormonal control. This involves (1) matching observed and predicted r esponses; (2) studying effects of manipulating hormone concentration o r sensitivity; and (3) assessing the relative control potential of the compound of interest.