Gibberellic Acid-Induced Alpha -Amylase Synthesis in Wheat Aleurone Layers: a Distinction Between Site Saturation and Lag Times.

Abstract

We have examined a number of parameters relating to the gibberellic acid (GA₃) requirement for the induction process which leads to the formation of ±-amylase in wheat aleurone tissue. (1) Over a wide range of hormone concentrations, aleurone tissue was found to produce less ±-amylase after hormone withdrawal by washing at a time soon after GA*3 application. (2) The approximate length of this washing-sensitive period was found to vary inversely to the applied GA*3 concentration. (3) Following this early period, a time was found when the response could not be lowered by this same washing procedure which had earlier lowered the response. (4) Separate experiments determined that these results could not be accounted for by variation in the lag/latent period, since the lag period was about the same for a wide range of GA*3 concentrations. To help explain these results we have suggested the term 'site saturation time' which is separate from but intimately involved with the lagllatent period. This term is defined as the time required for the saturation and activation of all sites which ultimately lead to the production of ±-amylase. It is suggested that site saturation time must be taken into account when the early events of ±-amylase induction are examined.