Kinetin and Gibberellin Actions on Abscission Processes

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Abstract
An analysis of the effects of kinetin and gibberellin (GAg) on leaf abscission of Phaseolus vulgar is was made in relation to their participation in the 2 separate stages of abscission. Kinetin and gibberellin showed contrasting effects on abscission of bean explants. Kinetin showed a 2 -phase curve like auxin with some promotion at low concentration and inhibition at higher concentrations. Gibberellin promoted abscission at all the concentrations tried. The kinetin inhibition of abscission appears to be a retarding effect on the 1st stage of abscission, since it becomes progressively less with longer induction periods. Conversely, its promotive effect appears to be on the 2nd stage. The gibberellin promotion appears to be an action on the 1st stage, as it is effective at once on young explants. When applied to the intact leaf, kinetin can apparently prolong the 1st stage, deferring the onset of the 2nd stage. Gibberellin application, on the other hand, seems to cause a shortening of the 1st stage and earlier onset of the 2nd stage of abscission.