Influence of ethylene on cytokinin metabolism in relation to Petunia corolla senescence

Exogenous ethylene induced, and cytokinin suppressed, Petunia corolla senescence. 6-Benzylaminopurine and zeatin riboside, the principal cytokinin in corollas at the time of corolla opening, were effective senescence retardants but O-glucosyldihydrozeatin riboside was considerably less effective. Corolla senescence was preceded by a rise in cytokinin O- glucoside level, O-glucosyldihydrozeatin being the principal glucoside formed. Exogenous ethylene promoted conversion of dihydrozeatin to O- glucosides, but not 7-glucoside, and of zeatin riboside to adenosine and AMP. Hence it appears that ethylene production which induces corolla senescence also promotes inactivation of cytokinins by O-glucosylation and degradation and this may facilitate the senescence process. The use of cellulose TLC to separate cytokinins is discussed.