Relationship between Ethylene Evolution and Senescence in Morning-Glory Flower Tissue

An excised tissue system consisting of corolla rib segments was developed to study the relationship between senescence and ethylene production in morning-glory flowers (Ipomoea tricolor). Such segments, isolated 1 or 2 days (day −1 or day −2) before flower opening (day 0) passed through the same developmental phases as did the corresponding tissues of the intact organ. When excised on day −1 and incubated overnight, the rib segments turned from purple to blue and changed from a slightly curled to a flat configuration. On day 0, these segments rolled up during the afternoon and turned purple again, as did the ribs of an intact corolla; the rolling up coincided with an increased rate of ethylene production. Premature rolling up and associated ethylene evolution were induced by ethylene or propylene treatment. When segments were excised on day −2 and incubated overnight, there were no changes in color or shape; during day −1, no spontaneous rolling up and little ethylene evolution occurred. Application of ethylene or propylene to these immature segments elicited rolling up but did not stimulate endogenous ethylene production.