THE ROLE OF ETHYLENE IN COROLLA UNFOLDING IN IPOMOEA NIL (CONVOLVULACEAE)

The roles of ethylene in corolla growth and senescence have been extensively studied; light, temperature, and abscisic acid (ABA) have already been implicated in rapid corolla opening (unfolding) in morning glory. In the present study, a possible interaction between ABA and ethylene production was examined. While applied ABA promoted corolla unfolding, it also promoted ethylene production. Furthermore, the effect of ABA could be eliminated by the ethylene biosynthesis inhibitors, aminoethoxyvinyl glycine (AVG) and cobalt ions. Simultaneously applied aminocyclopropane carboxylic acid (ACC) augmented the ABA response, but ACC applied alone promoted corolla unfolding as effectively as ABA alone. Measurements of ethylene production during eight successive stages of flower opening showed that the ethylene burst widely reported to occur in opened flowers prior to corolla senescence actually begins before the corolla unfolds. Ethylene production seems to be a later part of the sequence of biochemical events that leads to both corolla unfolding and synchronized inrolling and senescence.