ETHYLENE AND FLOWER PETAL SENESCENCE - INTERRELATIONSHIP WITH MEMBRANE LIPID CATABOLISM

Accumulated experimental evidence suggests that the decline in the con tent of membrane components such as phospholipids (PL, is a. key event in flower senescence. This loss of membrane integrity can be modulate d by ethylene, Tile aim of this work was to examine the interrelations hip between ethylene and one of the products of PL metabolism, diacylg lycerol (DAG), during petunia (Petunia hyhrida) flower senescence. DAG 's role was studied using phorbol 12-myristate 13-acetate (PMA), which acts similarly in kinase activation. Our results demonstrate for the first time a senescence-relate transient increase in the content of DA G in petunia plasma membranes, The climacteric-like ethylene rise asso ciated with petal wilting appeared in petunia flowers well after PL de gradation and DAC increase had commenced. The appearance and peak magn itude of the ethylene rise was enhanced or increased, respectively, by PMA treatment. thereby accelerating appearance and magnitude of all s enescence parameters assayed. Conversely, suppression of ethylene acti on by silver thiosulfate (STS) resulted in retardation of flower wilti ng as well as in abolishment of the PMA-enhancing effects on senescenc e. The results suggest an active role for lipid metabolites like DAG i n enhancing flower senescence, through regulation of ethylene producti on and action, or possible activation of kinases. This sequence of eve nts implies that ethylene is a mediator of flower senescence, rather t han a trigger of the process.