ROLES OF ETHYLENE PRODUCTION AND SENSITIVITY IN SENESCENCE OF CARNATION FLOWER (DIANTHUS-CARYOPHYLLUS) CULTIVARS WHITE SIM, CHINERA AND EPOMEO

Longevity of carnation (Dianthus caryophyllus) cultivar Chinera was much longer than that of cultivar White Sim. In <Chinera>, the increases in 1-aminocyclopropane-1-carboxylic acid synthase (EC 4.4.1.14) activity, ethylene-forming enzyme activity, ethylene production and membrane permeability, associated with the start of the senescence process, occurred later, and the maximum levels during senescence were much lower than in <White Sim>. Ethylene treatment stimulated the activity of the ethylene biosynthetic pathway and associated enzymes but stimulation was less in <Chinera> than in <White Sim>. Ethylene dose-response experiments showed lower sensitivity in <Chinera> while binding site characteristics were supposedly similar in the two cultivars. The reduced sensitivity of Chinera> to ethylene, therefore, is apparently determined at a point beyond the receptor, presumably in the signal transduction chain. In cultivar Epomeo, which is the progeny of <Chinera> and a non-commercial breeding line <<9775>>, ethylene production and sensitivity showed the same trends as in <Chinera>, showing that the decreased sensitivity and the associated longer vase life is an inheritable feature.