Locular Gel Formation in Developing Tomato Fruit and the Initiation of Ethylene Production

Abstract

Abstract Ethylene production by developing tomato fruit (Lycopersicon esculentum Mill., cv. Sunny) increased 3- to 5-fold at the time of gel formation in the locules, followed by a larger (20-fold) increase at the breaker stage. When the levels of ACC and the activities of ACC synthase and ethylene-forming enzyme (EFE) were measured in different portions of the fruit during maturation, the first increases were observed in the locular tissue coincident with gel formation, followed by changes in the placental and columella tissue. Later changes in ACC, ACC synthase, and EFE in the radial and outer pericarp corresponded to the marked increased in ethylene production that occurred at the breaker stage. Treatment of immature fruit with 50 μl·liter−1 ethylene enhanced the rate of gel formation markedly with no apparent lag time, but the stimulation was dependent on continuous presence of ethylene. These results indicate that the onset of ethylene production occurs in the locule tissue of green tomato fruit prior to its initiation in the pericarp and that the locule cells may develop greater sensitivity to ethylene at an earlier stage than pericarp cells. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).