Role of ethylene and abscisic acid in physicochemical modifications duringmelon ripening

Hormonal metabolism associated with fruit ripening in two cantaloupe muskme lon cultivars, Talma and Manta, has been studied. The ethylene crisis began on day 33 after fruit set, reaching the maximum values of internal ethylen e concentration and ethylene production rate on day 35 after fruit set. Thi s was the optimum moment for consumption as shown by the higher content in soluble solids, ripening index, sensory analysis, and color parameter value s. The b parameter and the bla quotient values in peel were good indicators of the maturity stage, the optimum moment for harvesting being about day 3 3 after fruit set (when autocatalytic ethylene synthesis has begun), with v alues of 20 and 5 for the b parameter and bla quotient, respectively. In bo th cultivars, free 1-aminocyclopropane-1-carboxylic acid (ACC) content incr eased until day 35 after fruit set and conjugated ACC increased in postclim acterium. The increase in both ACC-synthase and ACC-oxidase activities toge ther could be responsible for the climacteric ethylene production. Signific ant differences in the abscisic acid evolution in Talma and Manta cultivars were reached, and also a possible stimulation of ethylene by this hormone could be established.