“…Although many changes occur during this period, which may coincide temporally with ABA accumulation, the possibility of a direct relationship between ABA and ACC accumulation is supported further by the fact that ABA treatment has been reported to enhance ethylene production in different plant tissues of several species (Brady, 1987;Gómez Cadenas et al, 1996;Riov et al, 1990;Tari and Nagy, 1996;Vendrell and Buesa, 1989). In contrast, no similar relationship was found for the peel tissue, possibly indicating differentially regulated ethylene biosynthesis in peel and pulp tissues, as previously suggested for 'Granny Smith' apples (Lara and Vendrell, 1998b) and 'Passe-Crassane' pears (Pyrus communis L.) (Lara and Vendrell, 1998a). Ethylene and carbon dioxide production, fruit firmness, and pigmentation have been used as markers to identify maturity stages of climacteric fruit, but the physiological changes occurring during apple fruit development differ among cultivars (Kondo et al, 1991;Mansour et al, 1986;Gemma, 1990 and.…”