POSTHARVEST PERFORMANCE EVALUATION OF PLUM (PRUNUS-SALICINA LINDEL, CASSELMAN) FRUIT GROWN UNDER 3 OZONE CONCENTRATIONS

We investigated the effects of three seasonal atmospheric ozone (O3) c oncentrations on fruit quality, internal breakdown, weight loss, cutic le structure, and ripening characteristics of plum fruit from 3-year-o ld 'Casselman' trees in the 1991 season. Trees were exposed to 12-hour daily mean O3 concentrations of 0.034 [charcoal-filtered air (CFA)], 0.050 [ambient air (AA)], or 0.094 (ambient plus O3 (AA + O)]mul-liter -1 from bloom to leaf-fall (1 Apr. to 31 Oct. 199 1). Fruit quality an d internal breakdown incidence measured at harvest and after 2,4, and 6 weeks of storage at 0C were not affected by any of the O3 treatments . Following an ethylene (C2H4) preconditioning treatment, the rate of fruit softening, C2H4 production, and CO2 evolution was higher for plu ms harvested from the AA + O than from those grown in CFA. Weight loss of fruit from the AA + 0 exceeded that of fruit from CFA and AA. Anat omical studies of mature plums indicated differences in wax deposition and cuticle thickness between fruit grown in AA + O, AA, and CFA. Dif ferences in gas permeability, therefore, may explain the difference in the ripening pattern of Casselman' plum fruit grown in high atmospher ic O3 partial pressures.