Kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson cv. Bruno) was used to investigate the effects of acetylsalicylic acid (ASA, 1.0 mmol/L, pH 3.5) and ethylene (100 mL/L) treatments on changes at endogenous salicylic acid (SA) levels and other senescence-related factors during fruit ripening and softening at 20 ℃. The level of endogenous SA in ripening fruits declined and a close relationship was observed between the change at endogenous SA level and the rate of fruit ripening and softening. ASA treatment elevated SA level in the fruit, slowed down the increases in lipoxygenase (LOX) and allene oxide synthase (AOS) activities, decreased the O22-. production in the preclimacteric phase and the early phase of ethylene climacteric rise, maintained the stability of cell membrane, inhibited ethylene biosynthesis, postponed the onset of the ethylene climacteric, and delayed the process of fruit ripening and softening. On the contrary, application of ethylene to ripening kiwifruit resulted at a lower SA level, an accelerated increases in the activities of LOX and AOS and the rate of O22-. production, an elevated relative electric conductivity and an advanced onset of ethylene climacteric, and a quicker fruit ripening and softening. It is suggested that the effects of ASA on ripening kiwifruit can be attributed to its ability to scavenge O22-. and/or to maintain stability of cell membrane.
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