Kiwifruit ripening was markedly affected by SNP and O3. Following harvest, kiwifruit (cv. ‘Hayward’) were treated with SNP (100 μm for 10 min) or water (control) and then cold stored (0 °C) in the absence or in the presence of O3 (0·3 μL L–1) for 2 or 6 months. All experimental fruit were then allowed to ripen at room temperature (20 °C). The arrow indicates over-ripening symptoms (visual discoloration). (A) Effects of SNP and O3 on the kiwifruit phenotype following 2 or 6 months cold storage plus 14 or 8 d ripening at 20 °C, respectively. (B, C) Changes of fruit firmness of the outer pericarp (B) and columella (C) in kiwifruit during ripening at 20 °C for 14 or 8 d following 2 or 6 months cold storage, respectively. Each value represents the mean of three biological replications of ten fruits analysed at each ripening stage. The least significant difference (LSD, P = 0·05) is given in each individual figure.