As it was expected, when 0.5 mmol L−1CA solution was appliedat 30 DAFB, the russet formation of ‘Golden Delicious’ apple was sig-nificantly inhibited since the young fruit stage (Fig. 2). In fact, wetried CA concentrations including 0.05, 0.5 and 5 mmol L−1in 2012,and found that all concentrations had significant inhibition while0.5 mmol L−1was the most effective. In 2013, we tried more narrowconcentrations from 0.14 to 0.71 mmol L−1, and the results turnedout that 0.56 mmol L−1was the most effective (data not showed).Thus, we believe that CA concentration at about 0.5 mmol L−1isthe best in inhibiting fruit russeting of ‘Golden Delicious’ apples.In this study, we presented evidence that exogenous CA treatmentincreased the levels of CA and total flavonoids (Fig. 3), but inhibited lignin accumulation in apple peels (Fig. 4). This suggests that theCA treatment resulted in an up-regulation of the whole metabolismof phenylpropanoids, but a down-regulation of lignin biosynthe-sis. Since the russet formation is originated from secondary corkcambium activation and suberification of epidermical cell walls (Knoche and Grimm, 2008), lignin biosynthesis is considered to beessential in the process of russet formation. When CA was applied to the fruit surface, lignin accumulation as well as russet formation was prevented (Fig. 2).