Abstract: The regulating effects of IAA, GA and ABA on activities of SDH and SOX were studied in the fruits of‘Starkrimson’ apple through disk incubation technique. The results showed that the activities of SOX had significant negative correlation with the concentrations of IAA, GA and ABA during fruit developmental period. However, the activities of SDH only had significant negative correlation with GA contents. The results also indicated that exogenous IAA and GA highly increased the activities of SOX in apple fruit, especially to the fruit at early developmental period. Moreover, the exogenous ABA showed the highest regulating effects on SOX activity in the fruit at late developmental stage. On the other hand, exogenousABA increased the SDH activity significantly, however, IAA only increased the activities of SDH.

Key words: Apple, Hormone, Sorbitol, Sorbitol dehydrogenase, Sorbitol oxidase