Abstract: Changes of endogenous abscisic acid(ABA) and gibbcrellic acid(GA3) in shoots of open fields and plastic film enveloped young apple tree of Malus pumila on stock of Mains micfomalus during the overwintering period were determined by GC and HPLC respectively.The results showed that the contents of ABA in shoot bark of open fields and plastic film enveloped trees were high in the earlier stage of winter, reached their peaks (1.15 × 10-3 and 1.28 × 10-3mg ? g-1) on Jan.30 and decreased quickly after Feb.20.In the later stage of winter the ABA content of plastic film enveloped tree was lower than that of open fields tree.The content of ABA in lateral vegetative buds of plastic film enveloped tree reached its peak (1.47 × 10-3 mg ? g-1) on Jan.20, then decreased raspidly within 15 days and remained very low (about 7.8 × 10-5 mg ? g-1) from Mar.5 to Apr.5.The content of GA3 in vegetative buds increased during the overwintering period.GA3 content of plastic film enveloped tree increased quicker than that of open fields tree and reached its peaks (8.73 × 10-5 and 1.15× 10-4 mg ? g-1) on Feb.5 and Mar.20.The GA3 content of plastic film enveloped tree was higher than that of open fields tree on Apr.5.It is concluded that GA3 and ABA in the shoots play an important regulatory role during the overwintering period.

Key words: Shoot of apple, Envelopment with plastic film, ABA, G A3