Effect of GA3 spraying on lignin and auxin contents and the correlated enzyme activities in bayberry (Myrica rubra Bieb.) during flower-bud induction

The effect of gibberellic acid (GA(3)) spraying on the contents of lignin and auxin, and the activities of correlated enzymes during flower-bud induction was determined in 13-year-old bayberry trees (Myrica rubra Bieb.) in the year of low crop. The results show that the activity of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) in the leaves of the control trees reached the maximum in turns during the period of flower-bud induction, catalyzing the biosynthesis of lignin which was depleted during flower-bud initiation. GA(3) spraying during flower-bud induction significantly inhibited the activities of PAL, PPO, POD and IAA-oxidase (IAAo), and increased the level of indole-3-acetic acid (IAA), delaying the biosynthesis of lignin in leaves of the current shoots, as well as inducing the more vigorous growth and inhibiting flower-bud initiation and formation. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.