GA3 application increased the PPO activity in pineapples (Zhou
and Tan, 1997) and induced PPO gene expression and IB development
in pineapples in the absence of chilling (Zhou et al., 2003b).
In our study, GA3 application increased both IB and PPO activity.
In Trad-see-thong, GA3 application dramatically increased the
endogenous ABA concentration at 14 d while IB rapidly increased
after 14 d. In addition, the degree of IB with GA3 application was
higher at 21 d in Trad-see-thong than in Pattavia. This suggests that
the increase in the ABA concentration may be a sign of the plant’s
defense response against environmental stress. It has been shown
that both the PINPPO1 and PINPPO2 genes of Smooth cayenne-type
pineapple consist of complex sequence homologues to elements of
the GA response complex (Zhou et al., 2003b). Therefore, it is possible
that the induction of PPO activity in pineapples