Mechanism of the Increase of Polyphenol Oxidase Activity in Pineapple Fruit Induced by GA3

No increase in polyphenol oxidase (PPO) activity was found by addition of GA3 solution in the enzyme extraction. But acid phosphatase activity was found to be increased in pineapple fruit (Armnas comosus (L.) Merr. ) treated with GA3, which was mainly caused by the significant increase in inorganic phosphate (Pi) content. Phospholipase D activities decreased gradually during the period of fruit ripening but GA3 treatment slowed down these processes. On the other hand, the increase of PPO activities in fruit treated with GA3 was enhanced by the addition of ABA treatment.