Abstract
Although abscisic acid-β-D-glucopyranosyl ester (ABA-GE) had been known to be a physiologically inactive conjugated ABA, the putative compound causing the allelopathic effect of Citrus junos fruit peel was isolated and the chemical structure of the inhibitor was determined as ABA-GE. In addition, an ABA-GE-cleaving enzyme, apoplastic β-D-glucosidase, which releases free ABA from the ABA-GE conjugate pool in the plant tissues, was recently found. In this research, growth inhibiting activity of C. junos, C. unshiu and C. hassaku fruit peel and ABA-GE concentration in their peel were determined, and a good correspondence between ABA-GE concentrations in C. junos, C. unshiu and C. hassaku fruit peel and the inhibitory activities of their aqueous methanol extracts was found. These results coupled with the effectiveness of ABA-GE on inhibition of growth suggested that ABA-GE may play an important role in the allelopathic activity of C. junos, C. unshiu and C. hassaku fruit peel.
