Relation between the Formation of Parthenocarpic Berries and Endogenous Plant Hormone Contents in Seedless Grape Cultivars.

The contents of the endogenous plant hormones, gibberellin (GA) , indoleacetic acid (IAA) and abscisic acid (ABA) , were compared between 'Himrod Seedless' and the seeded 'Campbell Early' berries to clarify the mechanism of seedlessness in grapes.1.Although no difference was found in the kinds of GA-like substances in the berries of both cultivars from 3 days before anthesis to anthesis, the 'Himrod Seedless' berries had higher contents of GA-like substances than did those of 'Campbell Early'.2. The IAA-contents of 'Himrod Seedless' berries increased 3 days before anthesis and peaked 3 days after anthesis ; whereas, in 'Campbell Early' berries the increase began 3 days after anthesis and peaked on the 14th day.The time of the maximum IAA-content peak differed between these cultivars.3. The changing patterns for the ABA contents of the berries of both cultivars were very similar.The ABA content of 'Himrod Seedless' berries, however, was always somewhat higher than was that of 'Campbell Early'.4. The contents of GA-like substances and ABA in degenerated ovules (seeds) of 'Himrod Seedless' 21 days after anthesis were lower than were those in normal seeds of 'Campbell Early' .