The first idea seemed initially more plausible since the structures of xanthophylls and ABA correspond to a large degree. In vitro occurs conversion only upon exposure to strong light and with an extremely low yield, though. This and supplementing in vitro observations called the first assumption into question again. ABA activity alone is not enough to keep the dormancy of buds up in the long term though. On the contrary rises the ABA level during seed and fruit production.
ABA is an efficient inhibitor of germination and occurs in high concentrations in dormant seeds.
The role ABA has during the abscission of fruits and leaves is largely unknown. Though both cases seem to be governed by similar mechanisms has ABA nearly no effect on the abscission of leaves while it shows a clear effect on fruit abscission. Moreover was a regulating effect of abscisic acid on the water balance observed. As soon as the water supply of cut wheat leaf blades is interrupted and the cell turgor decreases raises the concentration of ABA forty-fold within four hours. Comparable data have been collected for other plant species, too.