title: The role of endogenous gibberellins in the formation of α-amylase by aleurone layers of germinating barley caryopses.
abstract: Using sensitive and selective immunological assays we have shown that in germinating caryopses of Hordeum vulgare L. cv. Himalaya, the level of gibberellin A4 (GA4) rises approximately 18-to 20-fold shortly (2-4 h) before α-amylase activity increases. Gibberellin A4 is the predominant immunoreactive gibberelin during these developmental stages and reaches a peak amount of approximately 9 pmol per caryopsis about 48 h after imbibition. Isolated aleurone layers produce GA4 in the presence of an exogenous gibberellin, such as GA1, which is not a biosynthetic precursor for GA4. Experiments with inhibitors of gibberellin biosynthesis indicate that gibberellin synthesis is required in this tissue for the induction of α-amylase. The inductive effect of exogenously applied GA1 is indirect and appears to be mediated by GA4. Embryos form predominantly GA1; however, very little of this material is released by isolated embryos into the incubation medium. The results presented make it unlikely that the role of the embryo in the process of α-amylase induction in aleurone layers is to provide gibberellins or gibberellin precursors.
authors.affiliation: Lehrstuhl für Pflanzenphysiologie, Ruhr-Universität, Postfach 102148, D-4630, Bochum, Federal Republic of Germany.
authors.forename: R
authors.initials: R
authors.lastname: Atzorn
authors.forename: E W
authors.initials: EW
authors.lastname: Weiler