INTERACTION OF INDOLYL ACETIC ACID AND GIBBERELLIC ACID IN THE SYNTHESIS OF α‐AMYLASE BY BARLEY ALEURONE

S ummary When slices of barley endosperm were supplied with a mixture of 10 −4 M gibberellic acid and indolyl acetic acid (10 −4 or 10 −10 m) continuously for 36 hours the amount of α‐amylase formed was significantly less than that formed in response to gibberellic acid alone. However, pre‐treatment of slices with a mixture of 10 −10 M indolyl acetic acid + gibberellic acid for 8 hours followed by incubation in gibberellic acid alone resulted in enhanced levels of production of α‐amylase. Removal of coleoptile tips from germinating grains was followed by diminished synthesis of α‐amylase in the endosperm, but the level of α‐amylase formed could be restored to that found in the intact grain by supplying 10 −7 M indolyl acetic acid to the coleoptile stump. It is suggested that indolyl acetic acid, migrating from the coleoptile tip, is involved not only in the process of lignification in the scutellum but also in the preliminary stages of gibberellin‐mediated α‐amylase formation in the aleurone.