Regulation of Growth in Avena (Oat) Stem Segments by Gibberellic Acid and Abscisic Acid

The purpose of this study was to analyze the nature of the interaction between gibberellic acid (GA 3 ) and abscisic acid (ABA) in the regulation of growth in excised Avena (oat) stem segments. Growth, compared to sucrose controls, was inhibited by ABA in the range of 10 −4 to 10 −6 M . GA 3 -promoted growth was also inhibited by ABA in the same concentration range. A Lineweaver-Burk analysis of the interaction between GA 3 and ABA indicated that ABA acts in a non-competitive fashion with GA 3 . This same result was obtained previously with GA 3 -indoleacetic acid (IAA) and GA 3 -kinetin interactions with Avena stem sections. Our results indicate that ABA can inhibit GA 3 -promoted growth within physiological concentrations, and that it is probably acting at a different physiological site from that for GA 3 .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74746/1/j.1399-3054.1974.tb03674.x.pd