Is ABA the earliest upstream inhibitor of apical dominance?

Abstract

Axillary bud growth - and specifically its release from apical dominance - has been a longstanding and complex area of research. Many phytohormone systems, as well as sugar signaling, have been implicated. Now, Holalu and Finlayson (see pages 943-952) have found compelling evidence that a much less-studied hormone in this context - abscisic acid (ABA) - may, in fact, be one of the first upstream factors regulating apical dominance responses to the R:FR ratio.