Plant hormone interactions: how complex are they?

Abstract

Models describing plant hormone interactions are often complex and weblike.Here we assess several suggested interactions within one experimentalsystem, elongating pea internodes. Results from this system indicate that at least some suggested interactions between auxin, gibberellins (GAs),brassinosteroids (BRs), abscisic acid (ABA) and ethylene do not occur inthis system or occur in the reverse direction to that suggested. Furthermore, some of the interactions are relatively weak and may be of little physiological relevance. This is especially true if plant hormones are assumed to show a log-linear response curve as many empirical results suggest. Although there is strong evidence to support some interactions between hormones (e.g. auxin stimulating ethylene and bioactive GA levels), at least some of the web-like complexities do not appear to be justified or are overstated. Simpler and more targeted models may be developed by dissecting out key interactions with major physiological effects.