Strong evidence for a role of auxin in apical dominance is provided by the
classic Thimann-Skoog experiment (Proceedings of the National Academy of Sc
iences, USA 19: 714-716, 1933) wherein exogenous auxin applied to a decapit
ated shoot represses outgrowth of the next lower lateral bud. Although apic
al dominance in most herbaceous species can be restored by this auxin treat
ment, such is not the case with wild-type Arabidopsis thaliana. In the pres
ent study, it has been demonstrated that apical dominance can be partially
or fully restored with exogenous auxin (1 % naphthaleneacetic acid, NAA) ap
plied to the decapitated shoot of the axr3-1 mutant which is thought to be
hypersensitive to auxin. A similar repressive response to auxin (1 muM NAA)
was also shown in an in vitro assay with detached nodes. The role of AXR3
as a gene mediating auxin response is thus supported. (C) 2000 Annals of Bo
tany Company.