NAA restores apical dominance in the axr3-1 mutant of Arabidopsis thaliana

Strong evidence for a role of auxin in apical dominance is provided by the classic Thimann-Skoog experiment (Proceedings of the National Academy of Sciences, USA 19: 714-716, 1933) wherein exogenous auxin applied to a decapitated shoot represses outgrowth of the next lower lateral bud. Although apical dominance in most herbaceous species can be restored by this auxin treatment, such is not the case with wild-type Arabidopsis thaliana. In the present study, it has been demonstrated that apical dominance can be partially or fully restored with exogenous auxin (1 % naphthaleneacetic acid, NAA) applied 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 Botany Company.