title: Signals controlling root suckering and adventitious shoot formation in aspen (Populus tremuloides).
abstract: We determined the effects of removal of leaves, stem axillary buds, or the entire shoot on root suckering (adventitious shoot formation by roots) and basal stem sprouts in 3- and 4-year-old potted seedlings of aspen (Populus tremuloides Michx.). The greatest number of root suckers (67.9 +/- 8.5 per plant) emerged after excision of the entire shoot. Defoliated and debudded stems were the major source of inhibitory agents for root suckering, although axillary buds and developing new leaves also exerted a significant inhibitory effect. Removal of mature leaves had only a minor effect on root suckering. Removal of a continuous band of bark (girdling) at the base of the stem consistently stimulated growth of adventitious shoots from the stem below the girdle and occasionally promoted root suckering. Exogenous application of indole-3-acetic acid to excised stumps inhibited root suckering and basal stem sprouting. Naphthylphthalamic acid (NPA), an auxin polar transport inhibitor, had no effect on root suckering or stem sprouting when it was applied to the bark of the basal stem. However, NPA significantly increased root suckering when it was applied to the exposed surface of xylem after girdling. These results suggest that polar transport of auxin in the xylem parenchyma is an important inhibitor of root suckering. On decapitated stems, vacuum extraction of xylem sap from the root system lowered the frequency of root suckering compared with decapitation alone, indicating that substance(s) originating in the root system also play a significant role in controlling root suckering.
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada T6G 2H1. xwan@ualberta.ca
authors.forename: Xianchong
authors.initials: X
authors.lastname: Wan
authors.forename: Simon M
authors.initials: SM
authors.lastname: Landhäusser
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Lieffers
authors.forename: Janusz J
authors.initials: JJ
authors.lastname: Zwiazek
mesh_terms: D007210:Indoleacetic Acids / Q000494:pharmacology; D010797:Phthalimides / Q000494:pharmacology; D018517:Plant Roots / Q000254:growth & development / Q000502:physiology*; D018520:Plant Shoots / Q000254:growth & development / Q000502:physiology*; D032107:Populus / Q000254:growth & development / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D007210:Indoleacetic Acids; D010797:Phthalimides; C002687:alpha-naphthylphthalamic acid; C030737:indoleacetic acid