Submitted to: Proceedings of Plant Growth Regulation Society of America
Publication Type: Proceedings
Publication Acceptance Date: 9/10/2009
Publication Date: 4/29/2010
Citation: Tworkoski, T., Fazio, G. 2010. Hormonal and anatomical effects of apple rootstocks. Proceedings of the 36th annual meeting of the Plant Growth Regulation Society of America, (PGRSA, LaGrange, GA). August 2-6, 2009, Asheville, North Carolina, p. 161. Interpretive Summary:
Technical Abstract: In greenhouse experiments, two-year-old 'Fuji' apple scions (Malus ×domestica, 'Fuji') on size-controlling rootstocks (dwarfing to vigorous), were grown for one season and shoot growth was measured to confirm size-controlling effects. In the next season, xylem sap was collected to determine hydraulic conductance and root-produced concentrations of abscisic acid (ABA). Less hydraulic conductance and higher ABA flux was associated with the more dwarfing rootstocks. Anatomies of scion and rootstock stem cross-sections were analyzed and vessel diameter was found to be reduced in scion on the more dwarfing rootstocks. The changes in xylem anatomy, hydraulic conductance, and ABA concentrations may be factors associated with size-controlling processes of apple rootstocks. Higher ABA concentrations may have changed xylem development and reduced hydraulic conductance in size-controlling processes of apple rootstocks. Experiments are needed to establish temporal relationships between xylem vessel development and root-produced signals such as ABA to clarify their role in regulating apple tree size. Improved knowledge of such growth regulating mechanisms can assist in developing new rootstocks that are needed for small, efficient apple trees in high density plantings.