Recent advances in studies on the dwarfing mechanism of apple rootstocks

Measurements were made of concentrations and rates of translocation of auxins in shoots of the apple rootstocks M.27, M.9, MM.106 and MM.111. No differences were recorded in the concentrations of auxins present in shoots. However, with invigorating rootstocks, more auxin was translocated through the rootstock shoot, and from scion leaves to rootstock roots, than with dwarfing rootstocks. Sap derived from invigorating rootstocks also had a higher cytokinin content than that from dwarfing rootstocks, whilst the bark of dwarfing rootstocks had higher concentrations of abscisic acid.