PHENOLS AND THE DWARFING MECHANISM IN APPLE ROOTSTOCKS
A proposed dwarfing mechanism for apples is described in which the bark of the rootstock plays a key role in the system. The growth inhibiting properties of the bark may be associated with the phenols present in the bark. Lettuce hypocotyl bioassay responses are presented that show the level of many phenols in the bark is more than adequate to induce growth inhibition. Benzoic acid, which was found only in the roots, also proved to be a potent growth inhibitor.
Lockard, R.G. and Schneider, G.W. (1981). PHENOLS AND THE DWARFING MECHANISM IN APPLE ROOTSTOCKS. Acta Hortic. 120, 107-112