Apical dominance in Pssu-ipt-transformed tobacco

In Pssu-ipt-transformed tobacco, apical dominance was released by defoliati on of the upper nodes, while the apex remained intact. After defoliation, t he concentration of cytokinins (CKs) increased whereas IAA remained constan t, evoking an increase in the CK/IAA ratio in the buds. Moreover, defoliati on resulted in a tremendous increase in the concentrations of aromatic amin es (AAs): tyramine (TYR), phenethylamine (PEA) and an as yet unidentified c ompound. Although the total aliphatic monoamine and polyamine (PA) concentr ation remained constant, putrescine (PUT) and spermidine (SPD) concentratio ns in the axillary buds decreased, whereas the concentration of spermine (S PM) increased. Similar changes in PAs and AAs could be observed in the buds of untransformed SR1 plants after decapitation, whereas defoliation withou t removal of the apex had no effect. This is the first report on the possib le involvement of PAs and AAs in apical dominance. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.