Catalyzes the oxidation of cytokinins, a family of N(6)-substituted adenine derivatives that are plant hormones, where the substituent is an isopentenyl group. A + H2O + N(6)-dimethylallyladenine = 3-methyl-2-butenal + adenine + AH2 Expressed in the vascular system of roots, of young growing leaves and of the most apical portion of the growing stem. No expression in the root apical meristem. In flowers, restricted to the vascular bundles and transmitting tissue of developing gynoeciae. Expressed during the maturation phase of stomatal guard cells but not in fully mature stomata. In the root vasculature, detected soon after germination, with a maxima around the lateral root primordia. Belongs to the oxygen-dependent FAD-linked oxidoreductase family. Truncated N-terminus.