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 Very weak expression in the young shoot tissues around two weeks after germination (PubMed:14555694). Present in the center of the floral meristem and the boundary between long stamen primordia and gynoecial primordia (PubMed:26390296). Regulated by GATA18/HAN. Belongs to the oxygen-dependent FAD-linked oxidoreductase family.