Cytokinins (CKs) are plant hormones promoting cell division and differentiation,
morphogenesis in tissue culture, leaf expansion, bud formation, delay of leaf senescence and
chloroplast development (reviewed in Rijavec & Dermastia, 2010). Natural CKs are adenine
derivatives and based on the side chain moiety, they can be divided into two subgroups:
isoprenoid and aromatic cytokinins.