What turns on and off the cytokinin metabolisms and beyond

When compared to animal and insect organisms, plants have a small number of hormones. This is attributed to the complexity of hormone crosstalks among them. Recent studies obtained from model plants, Arabidopsis and rice, have shown the interaction of variety of signalling molecules with phytohormone metabolism and signalling. We review recent and exciting studies in the field of cytokinin, a major classic of phytohormones, by focusing upon the regulation of metabolisms – biosynthesis and degradation of cytokinins. Endogenous factors as well as environmental cues having an impact on the regulation of cytokinin metabolisms are summarized. Practical applications by altering cytokinin metabolisms in crop species are discussed.