The synthesis, transport and metabolism of endogenous cytokinins

Present evidence indicates that only the root systems of plants have been shown conclusively to synthesize cytokinins. Although most of these compounds are apparently exported to the shoot via the xylem, there are indications that more attention should be given to the possibility of translocation through the phloem. Within mature leaves the cytokinins derived from the roots are converted to inactive or storage forms by means of glucosylation. While it would appear that glucosylation could occur in all living plant cells whenever the cytokinins are no longer required for active growth, and could provide the plant with a potential reservoir of cytokinins, very little is known with regard to the transport and reutilisation of these compounds.