• The cytokinins are a class of organic molecules that regulate growth and development through cell division in plants.
  • In the early 1900s, researchers noticed that some plant extracts, especially coconut milk, had the ability to stimulate cell division, but the identity of the active agent was unknown.
  • Enter Folke Skoog (of Murishage and Skoog medium fame) who, working in the 40s and 50s, identified the first cytokinin, kinetin.
  • Kinetin does not occur in plants but was discovered after trying many substances in an effort to produce the same effect as coconut milk.
  • A well-known plant-produced cytokinin is zeatin, found in coconut milk, but first isolated from corn kernels (hence the name, since corn is Zea mays).
  • The name “cytokinin” is indicative of its action. Cytokinins promote “cytokinesis,” more commonly known as cell division.
  • Of the more than 200 known cytokinins (both natural and synthetic), most are structurally derived from adenine, which also provides the ‘A’ in the ATCG sequences of DNA.
  • The effects of cytokinins are diverse and include activity with respect to bud and leaf initiation and expansion, apical dominance, chlorophyll biosynthesis, and many others.
  • Although, depending on the stage of growth and development, cytokinins can be found in abundance in just about any plant tissue, the highest concentrations are found in root tips, embryos, and apical buds.
  • Cytokinins are important in plant tissue culture and are available commercially in purified form from many suppliers.