A brief history of cytokinin research
1913: Gottlieb Haberlandt discovers that a compound found in phloem can stimulate cell division in potato parenchyma.
1941: Johannes van Overbeek discovered that the milky endosperm from coconut also had this ability.
1955: Carlos Miller, a graduate student in Folke Skoog's laboratory at the University of Wisconsin, identifies kinetin from herring sperm.
1956: Miller and Skoog demonstrate that the ration of auxin:cytokinin alters organogenesis in vitro (see below)
1961-1963: Miller and Letham independently isolate zeatin, a naturally occurring cytokinin, from maize.
1998-present: Components of signaling pathway are identified.
See also Dr. Rick Amasino's excellent article describing the discovery of kinetin.
Figure 1: Role of cytokinin and auxin in regeneration of callus cells. Note that at high cytokinin levels, shoots are formed and at relatively high auxin levels roots are formed. From: Skoog and Miller (1965) "Molecular and cellular aspects of development".