The first natural cytokinin was discovered by Letham et. al,. 1963 as Zeatin. About 18 cytokinins have also been discovered e.g., dihydrozeatin, IPA, benzyl adenine. Roots seem to be the major source of cytokinin synthesis. From roots the cytokinins pass upwardly through xylem. Some cytokinin synthesis also takes place in other areas where cell divsions are occurring like endosperm region of seeds, growing embryo and developing seeds. Coconut milk is rich source of cytokinin.