The biosynthesis of cytokinins: A report submitted in partial fulfilment of the requirements for the Degree of B.Sc. Honours in the University of Canterbury

Abstract

The purpose of the present project was to investigate further the biosynthesis of cytokinin by following the incorporation of 2-C¹⁴ mevalonate into the hormone and the substituted adenines of tRNA produced by potato callus. (1) Growth of the Callus and the Labelling Experiments: Incorporation of 2-¹⁴C-mevalonate into the cytokinin and tRNA. (2) Extraction of Free Cytokinin and tRNA : Free cytokinin were extracted from aqueous medium while the tRNA was extracted from the callus itself, purified and then hydrolysed with an enzyme mixture which would release the free nucleosides. (3) Purification: Purification by TLC in two solvent systems, watersaturated butanol and chloroform:methanol (9:1). (4) Radioactive Count: The incorporation of ¹⁴C was measured by scintillation counting. Specific activity was used to compensate for some loss in the amount of cytokinin during the experiment and the presence of pools of free cytokinin and tRNA of different sizes.