| Abstract: | Exogenously applied 8-14C-kinetin is rapidly taken up by seeds of lettuce (Lactuca sativa L. cv. Grand Rapids). Radioactive metabolites were extracted and purified by solvent fractionation, column and paper chromatography. The primary metabolite was identified as the 9-riboside-5′-monophosphate. As germination proceeds, some kinetin is released from this bound storage form, giving a maximum level of free kinetin at 12 hours after imbibition. After this time the concentration of ribotide increases while the concentration of free base decreases. Other metabolites are the 9-riboside, AMP and IMP. It is suggested that a required amount of free base cytokinin is necessary by 12 hours after imbibition. This concentration of free cytokinin may act as a physiological trigger for later events during germination. |
