Regulators of Cell Division in Plant Tissues1: XIX. THE METABOLISM OF 6-BENZYLAMINOPURINE IN RADISH COTYLEDONS AND SEEDLINGS

Excised immature radish cotyledons were allowed to take up [³H]6-benzylaminopurinefor up to 5 h and were then transferred to cytokinin.free mediumfor various intervals, after which they were extracted. Thecytokinin was rapidly metabolized by the tissue to two mainproducts which accounted for 20 per cent of the extracted radioactivityafter 1 h of uptake, and for 95 per cent after transfer to thecytokinin-free medium. These metabolites were coincident withcytokinin activity on chromatograms of the cotyledon extractand were also formed when 6-benzylaminopurine was supplied to9-d-old derooted seedlings through the transpiration stream.The metabolites were identified by mass spectrometry, u.v. spectroscopy and chemical degradation as 6-benzylarnino-7-glucosylpurineand 6-benzylamino-9. glucosylpurine. Several minor metaboliteswere detected in the derooted seedlings; one was 6-benzylaminopurineriboside while another appeared to possess high cytokinin activity.