
%0 Journal Article
%A Letham, David S. 
%A Smith, Noel G. 
%A Willcocks, David A. 
%T Cytokinin metabolism in <emph type="2">Narcissus</emph> bulbs: chilling promotes acetylation of zeatin riboside
%J Functional Plant Biology
%D 2003/06/06
%V 30
%N 5
%P 525-532
%K chilling, cytokinin metabolism, daffodil, Narcissus, O-acetylzeatin riboside.
%R https://doi.org/10.1071/FP02097
%U https://www.publish.csiro.au/paper/FP02097 
%X The levels of the cytokinins zeatin, dihydrozeatin and N6-(isopent-2-enyl)adenine and the corresponding 9-ribosides were determined in whole Narcissus pseudonarcissus L. bulbs after onset of summer dormancy, and after storage of the dormant bulbs at 4 or 15&#176;C under moist conditions. The cytokinin level was increased at both temperatures; the dominant cytokinin at 15&#176;C was zeatin riboside but at 4&#176;C the free base, zeatin, was the principal cytokinin. The metabolism of 3H-labelled zeatin, zeatin riboside and 6-benzylaminopurine was studied in scales and base plates excised from bulbs previously held at 4 or 15&#176;C. The chilling treatment promoted conversion of [3H]zeatin riboside to O-acetylzeatin riboside (an unusual cytokinin metabolite) in the excised base plate and inhibited 9-riboside formation from 6-benzylaminopurine. Chilling also promoted formation of O-acetylzeatin riboside from [3H]zeatin in excised scale tissue. Endogenous O-acetylzeatin and O-acetylzeatin riboside were concentrated in the base plate. Relative to zeatin riboside, O-acetylzeatin riboside was degraded to adenosine and related compounds less rapidly in the leaf cluster. Since acetylation of the zeatin side chain enhances activity in cytokinin bioassays, O-acetylzeatin riboside may play a role in leaf development following chilling of Narcissus bulbs. 
