Determination by Gas Chromatography-Mass Spectrometry of [N(5)]Adenine Incorporation into Endogenous Cytokinins and the Effect of Tissue Age on Cytokinin Biosynthesis in Datura innoxia Crown Gall Tissue |
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| Authors: | Palni L M Tay S A Macleod J K |
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| Affiliation: | Research School of Biological Sciences, The Australian National University, Canberra, A.C.T. 2601, Australia. |
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| Abstract: | In this study gas chromatographic-mass spectrometric techniques have been used to identify and quantify the metabolic incorporation of [15N5]adenine into zeatin and its metabolites by 3-week-old Datura innoxia Mill, crown gall tissue. In a parallel study the levels of endogenous cytokinins were also determined by the stable isotope dilution technique using deuterium (2H)-labeled internal standards. Incorporation levels of the [15N5]adenine after 8 hours of incubation, expressed as a percentage of the endogenous cytokinins, were as follows: zeatin (1.0%), zeatin riboside (1.5%), and zeatin riboside 5′-phosphate (10.2%). These results are consistent with those observed in complementary experiments using [U-14C]adenine, and support the proposal that the cytokinin biosynthesis occurs primarily at the nucleotide level. The effect of tissue age on cytokinin biosynthesis, determined by [U-14C]adenine incorporation into cytokinins by tissues at varying growth stages, indicated a steady increase with time reaching maximal synthesis at five weeks following subculture after which the level of 14C incorporation into cytokinins declined. |
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