Regulators of cell division in plant tissues |
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Authors: | R E Summons B Entsch D S Letham B I Gollnow J K MacLeod |
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Institution: | (1) Research School of Biological Sciences, Australian National University, P.O. Box 475, 2601 Canberra City, A.C.T., Australia;(2) Research School of Chemistry, Australian National University, P.O. Box 475, 2601 Canberra City, A.C.T., Australia |
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Abstract: | The cytokinins in certain fractions prepared from extracts of immature sweet-corn (Zea mays L.) kernels using polystyrene ion-exchange resins have been further investigated. Cytokinins active in the radish cotyledon bioassay were purified from these fractions and identified as 9- -D-glucopyranosylzeatin, 9- -D-glucopyranosyldihydrozeatin, O- -D-glucopyranosylzeatin. and O- -D-glucopyranosyl-9- -D-ribofuranosylzeatin. In addition, compounds which resemble zeatin and its glycosides in chromatographic behaviour and in ultraviolet absorption characteristics were purified from extracts of the same material by high-performance liquid chromatography. In addition to zeatin and zeatin riboside, the following compounds were identified unambiguously: O- -D-glucopyranosyl-9- -D-ribofuranosyldihydrozeatin, O- -D-glucopyranosyldihydrozeatin, and hihydrozeatin riboside. A further compound was tentatively identified as O- -D-glucopyranosylzeatin, and at least two unidentified compounds appeared to be new derivatives of zeatin. In identifying the above compounds, chemical-ionization mass spectrometry proved to be an invaluable complementary technique, yielding spectra showing intense protonated-molecular-ion peaks and also prominent structure-related fragmentation that was either not evident or very minor in the electron-impact spectra. An assessment of the relative importance of the various possible mechanisms for cytokinin modification and inactivation in mature sweet-corn kernels was made by supplying 3H]zeatin and 3H]zeatin riboside to such kernels after excision. The principal metabolites of zeatin were adenine nucleotides, adenosine and adenine, while little of the metabolite radioactivity was attributable to known O-glucosides. Adenine nucleotides and adenine were the principal metabolites of zeatin riboside, while lesser metabolites were identified as adenosine, dihydrozeatin, and the O-glucosides of dihydrozeatin and dihydrozeatin riboside. Side-chain cleavage, rather than side-chain modification, appears to be the dominant form of cytokinin metabolism in mature sweet-corn kernels.Abbreviations CI-MS
chemical-ionization mass spectrum
- EIMS
electron-impact mass spectrum
- GC-MS
combined gas chromatography-mass spectrometry
- HPLC
high performance liquid chromatography
- M+
molecular ion
- MH+
protonated molecular ion
- TLC
thin-layer chromatography
- TMS
trimethylsilyl
- UV
ultraviolet
XXVII=Letham et al. (1979) |
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Keywords: | Cytokinin metabolites Zea mays |
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