PMID: 16657045Feb 1, 1969Paper

Control of logarithmic growth rates of tobacco callus tissue by cytokinins

Plant Physiology
J P HelgesonC D Upper


The growth rates of tobacco callus tissues on media containing 10(-6) to 10 mum 6-(gamma,gamma-dimethylallylamino)purine (2iP) were measured. At concentrations of 10(-4) mum and above growth rates were exponential and dependent on cytokinin concentration. At 2iP concentrations of 10(-4) to 0.33 mum, the exponential rate was maintained for 4 to 5 doublings of fresh and dry weight. After this period a linear phase, resulting in approximately 1 doubling of weight, occurred. The growth of tissues on media containing higher than 0.33 mum 2iP was exponential for only about 15 days. At the end of this time, and well before they achieved half their final weight, they exhibited growth which was less rapid than logarithmic but more rapid than linear. Comparisons with zeatin, 6-benzylaminopurine and kinetin indicated that, although the maximum growth rates obtained with relatively high concentrations (0.1-1 mum) were similar, the naturally occurring cytokinins, 2iP and zeatin, promoted faster rates at lower concentrations (10(-3)-10(-2) mum) than did 6-benzylaminopurine and kinetin.


Jul 1, 1966·Proceedings of the National Academy of Sciences of the United States of America·J P Helgeson, N J Leonard
Aug 16, 1966·Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character·M I Bruce, J A Zwar
Apr 7, 1967·Science·R H HallB McLennan

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Jul 1, 1970·Plant Physiology·C D UpperG T Haberlach
Dec 1, 1973·Plant Physiology·J P Helgeson, G T Haberlach

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