Interaction of [3H]gibberellin A1 with a sub-cellular fraction from lettuce (Lactuca sativa L.) hypocotyls |
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Authors: | John L Stoddart Paul D Williams |
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Affiliation: | (1) Welsh Plant Breeding Station, SY23 3EB Aberystwyth, Dyfed, U.K.;(2) Present address: Hatfield Polytechnic, Hatfield, Herts, U.K. |
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Abstract: | The relationship between elongation growth and the incorporation of 3H]gibberellin A1 (3H]GA1) into a 2,000g pelletable (2KP) fraction from lettuce (Lactuca sativa L., cv. Arctic) hypocotyl sections has been examined. Sections were loaded with incremental amounts of GA1 under conditions where growth was arrested (5° C) or permitted (30° C) and, after 16 h, all were transferred to a GA-free
medium at 30° C. Growth and 2KP radioactivity were measured at this point and after a further 24 h in the chase medium. Uptake
was reduced by 80% at 5° C, as compared to 30° C, but 2KP labelling and protein synthesis were only reduced by half. The growth
rate of the 5° C pretreated sections during the chase period was comparable to that observed during the pulse in the 30° C
material but the dose/response relationship was flatter. Low temperature sections incorporated a much higher percentage of
GA1 uptake into the 2KP fraction (27% at maximum) but the absolute levels of labelling at this temperature were lower than those
measured at 30° C. The data are interpreted as showing that 2KP labelling is not a consequence of growth. It must either precede
response or be an unconnected concurrent process. |
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Keywords: | Gibberellin Growth temperature Lactuca Temperature (gibberellin) |
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