The relationship between elongation growth and the incorporation of 3Hgibberellin A1(3HGA1) into a 2,000gpelletable (2KP) fraction from lettuce (Lactuca sativaL., cv. Arctic) hypocotyl sections has been examined. Sections were loaded with incremental amounts of GA1under 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 GA1uptake 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
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