The Influence of Gibberellic Acid and Temperature on the Growth Rate of Avena sativa Stem Segments

A micro-growth measuring technique was used to determine the growth response of stem segments of Avena sativa cv. Avon to a variety of gibberellic acid (GA₃) concentrations over a range of incubation temperatures. Growth rate varied with GA₃ concentration, the temperature at which the rate was measured, and the growth temperature of the plants prior to excision of the segments. The curves relating segment extension rates to temperature were affected by GA₃ such that the linear portion of the curve was shifted to higher rates as GA₃ concentration was increased. The results seem to be analogous to the GA₃-induced shifts of thermally induced phase transitions in glucose leakage from liposomes, observed earlier (Wood, Paleg 1974 Aust J Plant Physiol 1: 31-40).