On the Uptake, Metabolism and Retention of [3H] Gibberellin A1 by Barley Aleurone Layers at Low Temperatures

Barley (c.v. Himalaya) aleurone layers were incubated in [(3)H]gibberellin A(1) (GA(1)) at low temperatures. At 3 and 4 C, (3)H-activity was steadily accumulated in aleurone layers, and this accumulation was correlated with significant [(3)H]GA(1) metabolism. At 1 and 1.5 C, metabolism could not be detected, and at these temperatures aleurone layers equilibrated with the [(3)H]GA(1) concentration in the incubation medium. At equilibrium, the total amount of (3)H-activity per unit volume in the aleurone layers was higher than in the incubation medium. Aleurone layers incubated at 0.5 C for 72 hours with [(3)H]GA(1) in the presence of saturating levels of carrier GA(1) consistently retained lower levels of (3)H-activity than when incubated in [(3)H]GA(1) alone. The retention of [(3)H]GA(1) was unaffected by saturating levels of carrier GA(8). GA(1) retained by barley aleurone layers that were incubated at 0.5 C for 72 hours was able to induce alpha-amylase synthesis when aleurone layers were subsequently washed and transferred to a gibberellin-free medium at 25 C.