Uptake and metabolism of radioactive gibberellins by barley aleurone layers

When aleurone layers were treated with labeled gibberellin A1 ((3)H-GA1), gibberellin A5 ((3)H-GA5) and the methyl ester of (3)H-GA5 ((3)H-GA5-ME), radioactivity was accumulated by the tissue for a period of 20-30 h. After this time, radioactivity was released into the medium. Concomitantly, ribonuclease was also liberated by the tissue. The radioactivity accumulated by aleurone layers was associated with polar metabolites of the respective GAs, and the extent of extent of accumulation was a function of the degree of GA metabolism (GA5-ME>GA5>GA1). Accumulation of radioactivity was inhibited in the cold and by the metabolic poisons NaF and dinitrophenol. This was thought to be due to inbition of GA metabolism. The accumulation of (3)H-GA1 in aleurone tissue did not reach saturation when unlabeled GA3 up to 10(-2) M was added to the incubation medium.