The bioassay of gibberellins.

A bioassay is described which is dependent upon the fact that gibberellin induced α-amylase release from barley half-seeds is proportional to the logarithm of gibberellin concentration applied. This bioassay has been successfully applied to the estimation of gibberellin-like substances in plant extracts. The bioassay has the following advantages: 1) Release of α-amylase is one step closer to the primary site of action of GA; 2) release of α-amylase is not affected by solvent residues and is apparently completely specific for gibberellin; 3) release of α-amylase is not affected by substances other than gibberellins present in crude plant extracts.