Metabolism of [H]Gibberellin A(20) in Light- and Dark-grown Tobacco Callus Cultures.

The growth of tobacco callus in culture (previously shown to contain gibberellin [GA]-like substances), and its ability to metabolize [(3)H]-GA(20) were examined. Growth rates, in the presence and absence of exogenously applied GA, were examined in light and dark conditions. Dark-grown callus grew at a much faster rate than light-grown and [(3)H]GA(20) was metabolized much more rapidly in darkness than in light.[(3)H]GA(1) was identified by combined gas-liquid chromatography/mass spectrometry as a major product of [(3)H]GA(20), and was found to be a more potent promoter of tobacco callus growth than GA(20).