Internode length in Pisum. IV. The effect of the Le gene on gibberellin metabolism

Abstract

The highly active, polar gibberellin‐like substance found in the apical region of shoots of tall (genotype Le) peas (Pisum sativum L.) is shown by combined gas chromatography‐mass spectrometry (GC/MS) to be GA1. This substance is either absent or present at only low levels in dwarf (le) plants. Multiple ion monitoring (MIM) tentatively suggests that GA8 may also be present in shoot tissue of tall peas. Gibberellin A1 is the first 3 β‐hydroxylated gibberellin positively identified in peas, and its presence in shoot tissue demonstrates the organ specificity of gibberellin production since GA1 has not been detected in developing seeds. Application of GA1 can mask the Le/le gene difference. However, whilst Le plants respond equally to GA20 and GA1, le plants respond only weakly to GA20, the major biologically active gibberellin found in dwarf peas. These results suggest that the Le gene controls the production of a 3 β‐hydroxylase capable of converting GA20 to GA1. Further support for this view comes from feeds of [3H] GA20 to Le and le plants. Plants with Le metabolise [3H] GA20 to three major products whilst le plants produce only one major product after the same time. The metabolite common to Le and le plants co‐chromatographs with GA29. The additional two metabolites in Le peas co‐chromatograph with GA1 and GA8.