Internode length in <i>Pisum</i>. IV. The effect of the <i>Le</i> 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 GA 1 . This substance is either absent or present at only low levels in dwarf ( le ) plants. Multiple ion monitoring (MIM) tentatively suggests that GA 8 may also be present in shoot tissue of tall peas. Gibberellin A 1 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 GA 1 has not been detected in developing seeds. Application of GA 1 can mask the Le/le gene difference. However, whilst Le plants respond equally to GA 20 and GA 1 , le plants respond only weakly to GA 20 , 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 GA 20 to GA 1 . Further support for this view comes from feeds of [ 3 H] GA 20 to Le and le plants. Plants with Le metabolise [ 3 H] GA 20 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 GA 29 . The additional two metabolites in Le peas co‐chromatograph with GA 1 and GA 8 .