Internode length in <i>Pisum</i>. III The effect and interaction of the <i>Na/na</i> and <i>Le/le</i> gene differences on endogenous gibberellin‐like substances

Abstract

In the garden pea ( Pisum sativum L.), shoots of the extremely short plants with the mutant na (phenotype nana) are found by bioassay to contain undetectable levels of gibberellin‐like substances. This is confirmed by the use of near isogenic lines differing at the Na locus. Thus, mutant na appears to block a step early in the pathway of gibberellin synthesis. It is suggested that the polar gibberellin‐like substance found in the apical portion of shoots of tall ( Le ) but not dwarf ( le ) peas could be GA 1 . Extracts of shoots of na Le peas treated with GA 20 (the major active gibberellin in dwarf peas) possess a large amount of GA 1 ‐like activity whereas extracts of shoots of na le peas treated with GA 20 possess a much reduced amount. Thus, gene Le may allow the conversion of a less active gibberellin (GA 20 ) into one more active in stimulating elongation in the pea (the GA 1 ‐like compound). In contrast to their influence in the shoot, the na and Le genes do not appear to be operative in controlling the gibberellin content of developing seed, indicating that organ specific gibberellin biosynthesis and metabolism occur in peas.