Internode length in Lathyrus odoratus. The involvement of gibberellins

Evidence was obtained by gas chromatography‐mass spectrometry and gas chromatography‐selected ion monitoring for the presence of gibberellin A 20 ), GA 1 , GA 29 , GA 8 and 2‐epiGA 29 in vegetative shoots of tall sweet pea, Lathyrus odoratus L. Both tall (genotype L –) and dwarf (genotype II ) sweet peas elongated markedly in response to exogenous GA 1 attaining similar internode lengths at the highest dose levels. Likewise internode length in both genotypes was reduced by application of the GA biosynthesis inhibitor, PP333. The ratio of leaflet length to width was reduced by application of PP333 to tall plants and this effect was reversed by GA 1 . When applied to plants previously treated with PP333, GA 20 promoted internode elongation of L – plants as effectively as GA 1 , but GA 29 was not as effective as GA 1 when applied to II plants. In contrast, GA 20 and GA 1 were equally effective when applied to the semidwarf lb mutant but GA‐treated lblb plants did not attain the same internode length as comparable GA‐treated Lb – plants. The difference in stature between the tall and dwarf types persisted in dark‐grown plants. It is concluded that GA 1 may be important for internode elongation and leaf growth in sweet pea. Mutant l may influence GA 1 synthesis by reducing 3β‐hydroxylation of GA 20 whereas mutant lb appears to affect GA sensitivity.