Shoot elongation in Lathyrus odoratus L.: Gibberellin levels in light- and dark-grown tall and dwarf seedlings.

The levels of gibberellin A1 (GA1), GA20, GA19, GA8, GA29 and GA81 (2-epiGA29) were measured in tall (L-) and dwarf (ll) sweet-pea plants grown in darkness and in light. In both environments the apical portions of dwarf plants contained less GA1; GA8 and GA19, but more GA20, GA29, and GA81 than did those of tall plants. It is concluded that the partial block in 3β-hydroxylation of GA20 to GA1 is imposed by allele l in darkness as well as in the light. Furthermore, darkness does not appear to enhance elongation in sweet pea by increasing GA1 levels. The reduction of the pool size of GA19 in dwarf plants supports recent theories on the regulation of GA biosynthesis, formulated on the basis of observations in monocotyledonous species. Darkness results in decreased GA20, GA29, and GA81 levels in the apical portions of tall and dwarf plants and possible reasons for this are discussed.