Inhibition of growth of microcultured Hancornia speciosa shoots by 3β-hydroxylated gibberellins and one of their C-3 deoxy precursors

Abstract.

Gibberellins (GAs) A₁, A₃, A₄ and A₇, all 3β-hydroxylated, growth-active GAs, significantly inhibited shoot elongation and the formation of nodes in in vitro-grown Hancornia speciosa, as did GA₂₀, a 3-deoxy precursor of GA₁. Ancymidol, an early-stage inhibitor of GA biosynthesis, significantly retarded shoot elongation without affecting the formation of nodes. Co-application of ancymidol and GA₁ did not overcome the ancymidol-induced growth retardation. Trinexapac-ethyl, which can inhibit 3β-hydroxylation (GA activation) and 2β-hydroxylation (GA inactivation), gave no significant response on either shoot elongation or node formation, while two isomers of 16,17-dihydro GA₅, also inhibitors of GA 3β-hydroxylation, significantly inhibited both shoot growth and the formation of nodes. These unusual results may indicate a unique metabolism for GAs in microcultured shoots of H. speciosa.