Endogenous Gibberellins from Sporophytes of Two Tree Ferns, Cibotium glaucum and Dicksonia antarctica

Abstract

Gibberellin A₁ (GA₁), 3-epi-GA₁, GA₄, GA₉, 11α-hydroxyGA₁₂, 12α-hydroxyGA₁₂, GA₁₅, GA₁₇, GA₁₉, GA₂₀, GA₂₅, GA₃₇, GA₄₀, GA₅₈, GA₆₉, GA₇₀, and GA₇₁ have been identified from Kovats retention indices and full scan mass spectra by capillary GC-MS analyses of purified extracts from sporophytes of the tree fern, Cibotium glaucum. Abscisic acid, dihydrophaseic acid, an epimer of 4′-dihydrophaseic acid, and the epimeric ent-6α, 7α, 16α, 17-(OH)₄ and ent-6α, 7α, 16β, 17-(OH)₄ derivatives of ent16, 17-dihydrokaurenoic acid, in addition to the epimeric 16α, 17- and 16β, 17-dihydroxy-16, 17-dihydro derivatives of GA₁₂, were also identified in extracts of C. glaucum. An oxodihydrophaseic acid and a hydroxydihydrophaseic acid were also detected. In extracts of sporophytes of Dicksonia antarctica, GA₄, GA₉, 12α- and 12β-hydroxyGA₁₂, GA₁₅, GA₂₅, and GA₃₇ were identified by the same criteria, as well as abscisic acid, phaseic acid, 8′-hydroxymethylabscisic acid and dihydrophaseic acid. This is the first time that GA₄₀ has been identified in a higher plant; it is also the first report of the natural occurrence of the two gibberellins, 11α- and 12β-hydroxyGA₁₂. The total gibberellin (GA) content in C. glaucum (tall) was at least one order of magnitude greater than that of D. antarctica (dwarf) based on total ion current response in GC-MS and bioassay data. Abscisic acid was a major component of D. antarctica and the oxodihydrophaseic acid was a major component of C. glaucum.