Identification and quantification of endogenous gibberellins in apical buds and the cambial region of Eucalyptus

Endogenous gibberellins (GAs) were extracted and purified from apical buds of Eucalyptus nitens (Deane and Maid.) Maid. and the cambial region of E. globulus (Labill.), then analysed by capillary gas chromatography-mass spectrometry. GA₁, GA₁₉, GA₂₀ and GA₂₉ were identified by full scan mass spectra, Kovats retention indices and high resolution selected ion monitoring. Using deuterated internal standards, GA₁, GA₁₉, GA₂₀ and putative GA₂₉ and GA₅₃ Were quantified in the apical buds, while GA₄, GA₈, GA₉ and GA₄₄ were shown to be either absent or present at very low levels. From the cambial region, GA₁ and GA₂₀ were quantified at levels of 0.30 ng (g fresh weight)^-1 and 8.8 ng (g fresh weight)^-1 respectively. These data suggest that the early 13-hydroxylation pathway is the dominant pathway for GA biosynthesis in Eucalyptus.