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 regi on of E. globulus (Labill.), then analysed by capillary gas chromatogr aphy-mass spectrometry. GA1, GA19, GA20 and GA29 were identified by fu ll scan mass spectra, Kovats retention indices and high resolution sel ected ion monitoring. Using deuterated internal standards, GA1, GA19, GA20 and putative GA29 and GA53 Were quantified in the apical buds, wh ile GA4, GA8, GA9 and GA44 were shown to be either absent or present a t very low levels. From the cambial region, GA1 and GA20 were quantifi ed 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 pa thway is the dominant pathway for GA biosynthesis in Eucalyptus.