QUANTITATION OF GIBBERELLINS A(9), A(1) AND A(3) IN RELATION TO FLOWER BUD DIFFERENTIATION IN PICEA-ABIES

Endogenous gibberellin A(1) (GA(1)), GA(3), GA(4) and GA(9) were quant itated in elongating shoots of Norway spruce [Picea abies (L.) Karst.] grafts with a good or a poor flowering history. The grafts were grown either in a natural environment outdoors, cool and wet (CW) treatment , or in a greenhouse with elevated temperatures and controlled drought stress, hot and dry (HD) treatment. The GAs were quantitated by gas c hromatography-mass spectrometry selected ion monitoring (GC-MS SIM) us ing deuterated GA(1), GA(3), GA(4) and GA(9) as internal standards. Te rminal shoots from the second whorl of branches were harvested at 76%, 86% and 96% shoot elongation for the CW treated grafts and at 90% and 99% shoot elongation for the HD treated grafts. The content of GAs in the CW grafts was highest during most rapid shoot elongation, GA(9) b eing the dominant GA. The levels decreased as shoot elongation ceased. This was also noted for GA-content in shoots of the HD treated grafts . A comparision of the GA-amounts at ca. 96% of total shoot elongation for the CW treated grafts and ca. 99% of total shoot elongation for t he HD treated grafts revealed that shoots of the good flowering clone had a higher content of GA(9) and a lower content of GA(1) and GA(3). When comparing the HD treated and CW treated grafts, the shoots of HD treated grafts contained higher concentrations of GA, but lower concen trations of GA(1) and GA(3). Calculating the ratios between [GA(9)] an d [GA(1)] resulted in a ratio of 12.5 and 36.6 for the good flowering clone grown outdoors and in greenhouse, respectively. The same ratios were for the poor flowering clone 1.45 and 3.8 when grown outdoors and in greenhouse, respectively. A higher ratio may indicate a higher cap acity of synthezise the importance of flowering GA(4) from GA(9) and a lower conversion of GA(4) to GA(1), thereby favouring the diffentiati on to reproductive buds.