CHANGES IN AMINO-ACIDS AND POLYAMINES IN SHOOTS AND BUDS OF DOUGLAS-FIR TREES INDUCED TO FLOWER BY NITROGEN AND GIBBERELLIN TREATMENTS

To characterize as early as possible the status of flowering different iation in Douglas-fir (Pseudotsuga menziesii (Mirb.) France), the vari ation of amino acids and polyamines was studied in the shoots during t he period covering flowering initiation (between 4 and 10 weeks after bud burst). These compounds were also quantified in sexual and vegetat ive buds. The qualitative and quantitative effects of treatments susce ptible to stimulate flowering (application of gibberellins (GA) and (o r) calcium nitrate (N)) were observed in the shoots. Only N and N + GA treated trees flowered, the flowering being especially abundant for t rees treated by N + GA. Arginine and proline were generally more abund ant in sexual buds than in vegetative ones and in the shoots of flower ing plants than in the control shoots. Sexual buds were characterized by a ratio of putrescine/(spermidine + spermine) about two times lower than in vegetative buds, mainly owing to a lower level in putrescine. The accumulation of polyamines in the shoots accompanied bud sexualiz ation, which suggests that polyamines may constitute potential markers , probably rather early ones (4-6 weeks after bud burst), of floral in itiation in Douglas-fir. This possibility is discussed.