CONJUGATED POLYAMINES AND FLOWERING DIFFERENTIATION IN THE DOUGLAS-FIR (PSEUDOTSUGA-MENZIESII (MIRB.) FRANCO)

To characterize as early as possible the status of flowering different iation in Douglas-fir (Pseudotsuga menziesii (Mirb.) France), the vari ation of bound or conjugated polyamines is studied in the shoots of yo ung plants (6 years old) during the period covering flowering initiati on (between 30 and 75 days after bud burst). These compounds are also quantified in sexual and vegetative buds. The quantitative effects of treatments susceptible to stimulate the flowering (application of gibb erellins and (or) calcium nitrate) on the level of conjugated polyamin es are investigated in the shoots. The combination of gibberellins to calcium nitrate application strongly increases the flowering. Conjugat ed polyamines are particularly abundant in sexual buds and in the shoo ts of flowering plants. Sexual buds are also characterized by a ratio of conjugated putrescine to conjugated spermidine about four to six ti mes higher than in vegetative buds. The accumulation of conjugated pol yamines in the shoots accompanies bud sexualization, which suggests th at conjugated polyamines may constitute potential markers of floral in itiation in Douglas-fir.