Changes in amino acids and polyamines in shoots and buds of Douglas-fir trees induced to flower by nitrogen and gibberellin treatments

Abstract

To characterize as early as possible the status of flowering differentiation in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), the variation of amino acids and polyamines was studied in the shoots during the period covering flowering initiation (between 4 and 10 weeks after bud burst). These compounds were also quantified in sexual and vegetative buds. The qualitative and quantitative effects of treatments susceptible to stimulate flowering (application of gibberellins (GA) and (or) calcium nitrate (N)) were observed in the shoots. Only N and N + GA treated trees flowered, the flowering being especially abundant for trees treated by N + GA. Arginine and proline were generally more abundant in sexual buds than in vegetative ones and in the shoots of flowering 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 sexualization, which suggests that polyamines may constitute potential markers, probably rather early ones (4–6 weeks after bud burst), of floral initiation in Douglas-fir. This possibility is discussed.