Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Changes in endogenous cytokinins during flowering induction in Douglas fir: effect of exogenous applications N. Imbault. | 40s Ann. Sci. For. 1989 46 suppl. 40s-43s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Changes in endogenous cytokinins during flowering induction in Douglas fir effect of exogenous applications N. Imbault1 p. Doumas2 c. Joseph1 and M. Bonnet-Masimbert2 1 Laboratoire des Composes Phénoliques Université d Orleans 45067 Orleans Cedex and 2 INRA Station d Amelioration des Arbres Forestiers Ardon 45160 Olivet France Introduction The involvement of plant growth substances PGS in flowering promotion in conifers was analyzed in relation to the level of gibberellins Pharis ef al. 1987 . However in herbaceous species cytokinins are sometimes considered as one of the components which promote flowering Bernier at al. 1977 Lejeune eta . 1988 . In Douglas fir some treatments such as fertilization stem girdling root pruning or root flooding can favor flowering Bonnet-Masimbert 1982 . Roots are also considered to be the major site of cytokinin synthesis Kende 1964 . Endogenous cytokinins were analyzed in Douglas fir initially in the sexual buds and then in the shoots during floral differentiation. Then the observed changes in the compound assimilated to isopentenyladenine iP led to the study of an effect of this compound on flowering. Materials and Methods O-uai buds of Douglas fir Pseudotsuga i were collected from file same 10 yr old tree in April during the time of bud development . Shoots were collected from 5 yr old ramets of the same clone. They were subjected to different treatments at the time of bud burst 1 control 2 stem perfusion of an aqueous solution of gibberellins A4 7 plus naphthyl acetic acid 3 alternate root flooding 2 1 2 d in water and 2 1 2 d out for 3 wk 4 combination of treatments 2 and 3. Shoots were collected 3 and 6 wk after bud burst. Exogenous ÍP was applied to shoots of 6 yr old trees. Cytokinin bases and ribosides were extracted and analyzed as described by Imbault et al. 1988 . Cytokinin nucleotides were extracted with 10 .
