Báo cáo lâm nghiệp: Changes in endogenous cytokinins during flowering induction in Douglas fir: effect of exogenous applications N. Imbau

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Báo cáo lâm nghiệp: "Changes in endogenous cytokinins during flowering induction in Douglas fir: effect of exogenous applications N. Imbau"Changes in endogenous cytokinins during floweringinduction in Douglas fir: effect of exogenous applications M. Bonnet-Masimbert 2 P. Doumas 2N. Imbault C. Joseph1 Laboratoire des Composes Ph6noliques, Universite d’Orl6ans, 45067 Orl6ans Cedex, and2 INRA, Station dAmelioration des Arbres Forestiers, Ardon, 45160 Olivet, France tree in the time of ’budIntroduction April during develop- ment’. Shoots were collected from 5 yr old ramets ofThe involvement of plant growth sub- the same clone. They were subjected to dif-stances (PGS) in flowering promotion in ferent treatments at the time of bud burst:conifers was analyzed in relation to the 1) control; 2) stem perfusion of an aqueous solution of gibberellins A plus naphthyl acetic 4nlevel of gibberellins (Pharis et al., 1987). acid; 3) alternate root flooding (2 1/2 d in waterHowever, in herbaceous species, cyluki- and 2 1/2 d out) for 3 wk; 4) combination ofnins are sometimes considered as one of treatments 2 and 3. Shoots were collected 3the components which promote flowering and 6 wk after bud burst.(Bernier 2 1977; Lejeune et al., 1988). t al., Exogenous iP was applied to shoots of 6 yr old trees.In Douglas fir, some treatments, such as Cytokinin bases and ribosides were extractedfertilization, stem girdling, root pruning or and analyzed as described by Imbault et al.root flooding, can favor flowering (Bonnet- (1988). Cytokinin nucleotides were extractedMasimbert, 1982). Roots are also conside- with 10°f° perchloric acid, purified on a cellulosered to be the major site of cytokinin phosphate column and on a carboxylic acid column before separation by high performancesynthesis (Kende, 1964). Endogenous cy- liquid chromatography (HPLC) using an aniontokinins were analyzed in Douglas fir, ini- exchange column Partisil 10 SAX (Whatman)tially in the sexual buds and then in the to separate the mono-, di- and triphosphateshoots during floral differentiation. Then, cytokinins, and a C18 column (Beckman Ultra-the observed changes in the compound spher, 5 pm) to separate the compounds of the zeatin family from those from the iP family inassimilated to isopentenyladenine (iP) led the monophosphate zone (Laloue, personalto the study of an effect of this compound communication). Cytokinins cochromatograph- flowering.on ing with standards and which were recognized by antibodies directed against isopentenyla- denosine (iPA) or ribosylzeatin (RZ) were quan- tified by radioimmunoassay.Materials and Methods In another experiment, iP was exogenously applied. The modalities consisted of the appli- cation of 3 quantities of iP (0, 0.5, 5 !ig): 2 types uai’; bods oí Douglas fir (Pseudofsuga men- from 1he same 10 yr old of solvent (ethanol or water with 0.05% Aromox !ir 11;>d . ’1C); 2 zones of application (distal 1l3 or proximal Results2/3 of the shoot); 2 dates of application (3 or 6wk after individual bud burst). The following Cytokinin bases and ribosides were ana-spring, male and female strobili were countedon each shoot. ...