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

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Changes in endogenous cytokinins during flowering induction in Douglas fir: effect of exogenous applications M. Bonnet-Masimbert 2 P. Doumas 2 N. Imbault C. Joseph 1 Laboratoire des Composes Ph6noliques, Universite d’Orl6ans, 45067 Orl6ans Cedex, and 2 INRA, Station dAmelioration des Arbres Forestiers, Ardon, 45160 Olivet, France tree in the time of ’bud Introduction April during develop- ment’. Shoots were collected from 5 yr old ramets of The 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 4n level of gibberellins (Pharis et al., 1987). acid; 3) alternate root flooding (2 1/2 d in water However, in herbaceous species, cyluki- and 2 1/2 d out) for 3 wk; 4) combination of nins are sometimes considered as one of treatments 2 and 3. Shoots were collected 3 the 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 extracted fertilization, stem girdling, root pruning or and analyzed as described by Imbault et al. root flooding, can favor flowering (Bonnet- (1988). Cytokinin nucleotides were extracted Masimbert, 1982). Roots are also conside- with 10°f° perchloric acid, purified on a cellulose red to be the major site of cytokinin phosphate column and on a carboxylic acid column before separation by high performance synthesis (Kende, 1964). Endogenous cy- liquid chromatography (HPLC) using an anion tokinins 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 triphosphate shoots 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 in assimilated to isopentenyladenine (iP) led the monophosphate zone (Laloue, personal to 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 . ’1
C); 2 zones of application (distal 1l3 or proximal Results 2/3 of the shoot); 2 dates of application (3 or 6 wk after individual bud burst). The following Cytokinin bases and ribosides were ana- spring, male and female strobili were counted on each shoot. lyzed in the sexual buds. Male and female
buds presented the same peaks, corre- sponding to the iP, iPA, zeatin and RZ retention times. There was a supplemen- tary peak before the RZ one in the female buds; this peak has not yet been identi- fied. We did not observe any differences in forms of the monophosphate nucleo- tides. They had the same retention time peaks as RZ monophosphate, dihydro- zeatin monophosphate and iPA mono- phosphate standards (Fig. 1This uni- dentified peak had neither the same retention time as the iPA monophosphate standard nor that of the iP or the iPA stan- dard but it reacted with the anti-iPA anti- bodies. It could correspond to another form of cytokinin nucleotides. Bases and ribosides also were ana- lyzed in Douglas fir shoots during floral differentiation after induction by different treatments. Only the iP-iPA zone is pre- sented. Fig. 2a shows the results of com- pounds cochromatographing with iPA. The quantities of iPA were not related to the flowering or to the treatment. Compounds cochromatographing with iP are repre- sented in Fig. 2b. Like iPA, no relation could be established between the treat- ments and the iP rate; but there seemed to be a relationship between the iP rate and female flowering. In other iP experiment, exogenous our to shoots to confirm its pos- applied was sible effect flowering. iP had no signifi- on cant effect on male flowering (Fig. 3a) but it had a positive effect on female flowering (Fig. 3b) at the highest dosage (5 J1 per g shoot) and in the early treatments (3 wk after bud burst), given at a time when floral differentiation could occur (Owens, 1969). r!- ’&dquo; r-u__...- -I...1...- a:«----. --a-,:.:-- -I. :- ---,:--
(Mirb.) Franco. Silvae Genet. 21, 178- Conclusion menziesii 188 lmbault N., Tardieu I., Joseph C., Zaerr J.B. & Besides gibberellins and probably some Bonnet-Masimbert M. (1988) Possible role of other PGS, iP may be one of the compo- isopentenyladenine and isopentenyladenosine in flowering of Pseudotsuga menziesii: endo- nents involved in hormonal regulation of genous variations and exogenous applications. flower promotion in Douglas fir. However, Plant Physiol. Biochem. 26, 289-295 it is certainly not the only one and these Kende H. (1964) Preservation of chlorophyll in results will be compared later to those leaf sections by substances obtained from root obtained with other PGS in the same exudates. Science 163, 1066-1067 shoots. Lejeune P., Bernier G. & Kinet J.M. (1988) Cytokinin fluxes during floral induction in the long day plant Sinapis alba L. Plant Physiol. 86, 1095-1098 References Owens J.N. (1969) The relative importance of initiation and early development on cone pro- duction in Douglas fir. Can. J. Bot. 47, 1030- Bernier G., Kinet J.M., Jacmard A., Havelange 1049 I. & Bodson M. (1977) Cytokinin as a possible component of a floral stimulus in Sinapis alba. Pharis R.P., Webber J.E. & Ross S.D. (1987) Plant Physiol. 60, 282-285 The promotion of flowering in forest trees by gibberellin A4/7 and cultural treatments: a Bonnet-Masimbert M. (1982) Influence de 1’6tat review of the possible mechanisms. For. Ecol. d’activit6 des racines sur la floraison induite par les gibberellines 4 et 7 chez Pseudotsuga Manage. 19, 65-84