Báo cáo lâm nghiệp: "experiment on the effect of girdling and gibberellin application on flowering induction of 12 yr old seedlings of Douglas fir and Norway spruce"

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Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: experiment on the effect of girdling and gibberellin application on flowering induction of 12 yr old seedlings of Douglas fir and Norway spruce...

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Nội dung Text: Báo cáo lâm nghiệp: "experiment on the effect of girdling and gibberellin application on flowering induction of 12 yr old seedlings of Douglas fir and Norway spruce"

experiment on the effect of girdling and gibberellin Field application on flowering induction of 12 yr old seedlings of Douglas fir and Norway spruce M. Bonnet-Masimbert with the technical assistance of G. o Chanteloup, P. Delanzy and J. Coupaye INRA, Station damdlioration des Arbres Forestiers, Ardon, 45160 Olivet, France .. - I...-- - I..- ...... I ..1 ! mm wide girdles) and trunk injections of gib- Introduction berellins (GA4/7) were tested in 1986 on 12 yr old seedlings, 6-8 m high, raised in the INRA Climate has a strong influence on flow- (Orl6ans) nursery. ering of trees and, for field experiments, it is difficult to control environmental condi- Douglas fir tions. Thus, many experiments on flow- 50 seedlings, belonging 7 open-pollinated to ering induction in conifers are performed divided among 4 treatments families, were on potted trees, which are at least partly applied just before vegetative bud burst: 1) maintained under greenhouse conditions. control; 2) girdling; 3) girdling + 50 mg GA4/7 The benefits of establishing indoor (45% A7) + 5 mg naphthalene acetic acid (NAA); 4) girdling + 100 mg GA4/7 + 10 mg orchards instead of classical soil-based NAA. At treatment time, each tree received soil ones have been proposed. However, fertilization with 200 g of Ca(N0 GA4/7 . 2 ) 3 hundreds of hectares of soil-based seed injections were made in 300 pl of ethanol in the orchards have been established and must xylem of the 1981 internode. On each tree, 4 branches on both the 1982 and 1984 whorls be managed for a more abundant and were selected for shoot measurement and cone regular flowering. Also, besides clonal counts. Two branches were plastic-bagged (in orchards (generally grafted), some seed- order to simulate a localized ’greenhouse ling seed orchards have been established effect’) for 2 wk starting 3 wk after the beginning which, for an equivalent size, are less of the treatment. mature than grafts. This paper deals with preliminary field experiments on Douglas Norway spruce fir (Pseudotsuga menziesii) and Norway open-pollinated 30 seedlings, belonging to 6 spruce (Picea abies) seedlings. were divided families, among 5 treatments. applied when about 50% of Treatments were the lateral shoot elongation was completed and consisted of: 1) girdling; 2) girdling + 2 x 50 mg Materials and Methods GA4/7 at a 2 wk interval in the 1983 internode; applied in the 1981 treatment 2 3) same as application of 100 internode; 4) girdling + one Two experiments using combinations of bark mg GA4/7 in the 1983 internode; 5) same as girdling (G) (double semicircular overlapping 5
applied in the 1981 internode. and female flowering. On the other hand, treatment 4 GA4/7 injections were made in 300 pl of etha- GA4/7 increased the length of both nol. On each tree, 4 branches (in the 4 cardinal terminal and subterminal shoots. The directions) on both 1983 and 1984 whorls were higher whorl produced significantly more selected for shoot measurement and cone female cones but, curiously, this was also counts, 2 of them were plastic-bagged for 4 wk, starting at the beginning of treatments. true for male cones. Bagging the shoot slightly reduced terminal elongation but length of the terminal and 2 subterminal The measured in the fall on each se- shoots were had no effect on flowering. Finally, all 3 lected branch and their total number of male treatments differed significantly from the and female cones were counted the following control for the mean total number of fe- spring on the entire branch. Also, the total num- male cones per tree. ber of female cones on the entire tree was counted. On each sampling branch, terminal and subterminal shoot elongation and number of male and female cones were subjected to variance analysis (see the text for the analyzed Norway spruce factors) and Duncan’s test. The family effects here. presented not are The main results are summarized in Table II. All the trees were girdled, but treatment 1 alone only slightly stimulated flowering Results and Discussion compared to (aA + girdling treatments. Therefore GA4/7 had a specific and signi- ficant effect on both male (only for 1 injec- fir Douglas tion of 100 mjj GA4/7) and female flow- best results corresponding to 2 ering (the The main results are given in Table I. Gir- injections of 50 mg GA4/7, (treatments 2 dling with or without GA4/7 had a strong and 3). This differential sexual response significant stimulatory effect on both male may be related to differences in the dif- I u, 1&dquo;&dquo;;1,1,.
ferentiation period between both sexes. Conclusion Higher branches typically bore more fe- male cones. Differences also existed in It is possible to stimulate the flowering of the proportion of shoot elongation com- seedlings of Norway spruce (mainly fe- pleted at treatment time (60.3 and 79% for male) and Douglas fir in the field through a terminal and subterminal shoots of the combination of girdling and GA4/7 treat- lower whorl as opposed to 48.6 and 67% ments. GA4/7 is confirmed to be especial- for the higher whorl, respectively). Even if ly necessary for Norway spruce (Bonnet- female flowering of Norway spruce was Masimbert, 1987). Certainly these positive generally located at the very top of the due to the fact that partly were responses tree, these differences in elongation might favorable to natural 1986 was generally also be related to a stage of vegetative flowering induction. From comparisons development in the higher whorls more between the last 5 yr, we suspect that high favorable for flowering induction (Bonnet- sunshine from mid-June to the beginning Masimbert, 1987). of July may have a positive effect. Kosin- For the total number of female cones ski and Giertych (1982) clearly demon- strated the role of light intensity on flow- per tree (Table 11) there is no significant difference between the 4 GA4/7 treat- ering of Norway spruce. However, growth ments. In contrast to the observations on response of 1986-girdled Douglas fir in Douglas fir, GA4/7 often reduced the 1987 and 1988 was reduced. Further- shoot elongation in spruce significantly. more, bud-burst was delayed for 1-2 wk Plastic bagging caused a slight but signifi- over the control, indicating a durable cant reduction in the elongation of the ter- physiological stress. So, contrary to the minal shoot. It had no significant effect on results of Wheeler et aL, (1985), girdling male or female flowering or elongation of can hardly be proposed as a routine treat- subterminal shoots. ment in soil-based seed orchards.
Kosinski G. & Giertych M. (1982) Light condi- References tions inside developing buds affect floral induc- tion. Planta 155, 93-94 Bonnet-Masimbert M. (1987) Preliminary results Wheeler N.C., Masters C.J., Cade S.C., Ross gibberellin induction of flowering of seedlings S.D., Keeley J.W. & Hsin L.Y (1985) Girdling: on and cuttings of Norway spruce indicate some an effective and practical treatment for en- carry-over effects. For. E!1. Manage. 19, 163- hancing seed yields in Douglas fir seed orchards. Can. J. For. Res. 15, 505-510 171 0