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. | 47s Ann. Sci. For. 1989 46 suppl. 47s-50s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Field experiment on the effect of girdling and gibberellin application on flowering induction of 12 yr old seedlings of Douglas fir and Norway spruce M. Bonnet-Masimbert with the technical assistance of G. Chanteloup p. Delanzy and J. Coupaye INF A Station dAmélioration des Arbres Forestiers Ardon 45160 Olivet France Introduction Climate has a strong influence on flowering of trees and for field experiments it is difficult to control environmental conditions. Thus many experiments on flowering induction in conifers are performed on potted trees which are at least partly maintained under greenhouse conditions. The benefits of establishing indoor orchards instead of classical soil-based ones have been proposed. However hundreds of hectares of soil-based seed orchards have been established and must be managed for a more abundant and regular flowering. Also besides clonal orchards generally grafted some seedling seed orchards have been established which for an equivalent size are less mature than grafts. This paper deals with preliminary field experiments on Douglas fir Pseudotsuga menziesii and Norway spruce Picea abies seedlings. Materials and Methods Two experiments using combinations of bark girdling G double semicircular overlapping 5 mm wide girdles and trunk injections of gibberellins GA4 7 were tested in 1986 on 12 yr old seedlings 6-8 m high raised in the INRA Orleans nursery. Douglas fir 50 seedlings belonging to 7 open-pollinated families were divided among 4 treatments applied just before vegetative bud burst 1 control 2 girdling 3 girdling 50 mg GA4 7 45 A7 5 mg naphthalene acetic acid NAA 4 girdling 100 mg GA4 7 10 mg NAA. At treatment time each tree received soil fertilization with 200 g of Ca NO3 2. GA4 7 injections were made in 300 pl of ethanol in the xylem of the 1981 internode. On each tree 4 branches on both the 1982 and 1984 whorls were selected .
