tailieunhanh - Báo cáo khoa học: "The role of photoperiod and temperature in the induction and the release of dormancy in Pinus sylvestris L. seedlings"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài:"The role of photoperiod and temperature in the induction and the release of dormancy in Pinus sylvestris L. seedlings. | 228s Ann. Sci. For. 1989 46 suppl. 228s-232s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA The role of photoperiod and temperature in the induction and the release of dormancy in Pinus sylvestrís L. seedlings I. Dormling Swedish University of Agricultural Sciences Department of Forest Genetics Stockholm Sweden Introduction Scots pine Pinus sylvestris L. seedlings exhibit optimal development during their first growth period if given 25-20 C during the daytime and 15-10 C nighttime temperature. Optimal night length is 6-8 h depending upon latitude of origin 67-57 N. Longer as well as shorter nights bring about early bud set. Buds are formed sooner or later under all growing conditions Dormling 1975 . The buds formed during short nights are not stable however. Several flushes may occur if the night length is not prolonged. Weaka of growth in 25 15 c 4 h night before prolong. Night prolong until Percent plants with after growth in 20 new shoots 10 mm ght weeks 1 o c. 6h ni during BD 4 the following 2054 1 umber of H 4 1019 6 8 6 8 13h 3 3 7 1 6h 3 13h CD CD 3 3 1 2 1 6h 0 3 0 3 Fig. 1. BD 2064 67 45 N and H 1019 57 25 N. Flushing rate in 2nd growth period. Night prolongation 1 h wk in 25 5 C started at plant age 7 and 12 wk and stopped after the wk with 13 and 16 h respectively n 16. 229s 25 5 C 25 15 C low temperature treatment 2 w 5 C - 4 w 2 C - 2 w 5 0 À low temperature treatment 1 w 5 c - 2 w 2 C - 1 w 5 c without low temperature treatment Fig. 2. w 4107 60 41 N. Flushing rate in 2nd growth period. Plants raised in 25 15 c with 6 and 4 h nights. Night prolongation in 25 5 C and 25 15 c. Dormancy breaking treatment at 8 4 and 0 wk. n - 10. There are indications that Scots pine buds do not overwinter in a stage of true dormancy Dormling et al. 1977 Kupila-Ahvenniemi 1985 . Seedlings exposed to long nights for 4-7 wk produce buds that flush readily after exposure to growing conditions. More than 20 cycles with long nights completely change the growth .