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

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The role of photoperiod and temperature in the induction and the release of dormancy in Pinus sylvestris L. seedlings I. Dormling Swedish University of Agricultural Sciences, Department of Forest Genetics, Stockholm, Sweden Introduction depending upon latitude of origin, 67-57°N. Longer as well as shorter nights bring about early bud set. Buds are form- Scots pine (Pinus sylvestris L.) seedlings ed sooner or later under all growing condi- exhibit optimal development during their tions (Dormling, 1975). The buds formed first growth period if given 25—20°C during during short nights are not stable, how- the daytime and 15-10°C nighttime tem- Several flushes may if the ever. occur perature. Optimal night length is 6-8 h, night length is not prolonged.
1977; Dormling, 1986). The normal winter There are indications that Scots pine dormancy of Scots pine, however, buds do not overwinter in a stage of true includes a rest phase which is broken by dormancy (Dormling et al., 1977; Kupila- exposure to cold (Romberger, 1963). The Ahvenniemi, 1985). Seedlings exposed to necessity to fulfill the chilling requirement long nights for 4-7 wk produce buds that to break winter dormancy in Scots pine flush readily after exposure to growing has been stressed (e.g., Wareing, 1951; conditions. More than 20 cycles with long Vegis, 1965; Sarvas, 1974). nights completely change the growth habit In the following,I will use the working from the juvenile stage with primary needles to the stage with needle fascicles definition of dormancy proposed by Lang (1987): &dquo;Dormancy is the temporary sus- secondary needles (Dormling et al., =
different temperature used regimes as a was Seedlings dormancy inducing treatment. were grown in pots with mineral wool as a substrate and watered daily with a low concentration nutrient solution: 2L 6513, 100 mg N/I (Inge- stad, 1979). Light was provided by Osram HQI lamps, irradiance ca 80 W- (400-700 nm) at 2 - M plant level. The air humidity was 75% RH. Results and Discussion Fig. 1 illustrates that seedling age at the start of night prolongation, 7 or 12 wk, an important role in the possibility played of the buds to attain a deeper stage of dormancy. Only the 12 wk old plants of northern origin had no flushing buds after 6 wk under growing conditions. These seedlings had their most dormant buds after 13 h nights. They lost some dorman- cy during the further prolongation to 16 h. Short night length, 4 h, during growth made the seedlings more dormant after night prolongation for more than the 6 h night - the optimal one for height growth (Fig. 2). The same was true for the higher temperature 25/15°C compared with of viable of any plant pension growth 25/5°C. Dormancy breaking treatments of meristem.&dquo; True containing structure a 8 and 4 wk had a dramatic influence, dormancy, i.e., a stage in which growth is hastening the tilushing rate, especially in not possible even under the most favo- the plants with lowest degree of dormancy. rable conditions, may not exist (Vegis, In Fig. 3 the same reactions to tempera- 1965). For that reason, deep dormancy ture and break of dormancy are illustrated will be used as the definition of the most by height increment curves for seedlings dormant stage obtained. There are no of southern origin. strict borderlines to phases before and which had relatively short Seedlings after deep dormancy. Early and late nights, 6 h, during the first growth period phases of dormancy are characterized as produced in the 2nd period stems with quiescence: dormancy imposed by the long distances between the needle fas- external environment (Romberger, 1963). cicles long stem units (Fig. 4). The 8 h = seedlings had a denser appearance. In- Materials and Methods dependent of the initial night length, plants given the longest dormancy breaking Seedlings of Scots pine of different Swedish ori- treatment had the longest shoots in the gins were raised in the Stockholm Phytotron. 2nd growth period. This was not accompa- Day temperature was 25’C, night temperature nied by longer stem units, however. Ins- 15°C, night length as indicated in the figure tead the plants formed more stem units. legends. Night prolongation with 1 h per wk in
Dormling 1. (1986) Dormancy in Scots pine Conclusions (Pinus sylvestris L.) seedlings. In: Prove- nances and Forest Tree Breeding for High Lati- All conditions provided during seedling tudes. (Lindgren D., ed.), Dept. For. Genet. development may influence its later Plant Physiol. Swedish Univ. Agric. Sci., Umeil, Rep. 6, pp. 81-98 degree of bud dormancy. Deepest dor- Dormling I., Eriksson G. & Jonsson A. (1977) mancy is reached after a long growth pe- Photo- and thermoperiodic reactions of Pinus riod with short night followed by night pro- sylvestris and Pinus contorta. (Swedish with longation with high temperature. Low English summary) In: Experimental Genecolo- +5°C, is effective in temperature, +2 to gy, Stockholm 1977. Dept. For. Genet. R. Coll. breaking dormancy of any stage. The Stockholm, Res. Notes 27, pp. 48-57 For. deeper the dormancy, the longer the time (1979) Mineral nutrient require- T. Ingestad sylvestris and Picea abies seed- ments of Pinus needed for a complete break. lings. Physiol. Plant. 45, 373-380 chan- Kupila-Ahvenniem S. (1985) Wintertime ges in the fine structure and the ribosome content of the buds of Scots pine. In: Plant References Production in the North. (Kaurin A., Junttila O. & Nilsen J., eds.), Norway University Press. pp. Dormling 1. (1975) Photo- and thermoperiodic 171-180 reactions in Scots pine seedlings can they - Lang A.G. (1987) Dormancy: a new universal provide criteria for an early test? (Swedish with terminology. Hortic. Sci. 22, 817-820 English summary) In: Transfer of Scots pine Romberger J.A. (1963) Meristems, growth, and (Pinus sylvestris L.) seed. Dept. For. Genet. R. development in woody plants. U.S. Dept. Coll. For. Stockholm Res. Notes 17, pp. 125- 4 Agric. For. Ser. Tech. Bull. 1293, pp. 214 140
Sarvas R. (1974) Investigations on the annual uebersicht, terminologie, ailgemeine probleme. cycle of development in forest trees. II. Autumn PfIanz XV, 499-533 nphysiol. 6 Handb. and winter dormancy. Commun. dormancy Wareing P.F (1951) Growth studies in woody tn!f. For. Fenn. 84, 1 -101 species ill. Further photoperiodic effects in Vegis A. (1965) Ruhexustande bei h6horen pflanzen, induktion. verfaut und beendigung: Pinus sylvestr!s: Ph!sm/. Plant. 4, 41-56