© 1998 Heron Publishing—Victoria, Canada
Effects of photoperiod and temperature on the timing of bud burst in Norway spruce (Picea abies)
Jouni Partanen (1), Veikko Koski (2) and Heikki Hänninen (3)
1. Finnish Forest Research Institute, Punkaharju Research Station, FIN-58450 Punkaharju, Finland / 2. Finnish Forest Research Institute, Vantaa Research Center, PB 18, FIN-01301 Vantaa, Finland / 3. University of Joensuu, Faculty of Forestry, PB 11, FIN-80101 Joensuu, Finland / Received August 26, 1997
Summary
We examined the effects of several photoperiod and temperature regimes imposed during the winter–spring period on the timing
of bud burst in rooted cuttings of Norway spruce (Picea abies (L.) Karst.) grown in a greenhouse in Finland. The treatments were initiated in November and December after the cuttings
had been exposed to natural chilling and freezing events. Irrespective of the treatments applied, time to bud burst decreased
with increased duration of previous exposure to natural chilling and freezing events. Fluctuating day/night temperatures and
continuous lengthening of the photoperiod hastened bud burst. Shortening the photoperiod delayed bud burst, suggesting that
little or no ontogenetic development toward bud burst takes place during mild periods before the winter solstice. In the case
of climatic warming, this phenomenon may prevent the premature onset of growth that has been predicted by computer simulations
with models that only consider temperature regulation of bud burst.
Keywords:
climate change, phenology, premature onset of growth.
