Development and growth of primordial shoots in Norway spruce buds before visible bud burst in relation to time and temperature in the field.

The climate in the northern boreal zone is characterized by strong seasonal variation in temperature and light conditions. In order to survive, the trees face the unfavourable winter period in a frost hardy dormant state, so that a period of active growth and one of dormancy alternate in their annual cycle (Weiser 1970, Sarvas 1972, 1974, Fuchigami et al. 1982). It is essential that the changes from the susceptible active growth state to the frost hardy dormant state and back are properly synchronized with the seasonal temperature variation. Therefore, the annual physiological rhythm of trees is regulated by interaction between genetic and environmental factors. Research paper