© 1995 Heron Publishing—Victoria, Canada
Seasonal variation in photochemical activity and hardiness in clones of Norway spruce (Picea abies)
Johan Westin (1), Lars-Göran Sundblad (1) and Jan-Erik Hällgren (2)
1. The Forestry Research Institute of Sweden, P.O. Box 3, S-918 21 Sävar, Sweden / 2. Department of Forest Genetics and Plant Physiology, Faculty of Forestry, Swedish University of Agricultural Sciences, S-901
Umeå, Sweden / Received date not available
Summary
We investigated changes in photochemical activity and cold hardiness of detached needles of three clones of Picea abies (L.) Karst. by measuring variable chlorophyll fluorescence (Fv/Fm), before and after artificial freezing, from September to June. Photochemical activity varied considerably during the study,
but only minor differences in photochemical activity among the clones were observed before freezing. Photochemical activity
was high during early fall and then declined from November until April. Photochemical activity was at a minimum in April and
then increased quickly to high values in May.
During the period from late September to October, and also during the winter, differences in Fv/Fm ratios after artificial freezing to below –10 °C were observed among clones, indicating clonal differences in cold hardiness
and hardiness development. The clone having an average height of 2.3 m after 11 years showed consistently lower cold hardiness
than clones that had reached average heights of 4.0 and 5.0 m. There were also differences in the temperature requirement
for bud flushing among clones.
Keywords:
chlorophyll fluorescence, winter stress.
