© 1997 Heron Publishing—Victoria, Canada
Relationship between temperature, respiratory loss of sugar and premature dehardening in dormant Scots pine seedlings
Erling Ögren
Department of Plant Physiology, Umeå University, S-901 87 Umeå, Sweden / Received February 28, 1996
Summary
Increased intracellular sugar concentration is an important contributor to the increased cold tolerance of conifers in winter.
This study examines the extent to which wintertime respiratory loss of sugars leads to premature dehardening. Two-year-old
seedlings of Scots pine (Pinus sylvestris L.), grown and cold-hardened in the field, were exposed to different temperature regimes for 16 weeks while dormant. To minimize
short-term carry-over effects, after the temperature treatments, all seedlings were conditioned to 5.5 °C and watered before
the assessment of non-structural carbohydrates and cold tolerance. Needle sugar concentration was decreased by 54, 32, 21
and 9% following treatment at 5.5, 0, –1.5 and –8.5 °C, respectively. Sugar concentration did not decrease as much in root
tissues as in needles because starch was mobilized in roots. Cold tolerance of needles was analyzed by controlled freezing,
and the temperature causing an initial 10% damage (LT10) was plotted as a function of needle sugar concentration, revealing a strong, linear relationship. When one-third of the
initial sugars had been consumed, LT10 had increased from –24.5 to –16.5 °C, and when one half had been consumed, LT10 had increased to –10 °C. Consequences of these findings for the field performance of conifers are discussed in relation to
climatic variation and change.
Keywords:
carbohydrate, climate change, cold tolerance, Pinus sylvestris, respiration, winter damage.
