Genetic and environmental contributions to the winter hardiness of conifers

Summary

Both genetic and environmental components are involved in the processes of winter hardening and dehardening which permit needles of conifers like Norway spruce to survive very low temperatures (< - 30°C) over winter and to recover fully in time for the following and subsequent seasons. One of the major environmental effects of increasing concentrations of atmospheric ozone (O₃) in recent summers has been to affect detrimentally the ability of conifer needles to harden properly and at the correct rate the following autumn. Part of the mechanism by which this occurs in the cytoplasm of needle cells has been traced to detrimental effects on both the Δ¹² fatty acid desaturase and the unusual Δ⁵ desaturase which appears to be part of the low temperature survival mechanism of conifers. The genetic component of winter hardening also involves needle lipids. Studies of lipids in the needles of Norway spruce trees of different provenances growing for many years in the UK have shown that they change during winter hardening as though they were still on trees in the original sites throughout Europe from which the seeds of these trees were initially collected.