Seed maturation in pollination bags influences the timing of terminal bud set of Norway spruce seedlings

Controlled crosses were made on clones in a seed orchard and the pollination bags were kept on the branches until the cones were harvested. Cones after open pollination were collected at the same time. Seedlings from the controlled pollinations, from open pollination of the same maternal parent and from commercial provenances were grown in growth chambers and terminal bud set was recorded after short day treatments. The seedlings from the seeds of cones that were kept in the pollination bags had a significantly later bud set then expected based on comparisons with their half-sibs from open pollination. The difference corresponds to a decrease in altitude of 100 m at provenance level. It can be caused by epigenetic effects due to temperature differences inside and outside the bags during seed maturation.