| Abstract: | The main purpose of these studies was to investigate the adaptation of young seedlings of various seed lots of Picea abies (L.) Karst., P. glauca (Moench) Voss, P. x lutzii Little and P. sitchensis (Bong.) Carr. to northern climatic conditions. Effects of temperature and photoperiod on elongation growth and growth cessation were studied under controlled conditions in a phytotron. In addition, growth and survival of the seedlings outdoors at 69°39’ N lat. were followed for two years. Seed lots of /’. abies originated from northern Norway (66° N lat.), those of the other species were from Alaska (between 57°.and 66° N lat.). The critical photoperiod for budset was 19–20 h for seed lots of P. abies. In general, the critical photoperiod for budset increased with increasing latitude of the seed source, but the results indicated a significantly shorter cirtical photoperiod for seed lots from about 60° N lat., <120 m a.s.l. of P. sitchensis (between 12 and 16 h) than for comparable seed lots of P x lutzii (17–18 h) or P. glauca (18 h). The time course of budset under natural light conditions, both in the phytotron and outdoors, generally followed the pattern predicted from the critical photoperiod. However, in P. glauca the budset occurred earlier than in P. abies although the latter had a longer critical photoperiod. Due to the short critical photoperiod and consequently delayed growth cessation and hardening, all seed lots of P. sitchensis (from 58° to 60° N lat.) were severely damaged during winter. Some damage was also observed in P. x lutzii and in P. abies. The optimum temperature for elongation growth was higher for P. sitchensis than for the other species. In the phytotron experiments, seedlings of P. sitchensis grew best at temperatures between 12 and 21°C, but at 9°C the best growth was obtained in some seed lots of P. abies. After two growth seasons outdoors, all seed lots of P. abies were taller than any seed lot of the other species. Also P. glauca seed lots and one seed lot of P. x lutzii showed good growth, and their growth rhythm seemed to be well adapted to the northern conditions. |
