Doctoral thesis, 2018
From growth cessation to bud burst - conifer seedling development in response to nursery culture and environmental stimuliWallin, Elisabeth
AbstractIn Sweden, 350-400 million seedlings are produced annually for forest regeneration. About one third of these are overwintered in frozen storage, necessitating accurate methods to assess storability. Young transplants of Norway spruce (Picea abies (L.) Karst.) intended for short-term frozen storage were considered storable before reaching target levels for safe storage using shoot dry matter content, freezing tolerance and the molecular test ColdNSure™. Results also indicated that using shoot dry matter content for storability assessment can be misleading, not only for Norway spruce but also for Scots pine (Pinus sylvestris (L.)). Post-storage vitality can easily and rapidly be determined by measuring the electrolyte leakage from shoots (SEL) of pine and spruce seedlings. SEL and regrowth tests showed that the vitality of young transplants decreased when the time in storage was prolonged from 3-4 to 5-7 months. Short-day (SD) treatment of seedlings shortens the time for dormancy induction and makes seedlings storable at an earlier date. The activity level of dormancy related genes, and genes associated with freezing tolerance reflects the effect of different treatments e.g., the importance of combining longer periods of SD treatment (21-28 days) with low temperature exposure to rapidly obtain storable seedlings. Gene expression profiles have the potential to be used for assessment of seedling dormancy status, predict the development of freezing tolerance, bud set, the risk for a second bud flush in autumn and the timing of bud burst in spring. The interest in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) has increased in Sweden. Frost risks in spring make bud burst timing important when selecting suitable provenances of Douglas-fir for planting. A field trial and a greenhouse study showed the same pattern concerning time of bud burst for a number of Douglas-fir provenances, indicating that greenhouse screening tests can be used for provenance selection. Considering bud burst patterns together with previously reported winter hardening characteristics the interior provenance Three Valley would have a good chance of successful field establishment in southern Sweden.
KeywordsPicea abies, Pinus sylvestris, Pseudotsuga menziesii, seedling status, gene activity, photoperiod, storability, vitality, transplants, shoot electrolyte leakage
Published inActa Universitatis Agriculturae Sueciae
2018, number: 2018:12
ISBN: 978-91-7760-164-7, eISBN: 978-91-7760-165-4
Publisher: School for Forest Management, Swedish University of Agricultural Sciences