Timing and duration of short-day treatment influence morphology and second bud flush in Picea abies seedlings

Short-day photoperiods affect expression of genes related to dormancy and freezing tolerance in Norway spruce seedlings

“…Similar results were obtained by Dormling et al (1968), Dormling (1973Dormling ( , 1979Dormling ( , 1993, Ekberg et al (1979), Konttinen et al (2003Konttinen et al ( , 2007, Kohmann and Johnsen (2007), as well as Fløistad and Granhus (2013). Activity of dormancy-related genes as identified by Stattin et al (2011) indicated that the seedlings in our study need at least 14 days of SD treatment, corresponding to a photoperiod of 11 h for dormancy induction.…”

“…Several studies suggest that less than 2 weeks of SD treatment is enough to terminate apical shoot growth (Dormling et al 1968;Heide 1974;Konttinen et al 2003;Fløistad and Granhus 2013). Our results indicate that 7 days of SD treatment is as effective as longer SD treatments to stop apical shoot growth.…”

“…Our results indicate that 7 days of SD treatment is as effective as longer SD treatments to stop apical shoot growth. Further, other provenances of Norway spruce than used in this study as well as different starting dates of SD treatment could affect seedling shoot growth patterns (see, e.g., Fløistad and Granhus 2013). Outdoor-grown control seedlings of the local provenance of Norway spruce used for this experiment still exhibited some shoot elongation as late as the third week of September indicating that the seedlings Seedlings had been subjected to SD (short day) treatments (11 h light; 13 h night) of various lengths starting on July 15, 2013 and thereafter kept indoors or outdoors.…”

“…This suggests that different provenances will respond variably to different timing and durations of SD treatments. Fløistad and Granhus (2013) showed that SD treatment (7,10,14, and 17 days) of Norway spruce (origin 60°N, 10°E) significantly affected height growth after just 7 days of treatment. Their results among others also suggest that Norway spruce seedlings require a longer SD treatment to avoid a second bud flush, especially if the treatment starts early (Heide 1974;Granhus 2010, 2013;Luoranen and Rikala 2015).…”

“…The intensity and duration of SD treatments vary widely across regions and nurseries, but typically fall within a range of 8-12 h of photoperiod for 14-35 days (Rosvall-Åhnebrink 1982; Konttinen et al 2003;Jacobs et al 2008;Luoranen et al 2009;MacDonald and Owens 2010;Fløistad and Granhus 2013). SD treatment promotes early growth cessation and induces bud set (Dormling et al 1968;Heide 1974;Ekberg et al 1979;Colombo et al 1989Colombo et al , 2001Fløistad and Granhus 2013), while also increasing seedling freezing tolerance (Dormling 1982;Colombo et al 1989Colombo et al , 2001Jacobs et al 2008). Thus, this cultural treatment is now regularly employed in container nurseries across Canada and Scandinavia in production of boreal conifers (Colombo et al 2001).…”