Jouni Partanen, Risto Häkkinen, Anneli Viherä-Aarnio, Niina Stenvall, Heikki Hänninen. (2026). Short-day treatment in late summer reduces the chilling requirement in Norway spruce seedlings. Silva Fennica vol. 60 no. 2 article id 25053. https://doi.org/10.14214/sf.25053

Keywords: bud burst percentage; days to bud burst; rest; endodormancy release; forcing, quiescence

Highlights: Short-day treatment reduces the chilling requirement and the time to bud burst in Norway spruce seedlings; Forcing photoperiod does not affect the time to bud burst of short-day treated seedlings; In natural outdoor conditions, the short-day treatment advances the bud burst slightly.

Abstract | Full text in HTML | Full text in PDF | Author Info

Artificial shortening of photoperiod with short-day (SD) treatment in late summer is a common measure in forest nurseries to advance the growth cessation and increase the frost hardiness of seedlings in the autumn. We conducted an experimental study of the effect of SD treatment (12 h) in the preceding summer and the photoperiod (16 h, 8 h) prevailing in the regrowth test under forcing conditions. The effect of these factors on the chilling requirement in second-year Norway spruce Picea abies (L.) Karst. seedlings was studied. Half of the seedlings were first subjected to a three-week SD treatment between 11 July and 1 August 2005, whereas the other half were used as the control group. The seedlings were first exposed to chilling in natural conditions. Subsequently, samples of the seedlings were transferred at intervals between September and May to a regrowth test in growth-promoting forcing conditions in a greenhouse. Additionally, we observed the bud burst of the seedlings in natural conditions during the next spring. Our main result was that SD treatment reduced the chilling requirement in the seedlings. Long photoperiod (16 h) in the forcing conditions also reduced the chilling requirement. The buds of the SD-treated seedlings burst earlier than those of the control seedlings and generally at almost the same time in both photoperiods. This suggests that the photoperiod prevailing in the forcing conditions has no additional delaying or advancing effect on the bud burst of SD-treated seedlings. In natural outdoor conditions, the SD treatment in the preceding summer advanced the springtime bud burst slightly.

Partanen, Natural Resources Institute Finland (Luke), Production Systems, Juntintie 154, FI-77600 Suonenjoki, Finland https://orcid.org/0009-0007-1782-4283 E-mail: ext.jouni.partanen@luke.fi
Häkkinen, Natural Resources Institute Finland (Luke), Production Systems, P.O. Box 2, FI-00791 Helsinki, Finland https://orcid.org/0009-0007-1687-1045 E-mail: risto.hakkinen@yahoo.com
Viherä-Aarnio, Natural Resources Institute Finland (Luke), Production Systems, P.O. Box 2, FI-00791 Helsinki, Finland https://orcid.org/0000-0002-1777-637X E-mail: annelivihe@outlook.com
Stenvall, Natural Resources Institute Finland (Luke), Production Systems, P.O. Box 2, FI-00791 Helsinki, Finland https://orcid.org/0000-0002-9447-8712 E-mail: niina.stenvall@luke.fi
Hänninen, State Key Laboratory for Development and Utilization of Forest Food Resources, Zhejiang A&F University, 666 Wusu Street, Hangzhou 311300, PR China https://orcid.org/0000-0003-3555-2297 E-mail: hhannin@zafu.edu.cn

Category : Research note

article id 1443, category Research note

Jouni Partanen, Risto Häkkinen, Heikki Hänninen. (2015). Significance of the root connection on the dormancy release and vegetative bud burst of Norway spruce (Picea abies) seedlings in relation to accumulated chilling. Silva Fennica vol. 50 no. 1 article id 1443. https://doi.org/10.14214/sf.1443

Keywords: phenology; bud burst percentage; days to bud burst; dormancy release; forcing

Highlights: Cutting the root connection slightly increased the number of days to bud burst of Norway spruce seedlings under warm conditions but it had no consistent effect on bud burst percentage; Our results obtained with seedlings suggest that using detached tree material in dormancy release experiments may slightly affect the results but it will evidently not lead to drastically erroneous conclusions.

Abstract | Full text in HTML | Full text in PDF | Author Info

The effect of cutting the root connection by detaching the shoot from the root system on dormancy release and vegetative bud burst was examined in 2-year-old seedlings of Norway spruce (Picea abies [L.] Karst.). Seedlings were transferred at 1–4 week intervals between October and January from outdoor conditions to experimental forcing in a heated greenhouse. Before forcing, half of the seedlings were cut above ground line, and the detached shoots were forced with their cut ends placed in water. The intact seedlings were forced with their root system remaining intact in the pots. Vegetative bud burst was observed visually. Cutting the root connection slightly increased days to bud burst in the forcing conditions, however, no consistent effect on bud burst percentage was found. Our preliminary seedling data suggest that using detached tree material in dormancy release experiments may have a small effect on bud burst date but it will evidently not lead to drastically erroneous conclusions. Further studies, using different seed lots, are needed to assess the effect of detaching on the dormancy release and bud burst, especially in adult trees.

Partanen, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: jouni.partanen@luke.fi
Häkkinen, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: risto.hakkinen@luke.fi
Hänninen, University of Helsinki, Department of Biosciences, Viikki Plant Science Centre (ViPS), P.O. Box 65, FI-00014 University of Helsinki, Finland E-mail: heikki.hanninen@helsinki.fi

article id 608, category Research note

Jouni Partanen, Ilkka Leinonen, Tapani Repo. (2001). Effect of accumulated duration of the light period on bud burst in Norway spruce (Picea abies) of varying ages. Silva Fennica vol. 35 no. 1 article id 608. https://doi.org/10.14214/sf.608

Keywords: Norway spruce; phenology; growth initiation; photoperiod

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One-year-old seedlings (two sowing times), two-year-old seedlings and 14- and 18-year-old cuttings of Norway spruce (Picea abies (L.) Karst.) were exposed to shortening photoperiod (initially 16 h), lengthening photoperiod (initially 6 h) and constant short photoperiod (6 h) treatments with uniform temperature conditions in growth chambers. The timing of bud burst was examined. In all plants, shortening photoperiod treatment seemed to promote bud burst compared with other treatments. This effect was clearest in the oldest material. The results suggest that, in addition to temperature sum, the accumulated duration of the light period may promote bud burst of Norway spruce.

Partanen, Finnish Forest Research Institute, Punkaharju Research Station, Finlandiantie 18, FIN-58450 Punkaharju, Finland E-mail: jouni.partanen@metla.fi
Leinonen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: il@nn.fi
Repo, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: tr@nn.fi

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