Responses of Norway spruce seedlings to different night interruption treatments in autumn

Abstract

Photoperiodic lighting can be used in late summer to prevent height growth cessation and terminal bud formation in nurseries growing forest tree species in Nordic countries. To create guidelines for using the method in container nurseries growing Norway spruce (Picea abies (L.) Karst.) and to test the use of light-emitting diode (LED) technology, we exposed first-year, nursery grown seedlings to the following night interruption (NI) treatments from 10 July 2014 onwards (00:00–03:00): (i) no lighting, (ii) 1 min lighting at intervals of 30 min, (iii) 1 min lighting at intervals of 15 min, and (iv) 3 h continuous lighting. Light intensities (LI) of 10, 25, and 70 μmol photosynthetically active radiation (PAR) m−2·s−1 were used. Growth, formation of terminal buds, and winter damage of the seedlings were measured. All NI treatments prevented growth cessation at LI of 25 and 70 μmol PAR·m−2·s−1, but the intermittent treatments were less effective at a LI of 10 μmol PAR·m−2·s−1. The treatments of duration longer than 1 min at intervals of 30 min did not provide any additional increase in shoot growth but predisposed the seedlings to frost injury during autumn and winter. Both seed origins used in this experiment responded similarly to the NI treatments.