The response of prechilled alder and birch seeds to drying, freezing, and storage

Abstract

The response of alder (Alnus glutinosa (L.) Gaertn.) and birch (Betula pubescens Ehrh.) seeds to freezing temperatures was assessed. Seeds were fully imbibed (FI) or adjusted to target moisture contents (TMC) of 30% (alder) or 35% (birch) and then chilled (4 °C) for various periods. Some seeds were redried to <12% moisture content before freezing. The seeds were germinated at 15 °C with 8 h of lighting after freezing. In the first experiment, rapid freezing at –12 °C was used to assess seed vigour. Freezing reduced percentage germination in the moist (non-redried) FI seeds, especially in those that received the longest prechilling. Freezing had a smaller effect on the TMC and the redried seeds. In the second experiment, seeds were stored for up to 60 weeks at –3 °C. Seeds stored for 60 weeks were tested also at 20 °C (16 h dark) : 30 °C (8 h light). Good germination potential was maintained for up to 12 weeks of storage regardless of pretreatment, but it declined rapidly thereafter in the moist FI seeds. Moist TMC seeds maintained good germination potential throughout the 60 weeks of storage. Germination potential declined greatly following 24 weeks of storage in the redried seeds, but the redried seeds germinated well at 20 °C (16 h dark) : 30 °C (8 h light) following 60 weeks of storage.