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.

Réponse germinative des graines de l’aulne glutineux et du bouleau pubescent à l’application d’acide gibbérellique et de traitements d’amorçage en combinaison avec du froid

“…• C. Thus the TMC seeds are also likely to better withstand the stresses of handling and storage than the FI seeds, in agreement with earlier findings [9,10]. This may not be surprising because seeds are known to deteriorate less rapidly at low MC than at high MC levels [29].…”

“…Seeds of these species can be adjusted to about 30−35% MC and then chilled for 12−18 weeks to release dormancy and maximise germination speed [9]. Seeds adjusted to these 'target' MC (TMC) levels can be held at chilling or freezing temperatures for lengthy periods without the risk of premature germination [9,10]. A combination of GA 3 and chilling at TMC levels might increase germination potential while reducing the risk of premature germination in alder and birch seeds.…”

Development of cryopreservation methods for cherry birch (Betula lentaL.), an endangered tree species in Canada

“…In vitro germination rates ranged from 0 to 50% depending on the medium used. Relatively low germination of cherry birch seeds in this study may have resulted from storage conditions at 4°C or may be related to seed dormancy which has been previously reported for Betula species (Chmielarz 2010a;De Atrip and O'Reilly 2006).…”

Cryopreservation of conditionally dormant orthodox seeds of Betula pendula

“…Freezing at -12°C of fully imbibed seeds of B. pubescens reduced seed germination (De Atrip and O'Reilly 2006), but moisture content of 15% (0.16 g g 21 ) for B. pendula seeds is safe to store its seeds at -70°C (Schönborn 1964). This moisture content (0.16 g g 21 ) fits within the safe range of WC (0.02-0.23 g g 21 ) determined for seeds frozen in LN.…”