%0 Research article
%T Seed moisture content during chilling and heat stress effects after chilling on the germination of common alder and downy birch seeds
%A O'Reilly, Conor
%A De Atrip, Norberto
%D 2007
%J Silva Fennica
%V 41
%N 2
%R doi:10.14214/sf.293
%U https://silvafennica.fi/article/293
%X The effects of seed moisture content (MC) and heat treatment on the  germination response of common alder (Alnus glutinosa) and downy birch  (Betula pubescens) seeds were examined. Seeds of each species were  adjusted to MC of 7% to 50% MC, then chilled for up to 36 weeks, after  which they were allowed to germinate at 15°C with 8 hours lighting per  day or 20 (dark)/ 30°C (light). Seed lot effects were evident, but  treatment effects were consistent in each lot and species. The response  to moist chilling treatments was larger at 15°C than at 20/30°C.  Chilling had no effect on germination unless seed MC was >15%, but it  was low also at 20% MC. The highest germination was achieved following  24–36 weeks chilling at the optimum or target MC (TMC) levels of about  30% in alder and 35% in birch. In a separate experiment, seeds were  fully imbibed (FI) (~50% MC; standard method used in operational  practice) or adjusted to TMC levels, after which some seeds of each  treatment group were chilled to release dormancy. Following this, the  seeds were dried back to TMC levels and then subjected to 60°C for up to  4 hours after which they were allowed germinate under the same  conditions described above. Heat treatment damaged the prechilled FI  seeds, but no damage occurred to the non-chilled seeds. However, heat  stress stimulated germination in the non-chilled FI seeds of both  species and the TMC seeds of alder.