Breaking seed dormancy in European rowan seeds and its implications for regeneration

The effects of the presence of a medium, seed moisture content, warm and chilling treatments on the germination response of European rowan (Sorbus aucuparia L.) seeds of Irish origin were investigated with the aim of reducing precocious (or premature) germination and maximising germination after pretreatment. After adjusting seed moisture content, seeds of two lots were subjected to warm treatment for 0-6 weeks followed by 0-50 weeks of chilling. The seeds then were allowed to germinate at a constant 15 A degrees C with 8 h lighting per day or 20 (dark)/30 A degrees C (light). Some seeds were treated in the fully imbibed (FI) state in a medium (standard operational treatment). Seed lot effects were evident, but treatment effects were consistent in each lot. Warm treatment greatly increased germination and reduced precocious germination. The presence of a medium was not required to achieve high germination and seed moisture content close to the FI state was needed to maximise germination. Climate change may reduce the ability of this species to regenerate naturally, favouring other species that require less chilling.