Effects of KNO3 pretreatment and temperature on seed germination of Sorbus pohuashanensis

We characterized the effects of KNO₃ pretreatment and germination temperature on dormancy breaking and germination of mature mountain ash seeds. Seeds treated with KNO₃ and germinated at 25 °C followed by 5 °C had significantly higher germination percentages and germination potentials (51% and 49%, respectively), compared with controls. These treated seeds also exhibited reduced germination initiation times (minimum of 48 days), and elevated germination rate indices (up to 97). The germination of seeds subjected to long-term cold storage (2 years at 0–5 °C) was also significantly improved by 3 days of 4% KNO₃ pretreatment before germinating under a variable temperature regimen (5 °C followed by 25 °C, and followed by 5 °C). Germination percentages and germination potentials for these cold-stored seeds reached 67% and 54%, respectively, and the germination rate index increased to 126.99. Pretreatment of mountain ash seeds with KNO₃ represents a practical, effective, and pollution-free method for improving germination, and can be implemented easily within a variety of nursery settings.