WARM-FOLLOWED-BY-COLD STRATIFICATION OF MOUNTAIN-ASH (SORBUS AUCUPARIA L.) SEEDS

Preceding cold stratification by a warm period of up to 32 weeks had no effect on total germination when it was already high without this warm period. In contrast, when cold stratification resulted in low germination, an initial warm phase lasting 6 or more weeks, considerably increased total germination percent. In all cases, the warm pretreatment significantly shortened germination period, this shortening being proportional to the duration of the warm phase. The onset of germination in the cold phase was usually delayed by the application of the initial warm phase.

Temperature of the warm phase had little effect on seed germination during the cold phase. In contrast, temperature of the cold phase significantly influenced germination. Duration of the germination period was longer at 5° than at 1° or -3°C, regardless of the duration of the preceding warm phase. The delay of the onset of germination caused by the warm phase was also greatest at 5°C. The warm pretreatment was more effective when the subsequent cold phase occured at 1° or 3°, than when it took place at 5°C.

Most synchronized germination of seed population of S. aucuparia was obtained by startification at 1° or 3°C preceded by 10 weeks at 15–25°C. When seeds pretreated in this way until the onset of germination were sown in the field at the end of March, seedlings emerged in up to 80% in the first spring.

Download Adobe Acrobat Reader (free software to read PDF files)