2011 Volume 10 Issue 1 Pages 75-80
To promote flowering of Primula × polyantha Mill., cold storage was applied to seedlings in continuous darkness. When the seedlings of three cultivars were chilled to 0°C for 30 days till the end of August, all but the early cultivar flowered earlier. The seedlings of ‘Seventy Blight Pink’ were chilled to 0, 5, or 10°C for 15 or 30 days. Flower bud differentiation of the seedlings chilled to 10°C occurred earlier than that of those chilled to 0°C. The seedlings chilled to a higher temperature for a longer duration flowered earlier. However, their leaf widths and flower diameters were small when the seedlings were chilled to 10°C for 30 days. The seedlings chilled till the end of August flowered normally although a high proportion of those chilled till the end of July failed to show normal flowering. Based on these findings, it was considered optimal for the seedlings to be chilled to 0°C for 30 days till the end of August. Furthermore, the seedlings flowered earlier than those chilled to 0°C for 4 weeks without showing any decrease in leaf width, when they were chilled in a temperature combination of 0°C for 1 week and 10°C for 3 weeks, or they were chilled to 10°C for 4 weeks after foliar application of daminozide (1,600 ppm).
