Effects of Temperature on Flowering of Sternbergia lutea Roem. & Schult

In this study, the growth periodicity of Sternbergia plants grown outdoors was clarified and the effect of temperature on the initiation and development of flower buds was investigated.1. The Sternbergia bulb develops a sympodial branching system. Each unit has about 8 foliage leaves and terminates in 2 or 3 inflorescences. The bases of the foliage leaves, except the uppermost leaf, encircle the vertical axis of the bulb and gradually enlarge into scales which serve as food storage organ.2. Floret initiation on the primary inflorescence occurs between April and early May. Carpel primordia are visible in early July and the pollen tetrad are formed in early September. Anthesis occurs in late September. Floral differentiation on secondary and tertiary inflorescences follows that of the primary inflorescence after a short delay.3. Flower initiation occurs at temperatures between 10°and 30°C, but the optimum range was 20°-25°C. Once initiated, floral differentiation and development progressed most rapidly at 25°-30°C.4. The development of flower bud from carpel formation stage to flowering was faster at 20°-25°C than at 30°C. At 10°C flower buds ceased to develop and became blasted.5. Bulbs kept at 20°C after July 1, when the main inflorescence attained the carpel formation stage, bloomed earlier but produced fewer inflorescences as compared to those placed at 25°or 30°C from July 1 to August 19 and thereafter shifted to 20°C. This result suggests that bulbs should be kept at 25°-30°C after carpel formation in the main inflorescence to optimize the development of secondary and tertiary inflorescences.6. To retard development of flower bud until the Christmas season, bulbs were stored at 5°and 30°C after August 20. Bulbs stored at 30°C and planted in late November flowered in late December when forced in a glasshouse kept above 20°C, but those stored at 5°C did not flower because the flower buds became blasted.