Abstract
To examine the after-effects of low storage temperatures and elevated growing temperatures on flower-bud initiation and flowering in freesia, corms of 'Elegance' were potted and chilled at 2°C for 6, 8 and 10 weeks, 5°C for 5 and 6 weeks, or 8°C for 3.5 and 4 weeks. The chilled corms, which were at the stages just before or after flower-bud initiation at the end of chilling, were grown at 22/18°C or 26/22°C (day/night). Although the shoot apex was vegetative at the end of the chilling period and growing at 26/22°C was excessively warm for flower-bud initiation, only 30% of the corms chilled at 2°C for 10 weeks, initiated flower buds after differentiating several leaves and flowered. At 22/18C, those corms which received chilling treatments had not yet initiated flower buds at the end of the chilling period, but, nevertheless, all flowered earlier with smaller number of leaves than non-chilled plants. These results indicate that low temperature vernalizes corms, thus, promotes flower-bud initiation and flowering. When corms were potted, chilled at 5°C for 4 and 5 weeks, were subjected to 30/26°C for 1∼3 weeks at stages before flower-bud initiation, and subsequently grown at 22/18°C, the vernalizing effect of chilling was completely cancelled by 30/26°C treatment. The reversal indicates that high temperature exposure just after chilling has a devernalizing effect. The promoting effect of flower-bud initiation given by chilling was continued by subjecting plants to 18/14°C for 3 weeks or longer before they were grown at 26/22°C. We conclude from our results that exposing freesia corms to temperatures between 2 and 5°C has a vernalizing effect, whereas exposing the chilled corms to high temperature, albeit a short period, has a devernalizing effect.
