The effect of time of corm lifting and duration of incubation at inductive temperature on flowering in the saffron plant ( Crocus sativus L.)

Abstract

After the formation of the replacement corms of saffron ( Crocus sativus L.) the leaves withered and the apical buds entered dormancy. This dormancy was released by high summer temperature. Optimal flower formation was obtained under controlled conditions when corms were held at 25 °C longer than 55 days followed by forcing at 17 °C. Since the shoot apical meristem of the replacement corms was formed long before leaf withering, it was feasible to accelerate flowering by an early harvest. Corms lifted 1 month before leaf withering, incubated for 55 days at 25 °C, and then forced at 17 °C, flowered by early September, 6 weeks earlier than in the open. Flowering could be further accelerated (up to 7 days) by curing the corms for 20 days at 30 °C prior to 25 °C storage. This high temperature incubation shortened the rest period of the buds. However, a longer exposure to 30 °C was deleterious for bud growth and flower formation. A 24 h incubation with ethylene (1–10 ppm) had no effect on dormancy or flower formation. The flowering of corms lifted after leaf withering could be delayed until early December by extending the incubation at 25 °C for 150 days. A longer incubation at 25 °C resulted in flower abortion. Combining the date of corm lifting and the duration of 25 °C incubation, corms could be flowered from early September to mid-December. Since a batch of corms needed an average of 13 days in a lighted greenhouse at 17 °C to complete flowering, 7–8 batches of corms may be forced each growing season. At the corm density used in our experiments (457 corms m −2), 67.2 g of the spice saffron per square meter was obtained. This yield was 30 times higher than the maximum yield reported under field conditions, and about 300-fold higher than the average yield in many saffron-producing regions. Furthermore, the harvest of the container-grown saffron may be easily mechanised.