2000 Volume 69 Issue 1 Pages 115-117
Corms of Freesia hybrida Hort. 'Cote d'Azur' averaging 6.7g, which had been stored at 30°C for 10 weeks, were potted, exposed to seven temperature classes from 3 to 21°C for 6 weeks and then transferred to 23°C. Flower buds were observed microscopically at the end of exposure to 6, 9, 12, 15, and 18°C. The developmental stage of flower buds was most advanced at 12 and 15°C ; however, the flower buds initiated at 12, 15, and 18°C failed to develop floral parts, and the elongation of the flower stalks was greatly suppressed upon transfer to 23°C. Whereas, plants exposed to 9°C for 6 weeks consequently flowered at 23°C ; those exposed to 6°C developed malformed inflorescences having abnormally elongated bracts and lacking floral organs. At 23°C, the apical meristems of plants exposed to 3°C continued to initiate leaf primordia, while those exposed to 21°C formed bract-like organs. Daughter corm formation 10 weeks after transferring plants to 23°C was most advanced in plants previously exposed to 12°C for 6 weeks. Three directional effects of chilling : 1) direct effect on flower bud initiation, 2) after-effect on flower bud development and flower stalk elongation, and 3) direct effect and/or after-effect on corm formation, are discussed.
