Effect of Chilling at Germinating Stage on the Flowering Response of Pharbitis nil Choisy

Abstract

The response of flowering to chilling was examined using germinating seed of Pharbitis nil Choisy, strain Kidachi grown in pots. Flowering occurred when the germinating seed was chilled immediately after sowing at 15°C for longer than 25 days. The flowering response decreased if plants were grown at higher temperatures after the chilling. Young seedlings 1 to 4 day old showed a strong response to chilling, while the flowering response decreased in the seedlings chilled at increasing ages from 6 to 10 day old. Application of gibberellin A₃ to the seedling promoted the flowering response, suggesting that endogenous gibberellins play some role in the changes of flowering response to chilling in the developing seedling of Pharbitis nil Choisy.