Temperature affects growth and flowering of the balloon flower [Platycodon grandiflorus (jacq.) A. Dc. cv. Astra blue]

Abstract

The effects of temperature from 14 to 29 °C on the growth and flowering of Platycodon grandiflorus (Jacq.) A. DC. cv. Astra Blue are described. Under greenhouse conditions, seedlings flowered earliest (after 45 days) when grown at 29 °C, vs. after 108 days when grown at 14 °C. Height at flowering was greatest at 19 °C and branch number was greatest (13 per plant) at 22 °C. Fresh and dry mass and leaf area at flowering increased with decreasing temperature. Imbibing seeds at 4 °C prior to germination had no significant affect on the time to flowering or the number of nodes below the flower. In a growth chamber experiment, apical dissections showed that flowers were initiated earlier at 20 °C than at 10 °C. These results show that the balloon flower is highly sensitive to temperature, but cool temperatures delay the time to flower initiation or flowering.