TEMPERATURE AFFECTS GROWTH AND FLOWERING OF THE BALLOON FLOWER [PLATYCODON GRANDIFLORUS (JACQ.) A.DC.CV.ASTRA BLUE]

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