Temperature and daily light integral influence plant quality and flower development of Campanula carpatica 'Blue Clips' and 'Deep Blue Clips', and Campanula 'Birch Hybrid'

The effects of temperature on flower size and number of flower buds of Camp anula carpatica Jacq. 'Blue Clips', 'Deep Blue Clips', and Campanula 'Birch Hybrid' were investigated in four temperature and light-transfer experimen ts. In year 1, 'Blue Clips' and 'Birch Hybrid' plants were grown initially at 20 degreesC and then transferred at visible flower bud (VB) to 14, 17, 2 0, 23, or 26 degreesC until flower (Expt. 1). In Expt. 2, 'Blue Clips' and 'Birch Hybrid' plants were transferred from 14 to 26 degreesC or from 26 to 14 degreesC at various intervals after flower induction. Flower size of bo th species was negatively correlated with average daily temperature (ADT) a fter VB; flowers on plants grown at 14 degreesC were 35% larger than those on plants grown at 26 OC. In contrast, temperature before VB had only a sma ll effect on final flower size in both species, although flower diameter of 'Birch Hybrid' plants grown at constant 26 degreesC was 20 % smaller than that of the plants grown initially at 20 degreesC and then transferred to V B to 26 degreesC. For both species, the longer the exposure to high tempera ture after VB, the smaller the flowers. Number of flower buds at flower in 'Birch Hybrid' decreased as ADT after VB increased. In year 2, 'Deep Blue C lips' plants were grown at constant 20 degreesC under high or low daily lig ht integral (DLI, 17 or 5.7 mol.m-2.d(-1)) until VB, and then transferred t o 14, 17, 20, 23, or 26 degreesC under high or low DLI (Expt. 3). In Expt. 4, 'Deep Blue Clips' plants were grown at 14, 17, 20, 23, or 26 degreesC un til VB, and then transferred to constant 20 degreesC under high or low DLI until flower. Flower size (petal length) was negatively correlated with ADT both before and after VB, while flower bud number was negatively correlate d with the ADT only after VB, regardless of DLI. In both experiments, petal length decreased by 0.3 to 0.5 mm per 1 degreesC increase in ADT before or after VB. Flowers were larger and more numerous under high than under low DLIs after VB, regardless of the DLI before VB.