Day and night temperatures, daily light integral, and CO2 enrichment affect growth and flower development of Campanula carpatica 'Blue Clips'

Campanula carpatica Jacq. 'Blue Clips' plants were grown in a greenhouse un der nine combinations of day and night temperatures created by moving plant s every 12 h among three day/night temperatures (15, 20, and 25 degreesC). At each temperature, there were three daily light integrals (DLI; 4.2, 10.8 , and 15.8 mol m(-2) per day, averaged over the experimental period) create d with varying supplemental light, and ambient (approximate to 400 mu mol m ol(-1)) and enriched (approximate to 600 mu mol mol(-1)) CO:! concentration s. Time to flower was closely related to average daily temperature (ADT), a nd was not significantly affected by the day or night temperatures delivere d to achieve a specific ADT. Time to flower was not largely affected by DLI or CO2 enrichment. As plant ADT increased between 15 and 25 degreesC, flow er diameter decreased about 1 mm per degree and was not related to the diff erence between day and night temperatures (DIF). Flower diameter was smalle st and least sensitive to changes in temperature at lower DLI and at ambien t CO2 levels. There were 10 less flower buds and 0.3 g less dry mass per pl ant at first flower for every 1 degrees increase in plant ADT at high and m edium DLIs. Flower bud number and dry mass were relatively low and less sen sitive to changes in ADT at low DLI, and increased slightly with CO2 enrich ment at medium and high but not at low DLI. Plant height was not related to ADT, but increased linearly as DIF increased from -6 to 12 degreesC at all DLIs, but the response was stronger under low DLI than high and medium DLI s. Flower bud number and dry mass were correlated closely with the ratio of DLI to daily thermal time (base temperature of 0 degreesC). Flower bud num ber and dry mass were highest when C. carpatica plants were grown at 15 deg reesC with a DLI of 10-15 mol m(-2) per day. (C) 2001 Elsevier Science B.V. All rights reserved.