Day and night temperatures, daily light integral, and CO2 enrichment affect growth and flower development of Campanula carpatica Blue Clips
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Campanula carpatica Jacq. 'Blue Clips' plants were grown in a greenhouse under nine combinations of day and night temperatures created by moving plants every 12 h among three day/night temperatures (15, 20, and 25C). 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) created with varying supplemental light, and ambient (400 mol mol -1 ) and enriched (600 mol mol -1 ) CO 2 concentrations. Time to flower was closely related to average daily temperature (ADT), and was not significantly affected by the day or night temperatures delivered to achieve a specific ADT. Time to flower was not largely affected by DLI or CO 2 enrichment. As plant ADT increased between 15 and 25C, flower diameter decreased about 1 mm per degree and was not related to the difference between day and night temperatures (DIF). Flower diameter was smallest and least sensitive to changes in temperature at lower DLI and at ambient CO 2 levels. There were 10 less flower buds and 0.3 g less dry mass per plant at first flower for every 1 increase in plant ADT at high and medium DLIs. Flower bud number and dry mass were relatively low and less sensitive to changes in ADT at low DLI, and increased slightly with CO 2 enrichment 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 12C at all DLIs, but the response was stronger under low DLI than high and medium DLIs. Flower bud number and dry mass were correlated closely with the ratio of DLI to daily thermal time (base temperature of 0C). Flower bud number and dry mass were highest when C. carpatica plants were grown at 15C with a DLI of 10-15 mol m -2 per day. 2001 Elsevier Science B.V.
