Day and night temperatures, daily light integral, and CO2 enrichment affect growth and flower development of pansy (Viola xwittrockiana)

Pansy [Viola xwittrockiana Gams,'Delta Yellow Blotch' (Yellow) and 'Delta P rimrose Blotch' (Primrose)] plants were grown in a greenhouse under two CO2 concentrations [ambient (approximate to 400 mu mol.mol(-1)) and enriched ( approximate to 600 mu mol.mol(-1))], three daily light integrals (DLI; 4.1, 10.6, and 15.6 mol.m(-2).d(-1)), and nine combinations of day and night te mperatures created by moving plants every 12 h among three temperatures (15 , 20, and 25 degrees C). Time to flower decreased and rate of flower develo pment increased as plant average daily temperature (ADT) increased at all D LIs for Yellow or at high and medium DLIs for Primrose. Increasing the DLI from 4.1 to 10.6 mol.m(-2).d(-1) also decreased time to flower by 4 and 12 days for Yellow and Primrose, respectively. Both cultivars' flower size and Yellow's dry weight [(DW); shoot, flower bud, and total] decreased linearl y as plant ADT increased at high and medium DLIs, regardless of how tempera ture was delivered during day and night. DW in Yellow increased 50% to 100% when DLI increased from 4.1 to 10.6 mol.m(-2).d(-1) under both CO2 concent rations. Flower size in Yellow and Primrose increased 25% under both CO2 co nditions as DLI increased from 4.1 to 10.6 mol.m(-2).d(-1), but there was n o increase between 10.6 and 15.6 mol.m(-2).d(-1), regardless of CO2 concent ration. Plant height and flower peduncle length in Yellow increased linearl y as the difference between day and night temperatures (DIF) increased; the increase was larger under lower than higher DLIs, The ratio of leaf length to width (LL/LW) and petiole length in Yellow increased as on increased at medium and low DLIs. Carbon dioxide enrichment increased flower size by 4% to 10% and DW by 10% to 30% except for that of the shoot at medium DLI, bu t did not affect flower developmental rate or morphology. DW of vegetative and reproductive parts of the plant was correlated closely with phototherma l ratio, a parameter that describes the combined effect of temperature and light.