EFFECTS OF DAY-NIGHT TEMPERATURE-VARIATIONS ON GROWTH, MORPHOGENESIS AND FLOWERING OF KALANCHOE-BLOSSFELDIANA V POELLN AT DIFFERENT CO2 CONCENTRATIONS, DAYLENGTHS AND PHOTON FLUX DENSITIES

Growth and flowering of Kalanchoe blossfeldiana were studied at two te mperature treatments (constant, CT; day lower than night temperature, negative DIF) in combination with two CO2 concentrations (360 and 900 mu mol mol(-1)), two daylengths (DL; 12 and 18 h) and two photosynthet ic photon flux densities (PPFD; 85 and 130 mu mol m(-2) s(-1)). In add ition to the two temperature treatments, a 2-h low temperature pulse ( DROP) was included in combination with short days and low CO2 levels. The experiment was conducted in 18 growth chambers with artificial lig ht only. The plant dry weight at saleable stage was the same at the di fferent temperature treatments irrespective of CO2 concentration, DL o r PPFD. The dry weight was similarly (31-40%) increased by CO2 enrichm ent, or increasing DL or PPFD. Total plant height was slightly, but co nsistently increased by negative DIF relative to CT, irrespective of t he level of the other climate factors. The DROP treatment in short DL increased the height relative to both negative DIF and CT. Negative DI F delayed flowering by 2-4 days at 360 mu mol mol(-1) CO2, but promote d it by 2-4 days at 900 mu mol mol(-1) CO2. Fresh weight of flowers wa s unaffected by temperatun treatments irrespective of DL and PPFD. It was concluded that the best plant quality was obtained at constant tem perature throughout day and night irrespective of the level of the oth er climate factors.