Effects of day/night temperature variations on growth, morphogenesis and flowering of Kalanchoe blossfeldiana v. Poelln. at different CO 2 concentrations, daylengths and photon flux densities

Abstract

Growth and flowering of Kalanchoe blossfeldiana were studied at two temperature treatments (constant, CT; day lower than night temperature, negative DIF) in combination with two CO 2 concentrations (360 and 900 μmol mol −1), two daylengths (DL; 12 and 18 h) and two photosynthetic photon flux densities (PPFD; 85 and 130 μmol m −2 s −1). In addition to the two temperature treatments, a 2-h low temperature pulse (DROP) was included in combination with short days and low CO 2 levels. The experiment was conducted in 18 growth chambers with artificial light only. The plant dry weight at saleable stage was the same at the different temperature treatments irrespective of CO 2 concentration, DL or PPFD. The dry weight was similarly (31–40%) increased by CO 2 enrichment, or increasing DL or PPFD. Total plant height was slightly, but consistently increased by negative DIF relative to CT, irrespective of the level of the other climate factors. The DROP treatment in short DL increased the height relative to both negative DIF and CT. Negative DIF delayed flowering by 2–4 days at 360 μmol mol −1 CO 2, but promoted it by 2–4 days at 900 μmol mol −1 CO 2. Fresh weight of flowers was unaffected by temperature treatments irrespective of DL and PPFD. It was concluded that the best plant quality was obtained at constant temperature throughout day and night irrespective of the level of the other climate factors.