Quantum Flux Density Studies of Chrysanthemum in a Controlled Environment with High-pressure Sodium Lamps. II. Long Day and Short Day Studies1

Abstract

Abstract Growth of chrysanthemum (Chrysanthemum morifolium Ramat) was studied as a function of quantum flux density (QFD), QFD duration, and temperature. Plants were grown under high-pressure sodium (HPS) lamps in a controlled environment (CE) for 13 long days and during the first 2 weeks of short days. Treated plants were also grown to flowering in a greenhouse to determine treatment effect on flowering time and plant size at flowering. Dry weight of vegetative shoots was greatest at 27°C after cuttings were rooted. Rooting and growing chrysanthemum cuttings vegetatively in a CE under HPS lamps appeared best at 280 μEm−2s−1 for 18 hours/day when plants were grown to flowering in a greenhouse. Flower initiation was not accelerated at QFD greater than 140 μEm−2s−1 provided 12 hours/day. A photochlorosis was observed on all treatments irradiated with HPS lamps; the photochlorosis was irreparable at QFD of 420 μEm−2s−1.