We investigated the effect of mixed radiation from light-emitting diodes (LEDs) on the growth and flowering of ageratum, marigold, and salvia bedding plants. Blue, red, and far-red lights were applied under controlled environmental conditions for 28 d. Both the combination of blue-plus-red radiation as well as fluorescent lighting treatment (control) caused increases in dry weights, but shoot lengths were shortest when plants were exposed to blue plus red light compared with either red or blue plus far-red treatments. The number of floral buds as well as the occurrence of flower opening for ageratum and salvia plants was also enhanced under the blue plus red mixture. Likewise, carbohydrate accumulation was stimulated by that combination compared with the other radiation treatments.Keywords: chlorophyll, light-emitting diodes, mixture radiation, morphogenesis, starch Environmental conditions, such as relative humidity, temperature, light intensity, and light quality, commonly influence the growth and development of plants. Among these various factors, light quality affects stem elongation, lateral branching, leaf extension and pigmentation, and photosynthetic activity (Moe and Heins, 1990;Heo et al., 2003;Jayakumar et al., 2004). Desirable morphological characteristics can be obtained when horticultural plants are grown under less light and low temperatures, thereby reducing heat energy costs with only a minimal delay in their blooming (Merritt and Kohl, 1991 ).The objectives of this study were (1) to produce ageratum, marigold, and salvia bedding plants with compact growth, good branching, and a large number of flowers when treated with different mixtures of radiation sources, and (2) to evaluate the starch and sugar contents, as well as the optimum chlorophyll fluorescence, that would cause minimal or no delays in blooming when those plants were grown under various combinations of radiation provided by lightemitting diodes (LEDs).
MATERIALS AND METHODS
Plant Materials and Growth ConditionsBedding plants of ageratum (Ageratum houstonianum Mill. cv. Blue Field), marigold (Tagetes erecta L. cv. Orange Boy), and salvia (Salvia splendens E Sello ex Ruem & Schult. cv. Red Vista) with two to four true leaves were used for our experimental materials. On Day 14 after sowing, all plants with two true leaves were transplanted to a plug tray (50 x 50 mm) filled with a soil mixture (BM1 ; Berger Horticulture, Canada) of 75 to 85% Canadian sphagnum peat moss, 15 to 20% perlite, and 4 to 10% vermiculite. Two types of liquid fertilizers, 20:10:20 and 14:0:14 (Plant Prod; Plant Products, Canada), were alternately applied at a rate of 100 ppm during the experimental period. We used an LED system (GF-320s; Good Feeling, Korea) comprising LED sticks, a panel, and a main controller to maintain a photosynthetic *Corresponding author; fax +82-43-272-5369 e-mail paekky@chungbuk.ac.kr photon flux (PPF) of 90 _+ 10 ~mol m -2 5 -1 over a 16-h photoperiod, as measured on an empty culture shelf. All plants were reared for 28 d in a growth c...