Cultivation of crops under supplemental light treatments This study was carried out during August to September, 2010 at Andong National University glasshouse, Andong, Korea Republic. Amaranth (cultivar: red amaranth, Bangladesh) and buckwheat seeds were sown densely on different plastic trays each contained a commercial soil mixture (moisture 70%, WHC 30-50%, pH 5.5 -7.0, EC 1.3 dsm-1, NH4N 300 mg/L, NO3N 400 mg/L, P2O5 500 mg/L, CEC 30-100 c molt kg-1). The trays were kept in a growth chamber maintained at 30°C and 50% RH for germination of the seeds. After ten days, the trays were shifted to a glasshouse under supplemental light treatments. The glasshouse was maintained at 30±5°C and 70±10% RH. The LED light sources were placed horizontally 25 cm above the plant canopy. Each LED panel consisted of 20 LED sticks with a main controller (LPRS Series, Good Feeling Co. Ltd., Korea). The experiment was conducted with five light treatments: red (R) 660 nm, blue (B) 470 nm, far red (FR) 740 nm, blue + red light (BR), (B: R =1:1 in energy ratio), and control observation was made without supplemental light following the photoperiod from 5.00 to 21.00 h. Under each light source two trays were subjected for 15 days and therefore, vegetative growth and phytochemic al characteristics of the plants were measured.
Observation of plant characteristics The stem length, 2nd inter node length, leaf length, leaf width were measured using slide caliper. Number of node and number of leaf were counted and plant fresh weights were measured using an electric balance (GF-200, Korea).
Determination of ascorbic acid A modified protocol reported by Gahler et al. (2003) was used for determination of ascorbic acid. 10 g fresh plant sample for each treatment was mixed separately with 40 mL of 5% meta phosphoric acid and blended using a blender (AG-2000, Korea). The mixtures were shaken at 250 rpm for 5 minutes and then centrifuged at 3,000xg for 10 minutes. The supernatant among the mixtures were used for determination of the concentration of ascorbic acid using HPLC equipped with C18 column (Agilent Tech. 1200 Series). The absorbance of each eluant was measured at 254 nm and concentrations were determined against ascorbic acid standards and expressed as mg/g FW.
Total phenolic compounds The method described by Singleton and Rossi (1965) was used to determine total phenolic compounds. 50 mg freeze-dried plant samples for each treatment was separately mixed with 10 mL 80% methanol and shaken at 240 rpm for 16 h. After filtering, 50 µL of the solution was taken in a test tube and then 350 µL H2O was added to it. Therefore, 200 pL 2N Folin-Ciocalteu reagents (Sigma Chemical Co.) were poured into the test tube. The mixture was incubated for 1 h at 25°C prior to mixing 1.0 mL 10% Na2CO3. Absorbance of the mixture was measured at 735 nm using UV 5000 VIS NIR spectrophotometer (Varian Tech., Australia) with a standard curve to estimate gallic acid (Sigma Chemical Co.) equivalent concentrations. Total phenolic compound was expressed as mg of gallic acid equivalents per gram (mg GAE/ g DW) of dry weight sample.
Anthocyanin Anthocyanin was estimated according to the extraction protocol of Revilla et al. (1998). 30 mg freeze-dried sample for each treatment was separately mixed with 5 mL 2% HC1 in methanol for 36 h. The liquid extract was separated by centrifugation (VS-15CFN) at 1446xg for 15 minutes. For each sample, 400 pL aliquots were diluted to 2.0 mL with potassium chloride (0.025 M, pH 1.0) and sodium acetate (0.4 M, pH 4.5) buffer solutions. After 15 minutes, both the solutions were filtered (0.2 um pore size) and then absorbance was measured at 515 nm. Maximum absorption was confirmed in separate scans taken with a UV-5000 VIS NIR spectrophotometer (Varian Tech., Australia) and 700 nm for haze correction. Total anthocyanin concentrations were expressed as cyaniding-3-glucoside equivalent values.
Total chlorophyll A total of 100 mg fresh leaf tissue was dissolved in 5 mL N, N dimethylformamide and kept overnight. The absorbance of extract solution was measured at 647 nm and 664 nm using UV-5000 VIS MR spectrophotometer (Varian Tech., Australia). Chlorophyll concentration was calculated using the following equation (Moran 1982). Total chlorophyll (µg/m1) = 7.04 A664+20.27 A647. Data Analysis Data were analyzed by analysis of variance (ANOVA) and the mean values were separated by Duncan's Multiple Range Test (DMRT) using PASW Statistics 18 (SPSS Inc., Chicago, Illinois, USA).