## 3 Results and Discussion
### Effects of LEDs on Phenylpropanol Content in Wheat Sprouts  
After treatment with white, blue, or red light for 4, 8, or 12 days, the content of phenylpropanoids was analyzed in wheat sprouts by HPLC analysis (Figure 4). Our results indicate that different lights exerted different effects on phenylpropanol biosynthesis. The accumulation of phenylpropanoids, except that of epicatechin, was gradually increased at 4 to 12 days of growth under all light conditions. Epicatechin, one of the main phenylpropanoids found in wheat sprouting. The highest content of epicatechin was observed at 4 days and gradually decreased at 8 to 12 days under all three LEDs lights condition. The highest content of epicatechin (616.56 \(\mathrm{\SIUnitSymbolMicro g}\)/g dry weight) was found at 4 days of growth under white light; this was 1.46- fold and 1.3-fold higher than that observed under blue or red light, respectively. The high content of epicatechin observed under white light coincided with the expression of _TaDFR_, which decreased at 4 to 12 days of growth. Figure 3: Expression levels of genes involved in phenylpropanol biosynthesis in wheat sprouts irradiated with white, blue, or red LED light. The means and standard deviations were obtained from three independent experiments. Letters a–g indicates significant differences (\(p<0.05\)). In this study, six soluble phenolic compounds (gallic acid, p-coumaric acid, ferulic acid, 4-hydroxybenzoic acid, quercetin, and epicatchin) were detected in wheat sprouts exposed to different types of LEDs. Our results agree with those of previous studies reporting the presence of 4-hydroxybenzoic acid [32], ferulic acid [32], p-coumaric acid [32], gallic acid [33], and epicatchin [33] in wheat sprouts. Under all the light conditions used in this study, the contents of gallic acid, 4-hydroxybenzoic acid, p-coumaric acid, and quercetin were gradually increased and reached a maximum at 12 days; this coincided with the expression of _TaPAL2_, _TaC4H_, _Ta4 CL1_, _TaCHS_, and _TaF3H_, which was increased at 4 to 12 days. The accumulation of ferulic acid peaked at 8 DAS, decreased under blue and red light, but gradually increased under white light. Under blue light, the accumulation of gallic acid (20.18 \(\upmu\)g/g dry weight) at 8 days of growth was 1.2-fold and 1.5-fold higher  
Figure 4: Phenylpropanolic content (\(\upmu\)g/g dry weight) in wheat sprouts irradiated with white, blue, and red LED lights. Samples were harvested after 4, 8, and 12 days of growth under illumination and used for HPLC analysis. The means and standard deviations were obtained from three independent experiments. Letters a–e indicate significant differences (\(p<0.05\)). than that observed under white and red light, respectively, and this accumulation maintains for up to 12 days. The content of quercetin in wheat sprouts was increased at 4 to 12 days under all the LED light conditions used in this study. However, under blue light, the accumulation of quercetin was the highest at 12 days (51.77 ug/g dry weight), which was 3.12-fold and 1.9-fold higher than that observed under white and red light, respectively. The effect of blue light on the accumulation of secondary compounds in plants has been examined previously. In Norway spruce, blue light enhances the accumulation of flavonoids, lignin, and phenylpropanoids [34]. Blue light also promotes the accumulation of polyphenols in lettuce [6] and that of phenolic compounds in Chinese cabbage [13]. In this study, treatment with red light affected the content of p-coumaric acid in wheat sprouts. The accumulation of p-coumaric acid was the highest (8.11 ug/g dry weight) at 12 days of growth under red light, which was 1.27-fold and 1.77-fold higher than that observed under white and blue light, respectively. This coincided with the expression of _TaPAL3_ and _TaPAL4_, which was highest under red light. Red light also has been reported to enhance the accumulation of charantin in bitter melon [12], aliphatic glucosinolates in kale [2], and \(\beta\)-cryptoxanthin in citrus fruit [35].