Effect of different light emitting diode (LED) light quality parameters on the maturation period and development of flowers in hot pepper (Capsicum annuum L.)

The need for a lengthy maturation period is a key factor that reduces the market value of hot peppers (Capsicum annuum L.). A study was performed to assess the effects of the red (R)/blue (B)/white (W) qualities of light at reducing the period of maturation and changes in the metabolites of hot peppers. The use of the 4R:1B:5W group produced the optimal parameter of light qualities, which resulted in a higher percentage of red fruits, earlier seed development and a shorter maturation period. Additional research showed that the reduction in the period of maturation is closely related to the stage from seed to flowering owing to observation of the need for more days to complete the stage in all the groups. A combined analysis of the transcriptome-metabolome in the hot pepper flowers showed that the purple flowers in the 4R:1B:5W group were associated with an increase in the contents of flavonoids, particularly vitexin and cyanin, which are regulated by various metabolites, such as p-coumaroyl quinic acid, taxifolin, and quercetin among others. Increased levels of the total organic acids and phenolics, as shown by the decrease in the contents of total amino acids and carbohydrates also play a key role in the development of flowers in the 4R:1B:5W group. This may be closely related to the plant hormones induced by the quality of light. Ethylene responsive factors, particularly ERF021, were identified as potential hub regulators during the development of flowers owing to their involvement in all the associated metabolic pathways. This finding will provide key insights to improve the commercial value of hot peppers.