Effect of LED spectra on growth, physiology, and biochemical profiles of African marigold (Tagetes erecta L.)

The effects of the light-emitting diode (LED) spectra on plant growth, flowering, and phytochemical accumulation of African marigold were assessed under controlled conditions. The combination of white, blue, and red LEDs prolonged the time to flower by up to 20 d compared to full white LEDs and other light treatments. The white LEDs are an insufficient lighting condition for marigold growth, indicated by the lower plant and flower biomass. The dichromatic blue-red light and the white-blue-red (WBR) light were most suitable for marigold growth, biomass production, as well as flower quantity and quality. In addition, the highest contents of flavonoids and phenolics were observed in leaves and petals of marigold plants under the WBR treatment. Importantly, the extended spectrum of LEDs, achieved by supplementing white LEDs with the blue-red LEDs, could provide a friendly visual environment for researchers and workers under closed environments and plant factories.