Growth, nutritional quality, and energy use efficiency in two lettuce cultivars as influenced by white plus red versus red plus blue LEDs

Abstract

Red plus blue light-emitting diodes (LEDs) are commonly applied in plant factories with artificial lighting due to photosynthetic pigments, which absorb strongly in red and blue light regions of the spectrum. However, plants grown under natural environment are used to utilizing broad-wide spectrum by long-term evolution. In order to examine the effects of addition light added in red plus blue LEDs or white LEDs, green and purple leaf lettuces (Lactuca sativa L. cv. Lvdie and Ziya) were hydroponically cultivated for 20 days under white LEDs, white plus red LEDs, red plus blue LEDs, and red plus blue LEDs supplemented with ultraviolet, green or far-red light, respectively. The results indicated that the addition of far-red light in red plus blue LEDs increased leaf fresh and dry weights of green leaf lettuce by 28% and 34%, respectively. Addition of ultraviolet light did not induce any differences in growth and energy use efficiency in both lettuce cultivars, while supplementing green light with red plus blue LEDs reduced the vitamin C content of green leaf lettuce by 44% and anthocyanin content of purple leaf lettuce by 30% compared with red plus blue LEDs, respectively. Spectral absorbencies of purple leaf lettuce grown under red plus blue LEDs supplemented with green light were lower in green light region compared with those grown under red plus blue LEDs, which was associated with anthocyanin contents. White plus red LEDs significantly increased leaf fresh and dry weights of purple leaf lettuce by 25%, and no significant differences were observed in vitamin C and nitrate contents compared with white LEDs. Fresh weight, light and electrical energy use efficiencies of hydroponic green and purple leaf lettuces grown under white plus red LEDs were higher or no significant differences compared with those grown under red plus blue LEDs. In conclusion, white plus red LEDs were suggested to substitute for red plus blue LEDs in hydroponic lettuce (cv. Lvdie and Ziya) production in plant factories with artificial lighting.

Light-emitting diode spectra modify nutritional status, physiological response, and secondary metabolites in Ficus hirta and Alpinia oxyphylla

“…Empirical data reveals that red-light benefits carbon dioxide (CO2) assimilation rate, while green-and blue-lights impair CO2 assimilation in low and moderate to high light conditions, respectively (Landi et al, 2020). A large number of studies have tested the effects of different light wavelengths on morphological growth, dry mass accumulation, gas exchange, and photosynthesis ( Kang et al, 2016;Claypool and Lieth, 2020;Yan et al, 2020). Results from these studies have limited application meaning unless they were tested in a widebandwidth spectrum (Landi et al, 2020).…”

Challenges and Opportunities of Light-Emitting Diode (LED) as Key to Modulate Antioxidant Compounds in Plants. A Review

“…In purple leaf lettuce ( Lactuca sativa L. cv. Ziya) grown under WL plus RL, no significant differences were observed in Vit C content compared with WL [ 76 ]. In lettuce plants under continuous light for 12 days, the ratio 25RL/75BL increased the Vit C level mainly by promoting Vit C regeneration rather than its biosynthesis.…”

Changes in biochemical properties of tomato (cv.240) affected by combination of blue/red optical spectra and Calfomyth spray (Ca and P)

“…According to the report of Ajdanian et al [26] , the more the percentage of the blue light, the more the amount of chlorophyll was considerably increased based on 1% LSD. The highest amount of chlorophyll a, b and total was observed under 60R:40B treatment with values of 9.4, 5.68, and 15.09 mg/g FW leaf, respectively [26] , but no remarkable differences were observed in chlorophyll contents of two lettuce cultivars grown under red plus blue LEDs and white plus red LEDs in some research [37] .…”