|Authors: ||H. Yoshida, K. Sekiguchi, L. Okushima, S. Sase, N. Fukuda|
|Keywords: ||antioxidant, blue light, CO2 enrichment, polyphenol, LED, red light|
Chlorogenic acid (CGA) has been attracting attention as an antioxidant that affects human health.
As we previously reported, overnight supplemental lighting (OSL) with light-emitting diodes (LEDs) can promote the growth of some leafy vegetables.
However, when we investigated some functional materials in lettuce 'Greenwave' grown under OSL, a drastic increase in CGA concentration was observed.
In Experiment 1, plants were exposed to low and high intensities (10 and 50 Ámol m-2 s-1, respectively) of OSL using blue, green, red, and far-red LEDs in growth chambers equipped with white fluorescent lamps as the main light source.
In the growth chamber, we set the photoperiod such that the day/night time was 10/14 h.
OSL was used for irradiation for 14 h during the night.
OSL with blue and red LEDs increased the CGA concentration compared with that obtained using no supplemental lighting; however, other light qualities of OSL could not demonstrate any change in the CGA concentration.
In particular, five times higher CGA concentration (60 mg 100 g FW-1) was observed in lettuce grown under OSL using red LEDs with high intensity than those grown under no supplemental lighting.
In Experiment 2, lettuce plants were grown under OSL (17:00-7:00 HR) with red LEDs in a greenhouse throughout the year.
Unlike the results of experiment 1, the CGA concentration in lettuce was unstable, and OSL could not maintain a high CGA concentration, particularly during summer.
However, during winter, OSL increased the CGA concentration in lettuce.
Furthermore, CO2 enrichment under OSL increased the CGA concentration up to 50 mg 100 g FW-1 on day 14 of treatment in the greenhouse.
Therefore, it was concluded that OSL and CO2 enrichment can promote CGA accumulation in lettuce; however, the increased CGA concentration under OSL could depend on other environmental factors.
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