LED illumination affects bioactive compounds in romaine baby leaf lettuce

Abstract

BACKGROUND The effect of light quality on phytochemicals in romaine baby leaf lettuce ‘Thumper’ was investigated in (I) a closed environment and (II, III) a greenhouse (16 h, 21/17 °C): (I) basal (638, 455, 660, 735 nm) LEDs supplemented with UV (380 nm), green (510 nm), yellow (595 nm) or orange (622 nm) LEDs (PPFD of ∼175 µmol m−2 s−1); (II) high‐pressure sodium (HPS) lamps (90 µmol m−2 s−1) supplemented with blue (455, 470nm) or green (505, 530nm) LEDs (30 µmol m−2 s−1); (III) at 3 days before harvesting, HPS lamps (90 µmol m−2 s−1) supplemented with red (638 nm) LEDs (210 µmol m−2 s−1). RESULTS (I) Supplemental UV or orange light enhanced phenolic compounds, supplemental UV or green light enhanced α‐carotene, and supplemental green light enhanced anthocyanins. All supplemental LED colours had a negative effect on tocopherol and ascorbic acid levels. (II) HPS lighting supplemented with different LEDs was not efficient, since the increase in some compounds did not compensate the decrease in major tested phytochemicals. (III) Short‐term irradiation with supplemental 638 nm LEDs before harvesting in the greenhouse did not have a significant effect on phytochemical contents, apart from enhancing tocopherols. CONCLUSION Wavelength control using LED technology affects the production of secondary metabolites, as the metabolism of many nutrients is light‐dependent. The narrow‐bandwidth supplemental light effects were diminished by broader‐spectrum HPS light or natural daylight in the greenhouse. © 2013 Society of Chemical Industry

Influence of Yellow Light-Emitting Diodes at 590 nm on Storage of Apple, Tomato and Bell Pepper Fruit

“…A previous investigation reported higher AAC in tomato fruit when blue light (450 nm) was applied (19 Similarly, there was higher AOP in all of the LED light-irradiated samples; indeed, the diff erences in AOP were statistically signifi cant compared to the controls for apple peel and red bell pepper fruit (13). In the previously mentioned study on romaine baby leaf lett uce during the growth period signifi cantly higher AOP was also reported when supplemental green light (530 nm) was used, compared to yellow light in the present study (590 nm).…”

“…Gangadhar et al (44) reported that blue LED light enhanced the synthesis of chlorophyll a and chlorophyll b in chilli pepper fruit, while the combination of red and blue LED light resulted in the highest carotenoid levels. Samuolienė et al (13) also reported a decrease in tocopherol content in the romaine baby leaf lett uce under LED light conditions. The colour readings for the apple, tomato and red bell pepper fruit samples are summarised in Table 3.…”

“…In comparison with the data of the present study, other studies have shown slightly lower TPC values (but higher TFC; see also below) in the fruit of several pepper cultivars (40). Samuolienė et al (13) again reported that supplemental orange light (622 nm) enhanced the synthesis of phenolic compounds in romaine baby leaf lett uce during the growth period. They also reported in another study (21) that supplemental LED light at 505 nm promoted signifi cant increases in TPC, but on the other hand, LED light at 535 nm resulted in signifi cantly lower TPC.…”

“…Irradiation in visible and UV range can induce stress that evokes antioxidant defence system responses (13).…”

Prospects for Using Environmental Levers in Greenhouses to Stimulate Plant Defences and the Quality of Fruits and Vegetables

“…For instance, red light increased concentrations of anthocyanins in tomato fruit (Mancinelli, 1985), whereas blue light increased concentrations of carotenoids (Gautier et al, 2005). Even green light, long believed to play no role in plants, has recently been reported to increase the concentration in anthocyanins in lettuce (Samuoliené et al, 2013). Ultraviolet (UV) radiations also have been observed to stimulate the synthesis of secondary metabolites (Jansen et al, 2008) and can be exploited to stimulate natural defences against diseases such as grey mould (Charles et al, 2008(Charles et al, , 2009).…”