Effect of Pre-Harvest Supplemental UV-A/Blue and Red/Blue LED Lighting on Lettuce Growth and Nutritional Quality

Hooks, Triston; Masabni, Joseph; Sun, Ling; Niu, Genhua

doi:10.3390/horticulturae7040080

Cited by 12 publications

(9 citation statements)

References 43 publications

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“…For instance, lettuce 'Cherokee' grown in a greenhouse had increased leaf redness when 100 mmol•m À2 •s À1 of EOP R, B or R1B light was added for at least the last 3 d of production (up to 14 d) (Owen and Lopez 2015). Furthermore, 171 mmol•m À2 •s À1 of supplemental lighting that included low-wavelength B (peak 5 403 nm) or R1B light in a greenhouse increased shoot fresh and dry mass, leaf area, TPC, TAC, and carotenoid concentration of lettuce 'Red Mist', but the magnitude depended on the daily light integral, duration of lighting (2 or 4 d), and whether it was applied at night or during the day (Hooks et al 2021). In another study, anthocyanin content, but not phenolic content, of lettuce 'Codex' and 'Rouxai' increased 2-fold when high-intensity EOP light with a high percentage of B light (69% B 1 31% R) was applied for the last 4 d of production (G omez and Jim enez 2020).…”

Section: Discussionmentioning

confidence: 97%

“…A moderate to high PFD of B light typically suppresses plant growth and leaf expansion (Cosgrove 1981;Ohashi-Kaneko et al 2007;Shin et al 2014;Son and Oh 2015), but the effects of UVA on plant growth are less clear and vary among species (Verdaguer et al 2017). Some studies indicate that UVA can promote plant growth and leaf expansion (Chen et al 2019;Hooks et al 2021), whereas others report inhibitory effects, similar to B light (Krizek et al 1998;Tsormpatsidis et al 2008). In the present study, EOP lighting treatments did not increase shoot fresh mass (Fig.…”

Section: Discussionmentioning

confidence: 99%

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End-of-production Ultraviolet A and Blue Light Similarly Increase Lettuce Coloration and Phytochemical Concentrations

Kelly

Runkle

2023

horts

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Anthocyanins are a group of human-health-promoting phenolic compounds that influence the pigmentation of red-leaf lettuce (Lactuca sativa). Ultraviolet A (UVA; 315–399 nm) and blue (B; 400–499 nm) light can increase the concentrations of phenolic compounds but also suppress cellular expansion, which can limit harvestable biomass accumulation. It is not known whether UVA or B light is more effective at increasing phenolic compound concentrations when they are each applied at the same photon flux density. Our objective was to evaluate the efficacy of UVA and B light when added during the end of production (EOP) at promoting phenolic compound synthesis and red-leaf coloration without limiting biomass accumulation. We grew red-leaf lettuce ‘Rouxai’ in a controlled indoor environment at an air temperature of 22 °C under warm-white and red light-emitting diodes (LEDs). On day 24, 30 or 60 µmol·m−2·s−1 from UVA, B, UVA plus B, or red plus green LEDs was added during the last 6 days of the 30-day production period. UVA and B light, alone or combined, similarly increased leaf redness (by up to 72%), total phenolic concentration (by up to 92%), total anthocyanin concentration (by up to 2.7-fold), and relative chlorophyll concentration (by up to 20%) and did not inhibit growth, compared with lettuce grown without EOP supplemental lighting. Considering B light was as effective as UVA light at increasing leaf color and phytonutrient density and that B LEDs are more electrically effective, economical, and durable, an enriched blue-light spectrum at the EOP is a comparatively sustainable method to increase crop quality without suppressing biomass accumulation.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

End-of-production Ultraviolet A and Blue Light Similarly Increase Lettuce Coloration and Phytochemical Concentrations

Kelly

Runkle

2023

horts

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“…In addition, adding UVA (5-7% of photosynthetic photon flux density) to blue-LEDs reduced plant height for some microgreen species [14]. Our recent study found that short-term preharvest lighting treatment with UVA/Blue LEDs (containing both UVA and blue wavelengths) increased the antioxidant concentrations of greenhouse-grown lettuce plants without compromising plant growth and biomass [15,16]. To the best of our knowledge, the effects of adding UVA to W-LEDs on the growth and quality of indoor microgreens, for either the whole production period or at the end, remain unknown.…”

Section: Introductionmentioning

confidence: 94%

Adding UVA and Far-Red Light to White LED Affects Growth, Morphology, and Phytochemicals of Indoor-Grown Microgreens

Hooks¹,

Sun²,

Kong³

et al. 2022

Sustainability

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White light emitting diodes (LED) have commonly been used as a sole light source for the indoor production of microgreens. However, the response of microgreens to the inclusion of ultraviolet A (UVA) and/or far-red (FR) light to white LED light remains unknown. To investigate the effects of adding UVA and FR light to white LEDs on plant biomass, height, and the concentrations of phytochemicals, four species of microgreens including basil, cabbage, kale, and kohlrabi were grown under six light treatments. The first three treatments were white LED (control) and two UVA treatments (adding UVA to white LED for the whole growth period or for the last 5 days). Another three treatments consisted of adding FR to the first three treatments. The total photon flux density (TPFD) for all six light treatments was the same. The percentages of UVA and FR photons in the TPFD were 23% and 32%, respectively. Compared to white LEDs, adding UVA throughout the growth period did not affect plant height in all the species except for basil, where 9% reduction was observed regardless of the FR light. On the contrary, the addition of FR light increased plant heights by 9–18% for basil, cabbage, and kohlrabi, regardless of the UVA treatment, compared to white LED. Furthermore, regardless of UVA, adding FR to white LEDs reduced the plant biomass, total phenolic contents, and antioxidant concentrations for at least one species. There was no interaction between FR and UVA on all the above growth and quality traits for all the species. In summary, microgreens were more sensitive to the addition of FR light compared to UVA; however, the addition of FR to white LEDs may reduce yields and phytochemicals in some species.

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“…According to Zha et al (2020), ascorbate tends to be present at higher levels in lettuce cultivated under LEDs supplying 75% blue and 25% red light relative to those delivering 25% blue and 75% red, and 50% blue and 50% red light. Pre-harvest supplemental lighting using UV-A and blue or red/blue LED lighting can increase the growth and nutritional quality of lettuce grown hydroponically (Brazaitytė et al, 2015;Verdaguer et al, 2017;Hooks et al, 2021). We can conclude that, by manipulating the colour of the lamps used, we can better support and direct the yield, growth, and nutrition of plants.…”

Section: Influence Of Environmental Conditions On the Quantity And Quality Of Microgreen Production In Hydroponic Systemmentioning

confidence: 99%

Influence of environmental and nutritional factors on the development of lettuce (Lactuca sativa L.) microgreens grown in a hydroponic system: A review

Rusu

Moraru

Mintaș

2021

Not Bot Horti Agrobo

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Lettuce microgreens are one of the most popular vegetables due to them being perceived as a “healthy food”, with high concentrations of nutrients, beneficial vitamins, and minerals. With a short vegetation period, they can be cultivated with minimum investment, and they are increasingly accepted by consumers, as they are healthy and easy to prepare. Lettuce has high ecological plasticity, but, despite this, its phenotypic expression, morphology, physiology, and anatomy are significantly influenced by environmental conditions. Lettuce microgreens contain higher quantities of phytonutrients and minerals and lower quantities of nitrates at the early stage of development than at the completely developed stage. The environmental conditions that influence the development of lettuce microgreens (and their quality) in a hydroponic system are as follows (average ideal values): light (400 W), photoperiodicity (12 h), light intensity (400 µmol m−2 s−1), colour spectrum (440-460 nm), temperature (20 ± 2 °C), and humidity (80 ± 5 %). The nutritional solution in a hydroponic system must be carefully monitored, by checking certain essential parameters such as the following (average ideal values): pH (6.3 ± 0.4), electrical conductivity (1.8 ± 0.2 mS), dissolved oxygen (6 mg L−1), and temperature (18 ± 2 °C). The analysis of expert literature reveals that there is a need to establish certain protocols for cultivating microgreens in hydroponic systems, to minimize the factors that can negatively influence the plants, in order to obtain higher concentrations of active substances.

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Effect of Pre-Harvest Supplemental UV-A/Blue and Red/Blue LED Lighting on Lettuce Growth and Nutritional Quality

Cited by 12 publications

References 43 publications

End-of-production Ultraviolet A and Blue Light Similarly Increase Lettuce Coloration and Phytochemical Concentrations

End-of-production Ultraviolet A and Blue Light Similarly Increase Lettuce Coloration and Phytochemical Concentrations

Adding UVA and Far-Red Light to White LED Affects Growth, Morphology, and Phytochemicals of Indoor-Grown Microgreens

Influence of environmental and nutritional factors on the development of lettuce (Lactuca sativa L.) microgreens grown in a hydroponic system: A review

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