Effects of Daily Light Integral and LED Spectrum on Growth and Nutritional Quality of Hydroponic Spinach

To achieve clean and high-quality spinach production, the effects of daily light integral (DLI) and light spectrum on growth, nutritional quality, and energy yield of hydroponic spinach (Spinacia oleracea L.) were investigated in a closed plant factory under light-emitting diode (LED) lighting. The hydroponic spinach plants were grown under 16 combinations of four levels of DLI (11.5, 14.4, 17.3, and 20.2 mol m−2 day−1) with four light spectra: LED lamps with ratio of red light to blue light (R:B ratio) of 0.9, 1.2, and 2.2 and fluorescent lamps with R:B ratio of 1.8 as control. The results show that total fresh and dry weights, energy yield, and light energy use efficiency (LUE) of harvested spinach were higher under D17.3-L1.2 treatment compared to other treatments. The higher net photosynthetic rates were shown at DLI of 17.3 mol m−2 day−1 regardless of light quality. Higher vitamin C contents of spinach in all LED treatments were obtained compared with the control. L1.2 treatments with higher fraction of blue light led to more vitamin C content, lower nitrate content, and higher LUE independent of DLI. L2.2 treatment with more fraction of red light was beneficial to reduce oxalate accumulation. Power consumption based on increased total fresh weight under LED lamps with R:B ratio of 1.2 in different DLIs was over 38% lower than that under the fluorescent lamps and 1.73 kWh per 100 g FW at DLI of 17.3 mol m−2 day−1. In conclusion, lighting environment in DLI of 17.3 mol m−2 day−1 using LED lamps with R:B ratio of 1.2 is suggested for the design of a LED plant factory for hydroponic spinach production.

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

Horticulturae ◽

10.3390/horticulturae7040080 ◽

2021 ◽

Vol 7 (4) ◽

pp. 80

Author(s):

Triston Hooks ◽

Joseph Masabni ◽

Ling Sun ◽

Genhua Niu

Keyword(s):

Blue Light ◽

Nutritional Quality ◽

Uv Light ◽

Ultra Violet ◽

Photon Flux ◽

Photon Flux Density ◽

Daily Light Integral ◽

Lettuce Growth ◽

Supplemental Lighting

Blue light and ultra-violet (UV) light have been shown to influence plant growth, morphology, and quality. In this study, we investigated the effects of pre-harvest supplemental lighting using UV-A and blue (UV-A/Blue) light and red and blue (RB) light on growth and nutritional quality of lettuce grown hydroponically in two greenhouse experiments. The RB spectrum was applied pre-harvest for two days or nights, while the UV-A/Blue spectrum was applied pre-harvest for two or four days or nights. All pre-harvest supplemental lighting treatments had a same duration of 12 h with a photon flux density (PFD) of 171 μmol m−2 s−1. Results of both experiments showed that pre-harvest supplemental lighting using UV A/Blue or RB light can increase the growth and nutritional quality of lettuce grown hydroponically. The enhancement of lettuce growth and nutritional quality by the pre-harvest supplemental lighting was more effective under low daily light integral (DLI) compared to a high DLI and tended to be more effective when applied during the night, regardless of spectrum.

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Improvement of the Growth and Nutritional Quality of Two-leaf-color Pak Choi by Supplemental Alternating Red and Blue Light

HortScience ◽

10.21273/hortsci15180-20 ◽

2020 ◽

pp. 1-8

Author(s):

Jing Huang ◽

Ya-liang Xu ◽

Fa-min Duan ◽

Xu Du ◽

Qi-chang Yang ◽

...

Keyword(s):

Phenolic Compounds ◽

Vitamin C ◽

Blue Light ◽

Nutritional Quality ◽

Green Leaf ◽

Carotenoid Content ◽

Leaf Color ◽

Time Intervals ◽

Pak Choi

The aim of the present study was to evaluate the effects of alternating red (660 nm) and blue (460 nm) light on the growth and nutritional quality of two-leaf-color pak choi (Brassica campestris L. ssp. chinensis var. communis). Four light treatments (supplemental alternating red and blue light with intervals of 0, 1, 2, and 4 hours, with a monochromatic light intensity of 100 μmol·m−2·s−1 and a cumulative lighting time of 16 hours per day) were conducted in a greenhouse under identical ambient light conditions (90 to 120 μmol·m−2·s−1 at 12:00 am) for 10 days before green- and red-leaf pak choi were harvested. The results showed that the two-leaf-color pak choi receiving alternating red and blue light exhibited more compact canopies and wider leaves than those under the control treatment, which was attributed to the shade avoidance syndrome of plants. The present study indicated that the biomass of green-leaf pak choi was much higher than that of red-leaf pak choi, but the nutritional quality of green-leaf pak choi was lower than that of red-leaf pak choi, and seemingly indicating that the regulation of metabolism for pak choi was species specific under light exposure. The trends of both biomass and the soluble sugar content were highest under the 1-hour treatment. The contents of chlorophyll a and total chlorophyll in both cultivars (green- and red-leaf pak choi) were significantly increased compared with control, without significant differences among the 1-, 2-, and 4-hour treatments, whereas chlorophyll b exhibited no significant difference in any treatment. Alternating red- and blue-light treatment significantly affected the carotenoid content, but different trends in green- and red-leaf pak choi were observed, with the highest contents being detected under the 1-hour and 4-hour treatments, respectively. With increasing time intervals, the highest soluble protein contents in two-leaf-color pak choi were observed in the 4-hour treatment, whereas nitrate contents were significantly decreased in the 4-hour treatment. Compared with 0 hours, the contents of vitamin C, phenolic compounds, flavonoids, and anthocyanins in two-leaf-color pak choi were significantly increased, but no significant differences were observed in vitamin C, phenolic compounds, and flavonoids among the 1-, 2-, and 4-hour treatments, similar to what was found for the anthocyanin content of green-leaf pak choi. However, the content of anthocyanins in red-leaf pak choi gradually increased with increasing time intervals, with the highest content being found in the 4-hour treatment. Supplemental alternating red and blue light slightly increased the antioxidant capacity [1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rate and antioxidant power], but no significant differences were observed after 1, 2, and 4 hours of treatment. Taken together, treatment with an interval of 1 hour was the most effective for increasing the biomass of pak choi in this study, but treatment with a 4-hour interval should be considered to enhance the accumulation of health-promoting compounds.

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The Comparison of Constant and Dynamic Red and Blue Light Irradiation Effects on Red and Green Leaf Lettuce

Agronomy ◽

10.3390/agronomy10111802 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1802

Author(s):

Akvilė Viršilė ◽

Jurga Miliauskienė ◽

Perttu Juhani Haimi ◽

Kristina Laužikė ◽

Giedrė Samuolienė

Keyword(s):

Blue Light ◽

Green Leaf ◽

Remarkable Effect ◽

Constant Flux ◽

Natural Lighting ◽

Daily Light Integral ◽

Lighting Intensity ◽

Leaf Lettuce ◽

Dynamic Lighting ◽

Light Integral

In this study, we sought to evaluate and compare the effects of constant and dynamic lighting on red and green leaf lettuce (Lactuca sativa L. Red Cos and Lobjoits Green cos) cultivated in a controlled environment. Plants were illuminated with the combination of red 662 and 638 nm, blue 452 nm, and far-red 737 nm at 16 h photoperiod and constant daily light integral (DLI) of each component. Five constant or dynamic lighting treatments were performed: (BR) constant flux of both B452 and R662; (B*R) constant flux of R662, but the DLI of B452 condensed in 8 h in the middle of photoperiod doubling the PPFD of blue light; (BR*) constant flux of B452, but the DLI of R662 light condensed in the middle of photoperiod; (BdynR) constant flux of R662, but the flux of B452 varies in the sinusoidal profile during 16 h photoperiod, imitating diurnal increase and decrease in lighting intensity; and (BRdyn) constant flux of B452, but the flux of R662 varies in sinusoidal profile. The lettuce’s response to dynamic lighting strategies was cultivar specific. Dynamic lighting strategies, mimicking natural lighting fluctuations, did not have a remarkable effect on photosynthesis and antioxidative parameters, but the dynamic flux of blue light component had a pronounced effect on higher macro and microelement contents in lettuce leaves.

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Growth and Bioactive Compound Synthesis in Cultivated Lettuce Subject to Light-quality Changes

HortScience ◽

10.21273/hortsci11592-16 ◽

2017 ◽

Vol 52 (4) ◽

pp. 584-591 ◽

Cited By ~ 8

Author(s):

Ki-Ho Son ◽

Jin-Hui Lee ◽

Youngjae Oh ◽

Daeil Kim ◽

Myung-Min Oh ◽

...

Keyword(s):

Blue Light ◽

Bioactive Compounds ◽

Light Quality ◽

Red Light ◽

Monochromatic Light ◽

Bioactive Compound ◽

Light Emitting ◽

Compound Synthesis ◽

Plant Factory ◽

Ferulic Acids

This study aimed to determine the effect of changes in light quality on the improvement of growth and bioactive compound synthesis in red-leaf lettuce (Lactuca sativa L. ‘Sunmang’) grown in a plant factory with electrical lighting. Lettuce seedlings were subjected to 12 light treatments combining five lighting sources: red (R; 655 nm), blue (B; 456 nm), and different ratios of red and blue light combined with three light-emitting diodes [LEDs (R9B1, R8B2, and R6B4)]. Treatments were divided into control (continuous irradiation of each light source for 4 weeks), monochromatic (changing from R to B at 1, 2, or 3 weeks after the onset of the experiments), and combined (changing from R9B1 to R8B2 or R6B4 at 2 or 3 weeks after the onset of the experiments). Growth and photosynthetic rates of lettuce increased with increasing ratios of red light, whereas chlorophyll and antioxidant phenolic content decreased with increasing ratios of red light. Individual phenolic compounds, including chlorogenic, caffeic, chicoric, and ferulic acids, and kaempferol, showed a similar trend to that of total phenolics. Moreover, transcript levels of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) genes were rapidly upregulated by changing light quality from red to blue. Although the concentration of bioactive compounds in lettuce leaves enhanced with blue light, their contents per lettuce plant were more directly affected by red light, suggesting that biomass as well as bioactive compounds’ accumulation should be considered to enhance phytochemical production. In addition, results suggested that growth and antioxidant phenolic compound synthesis were more sensitive to monochromatic light than to combined light variations. In conclusion, the adjustment of light quality at a specific growth stage should be considered as a strategic tool for improving crop yield, nutritional quality, or both in a plant factory with electrical lighting.

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Development of Lettuce Plant in Spring and Autumn Period, Effects of Led Lightening on the Quantity of Mineral Substrates and Leaf Nitrate

Asian Journal of Soil Science and Plant Nutrition ◽

10.9734/ajsspn/2019/v5i330065 ◽

2019 ◽

pp. 1-9

Author(s):

Seda Bice Ataklı ◽

Sezer Şahin

Keyword(s):

Blue Light ◽

Red Light ◽

Early Spring ◽

Nutrient Concentrations ◽

Nitrate Content ◽

Winter Period ◽

Significant Difference ◽

Spring And Autumn Period ◽

Leaf Nitrate ◽

Curly Leaf

Aims: This study was performed during early spring and winter period of 2015-2016 by utilizing soilles technique in a non-heated glasshouse that belongs to Gaziosmanpaşa University Faculty of Agriculture. Study Design: Whereas Funly F1 lettuce species was used as vegetal materials, 2:1 ratio cocopeat and perlite mixture was used as cultivation environment. According to the experiment design, experiment coincidence parcels were performed as 3-recurrences. In the experiment, the effects of different colored LED lights (blue, yellow, red, blue + yellow, blue + red, yellow + red, blue + yellow + red) additional to sunlight were examined. Results: SMD strip LEDs with different colors were used as light source. The light practice does not affect on the plant diameter, plant lenght, SÇKM, pH, titered acid, vitamin C and plant nutrient concentrations. Statistically significant difference occured in the yield of spring and winter curly leaf head salad. There was also an increase at 1% importance level in the light practices compared to the control. In the experiment, red and red blue light combinations had an increase of 1% in the curly leaf head salads in the yield rate when it was compared to the control. Whereas the highest total plant head weight was 840 gr/piece in spring practice, and it was 732 gr/piece for the red light practices in winter practice. Compared to the control, the amount of plant leaf nitrate for the light practices resulted in a decrease at 1% importance level in the curly leaf head salad. When the results were compared with the control conditions, the lowest nitrate contents were obtained as 1764.5 mg NO3-kg- in spring practices, 1898.6 NO3-kg- in winter practices. Coclusion: More amount of nitrate was observed on the leaves of curly leaf head salad in winter practice compared to the one in spring. The amount of leaf nitrate decreased in the light practices compared to the control. As a result, the red and blue light practices and their combinations improved the amount of yield and plant growth by reducing nitrate content.

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Continuous Irradiation with Alternating Red and Blue Light Enhances Plant Growth While Keeping Nutritional Quality in Lettuce

HortScience ◽

10.21273/hortsci13469-18 ◽

2018 ◽

Vol 53 (12) ◽

pp. 1804-1809 ◽

Cited By ~ 6

Author(s):

Noriko Ohtake ◽

Masaharu Ishikura ◽

Hiroshi Suzuki ◽

Wataru Yamori ◽

Eiji Goto

Keyword(s):

Plant Growth ◽

Leaf Area ◽

Blue Light ◽

Nutritional Quality ◽

Continuous Irradiation ◽

Light Emitting ◽

Artificial Lighting ◽

Fluorescent Lamps ◽

High Concentrations ◽

Net Assimilation

Plant factories with artificial lighting have been developed to improve food production, functional ingredients, and profitability. Intensive research has been performed to elucidate the effects of light intensity and wavelength on plant growth and nutritional quality with the use of light-emitting diodes (LEDs). In particular, the effects of monochromatic red, blue, or simultaneous red + blue light have been studied because these wavelengths are predominantly used for photosynthesis. We examined the effects of alternating red and blue light provided by LEDs over a period of 24 hours on the growth and nutritional properties of leafy lettuce. The results clearly show that alternating red and blue light accelerated plant growth significantly compared with white fluorescent lamps or red and blue LEDs at the same daily light integral. Plants grown under alternating red/blue light had a greater net assimilation rate and total and projected leaf area (an indicator of the fraction of leaf area that absorbs more light) than other plants. Additionally, alternating red and blue light maintained high concentrations of sugars, ascorbic acid, and anthocyanins in leaves. Taken together, the results indicate that continuous irradiation with alternating red and blue light could enhance growth while maintaining the nutritional quality in lettuce.

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Effects of Light Wavelength on Daughter Cladode Growth and Quality in Edible Cactus Nopalea cochenillifera Cultured in a Plant Factory with Artificial Light

Journal of Horticultural Research ◽

10.2478/johr-2018-0018 ◽

2018 ◽

Vol 26 (2) ◽

pp. 71-80

Author(s):

Takanori Horibe ◽

Shousei Imai ◽

Takuya Matsuoka

Keyword(s):

Blue Light ◽

Radical Scavenging Activity ◽

Single Mother ◽

Red Light ◽

Radical Scavenging ◽

Light Wavelength ◽

Simultaneous Irradiation ◽

Plant Factory ◽

Nopalea Cochenillifera

AbstractIn this study, we investigated the effects of different-colored light-emitting diodes (LEDs) on the growth and quality of daughter cladodes of the edible cactus Nopalea cochenillifera. Cladodes were cultured hydroponically using the deep-flow technique under red, blue, or a combination of red and blue, or red, blue, and green light in an enclosed-type plant factory. We found that daughter cladodes developed from the mother cladodes in all the treatments, despite pH of the nutrient solution drastically decreasing over time. However, the elongation growth rate of the first daughter cladodes and the number of daughter cladodes produced were highest under red light and lowest under blue light, indicating that blue light suppresses daughter cladode development. The total fresh weight (FW) of the daughter cladodes emerging from a single mother cladode was also lowest under blue light. However, the average FW of the daughter cladodes was the highest under blue light, or under simultaneous irradiation with red and blue light. The number of spines, which is an undesirable characteristic in edible cacti, was significantly lower under red light than under blue light, while the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of the daughter cladodes was the highest under blue light or under simultaneous irradiation with red and blue light. Our results show that light wavelength has a strong effect on daughter cladode development in N. cochenillifera, so controlling the light environment represents an effective approach for improving the growth and quality of this edible cactus.

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Improving Spinach, Radish, and Lettuce Growth under Red Light-emitting Diodes (LEDs) with Blue Light Supplementation

HortScience ◽

10.21273/hortsci.36.2.380 ◽

2001 ◽

Vol 36 (2) ◽

pp. 380-383 ◽

Cited By ~ 186

Author(s):

Neil C. Yorio ◽

Gregory D. Goins ◽

Hollie R. Kagie ◽

Raymond M. Wheeler ◽

John C. Sager

Keyword(s):

Blue Light ◽

Light Emitting Diodes ◽

Red Light ◽

Dry Weight ◽

Photon Flux ◽

Light Emitting ◽

Fluorescent Lamps ◽

Spinacea Oleracea ◽

Total Dry Weight ◽

Red Leds

Radish (Raphanus sativus L. cv. Cherriette), lettuce (Lactuca sativa L. cv. Waldmann's Green), and spinach (Spinacea oleracea L. cv. Nordic IV) plants were grown under 660-nm red light-emitting diodes (LEDs) and were compared at equal photosynthetic photon flux (PPF) with either plants grown under cool-white fluorescent lamps (CWF) or red LEDs supplemented with 10% (30 μmol·m-2·s-1) blue light (400-500 nm) from blue fluorescent (BF) lamps. At 21 days after planting (DAP), leaf photosynthetic rates and stomatal conductance were greater for plants grown under CWF light than for those grown under red LEDs, with or without supplemental blue light. At harvest (21 DAP), total dry-weight accumulation was significantly lower for all species tested when grown under red LEDs alone than when grown under CWF light or red LEDs + 10% BF light. Moreover, total dry weight for radish and spinach was significantly lower under red LEDs + 10% BF than under CWF light, suggesting that addition of blue light to the red LEDs was still insufficient for achieving maximal growth for these crops.

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Phototropin 1 and dim-blue light modulate the red light de-etiolation response

Plant Signaling & Behavior ◽

10.4161/15592324.2014.976158 ◽

2014 ◽

Vol 9 (11) ◽

pp. e976158

Author(s):

Yihai Wang ◽

Kevin M Folta

Keyword(s):

Blue Light ◽

Red Light

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Single Wavelengths of LED Light Supplement Promote the Biosynthesis of Major Cyclic Monoterpenes in Japanese Mint

Plants ◽

10.3390/plants10071420 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1420

Author(s):

Takahiro Ueda ◽

Miki Murata ◽

Ken Yokawa

Keyword(s):

Blue Light ◽

Solid Phase ◽

Glandular Trichomes ◽

Red Light ◽

Glandular Trichome ◽

Pulse Amplitude ◽

Light Treatment ◽

Led Light ◽

Trichome Formation ◽

Japanese Mint

Environmental light conditions influence the biosynthesis of monoterpenes in the mint plant. Cyclic terpenes, such as menthol, menthone, pulegone, and menthofuran, are major odor components synthesized in mint leaves. However, it is unclear how light for cultivation affects the contents of these compounds. Artificial lighting using light-emitting diodes (LEDs) for plant cultivation has the advantage of preferential wavelength control. Here, we monitored monoterpene contents in hydroponically cultivated Japanese mint leaves under blue, red, or far-red wavelengths of LED light supplements. Volatile cyclic monoterpenes, pulegone, menthone, menthol, and menthofuran were quantified using the head-space solid phase microextraction method. As a result, all light wavelengths promoted the biosynthesis of the compounds. Remarkably, two weeks of blue-light supplement increased all compounds: pulegone (362% increase compared to the control), menthofuran (285%), menthone (223%), and menthol (389%). Red light slightly promoted pulegone (256%), menthofuran (178%), and menthol (197%). Interestingly, the accumulation of menthone (229%) or menthofuran (339%) was observed with far-red light treatment. The quantification of glandular trichomes density revealed that no increase under light supplement was confirmed. Blue light treatment even suppressed the glandular trichome formation. No promotion of photosynthesis was observed by pulse-amplitude-modulation (PAM) fluorometry. The present result indicates that light supplements directly promoted the biosynthetic pathways of cyclic monoterpenes.

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