scholarly journals Light Intensity and Light Quality from Sole-source Light-emitting Diodes Impact Phytochemical Concentrations within Brassica Microgreens

2017 ◽  
Vol 142 (1) ◽  
pp. 3-12 ◽  
Author(s):  
Joshua K. Craver ◽  
Joshua R. Gerovac ◽  
Roberto G. Lopez ◽  
Dean A. Kopsell
Keyword(s):  
Light Intensity ◽  
Light Quality ◽  
Light Emitting Diodes ◽  
Sole Source ◽  
Photon Flux ◽  
Total Phenolic ◽  
Light Emitting ◽  
Phytochemical Content ◽  
Light Intensities ◽  
Phenolic Concentration

Multilayer vertical production systems using sole-source (SS) light-emitting diodes (LEDs) can be an alternative to more traditional methods of microgreens production. One significant benefit of using LEDs is the ability to select light qualities that have beneficial impacts on plant morphology and the synthesis of health-promoting phytochemicals. Therefore, the objective of this study was to quantify the impacts of SS LEDs of different light qualities and intensities on the phytochemical content of brassica (Brassica sp.) microgreens. Specifically, phytochemical measurements included 1) total anthocyanins, 2) total and individual carotenoids, 3) total and individual chlorophylls, and 4) total phenolics. Kohlrabi (Brassica oleracea var. gongylodes), mustard (Brassica juncea ‘Garnet Giant’), and mizuna (Brassica rapa var. japonica) were grown in hydroponic tray systems placed on multilayer shelves in a walk-in growth chamber. A daily light integral (DLI) of 6, 12, or 18 mol·m−2·d−1 was achieved from SS LED arrays with light ratios (percent) of red:blue 87:13 (R87:B13), red:far-red:blue 84:7:9 (R84:FR7:B9), or red:green:blue 74:18:8 (R74:G18:B8) with a total photon flux from 400 to 800 nm of 105, 210, or 315 µmol·m−2·s–1 for 16 hours, respectively. Phytochemical measurements were collected using spectrophotometry and high-performance liquid chromatography (HPLC). Regardless of light quality, total carotenoids were significantly lower under increasing light intensities for mizuna and mustard microgreens. In addition, light quality affected total integrated chlorophyll with higher values observed under the light ratio of R87:B13 compared with R84:FR7:B9 and R74:G18:B8 for kohlrabi and mustard microgreens, respectively. For kohlrabi, with increasing light intensities, the total concentration of anthocyanins was greater compared with those grown under lower light intensities. In addition, for kohlrabi, the light ratios of R87:B13 or R84:FR7:B9 produced significantly higher anthocyanin concentrations compared with the light ratio of R74:G18:B8 under a light intensity of 315 µmol·m−2·s−1. Light quality also influenced the total phenolic concentration of kohlrabi microgreens, with significantly greater levels for the light ratio of R84:FR7:B9 compared with R74:G18:B8 under a light intensity of 105 µmol·m−2·s−1. However, the impact of light intensity on total phenolic concentration of kohlrabi was not significant. The results from this study provide further insight into the selection of light qualities and intensities using SS LEDs to achieve preferred phytochemical content of brassica microgreens.

The growth and morphology of microgreens is associated with modified ascorbate and anthocyanin profiles in response to the intensity of sole-source light-emitting diodes

2020 ◽  
Author(s):  
Chase Jones-Baumgardt ◽  
Qinglu Ying ◽  
Youbin Zheng ◽  
Gale G. Bozzo
Keyword(s):  
Light Emitting Diodes ◽  
Photosynthetic Pigment ◽  
Sole Source ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Total Phenolic ◽  
Hypocotyl Length ◽  
Total Anthocyanin ◽  
Light Emitting ◽  
Phytochemical Profiles

Sole-source light-emitting diodes (LEDs) are alternatives to fluorescent tubes and high intensity discharge lamps that are routinely used for indoor cultivation of horticultural commodities, including microgreens. This study examined the effect of photosynthetic photon flux density (PPFD) from LEDs on phytochemical profiles in organically grown kale, cabbage, arugula, and mustard microgreens, and their association with growth and morphological attributes. LEDs were used to deliver a 15% blue light and 85% red light mixture to microgreens at varying PPFDs between 100 and 600 μmol m-2 s-1. For all microgreens, increased concentrations of ascorbate (total and reduced) and total anthocyanin were proportional to PPFD. Total phenolic concentrations were elevated in all four microgreens at high PPFDs, whereas chlorophyll concentrations declined in arugula cabbage and mustard. A principal component analysis revealed anthocyanins and phenolics were associated with ascorbate levels in all microgreens, but not with chlorophylls or carotenoids. At high PPFDs photosynthetic pigment levels were negatively associated with fresh and dry weight to varying degrees. Anthocyanins, phenolics and ascorbate were negatively correlated with hypocotyl length and the colour attribute hue angle in all microgreens. These results indicate that microgreen growth and morphology are associated with altered phytochemical profiles during cultivation under sole source LEDs.

scholarly journals Light Intensity and Quality from Sole-source Light-emitting Diodes Impact Growth, Morphology, and Nutrient Content of Brassica Microgreens

HortScience ◽  
2016 ◽  
Vol 51 (5) ◽  
pp. 497-503 ◽  
Author(s):  
Joshua R. Gerovac ◽  
Joshua K. Craver ◽  
Jennifer K. Boldt ◽  
Roberto G. Lopez
Keyword(s):  
Light Emitting Diodes ◽  
Dry Weight ◽  
Nutrient Content ◽  
Sole Source ◽  
Photon Flux ◽  
Light Sources ◽  
Growth Morphology ◽  
Hypocotyl Length ◽  
Photoelectric Conversion ◽  
Light Emitting

Multilayer vertical production systems using sole-source (SS) lighting can be used for the production of microgreens; however, traditional SS lighting methods can consume large amounts of electrical energy. Light-emitting diodes (LEDs) offer many advantages over conventional light sources, including high photoelectric conversion efficiencies, narrowband spectral light quality (LQ), low thermal output, and adjustable light intensities (LIs). The objective of this study was to quantify the effects of SS LEDs of different light qualities and intensities on growth, morphology, and nutrient content of Brassica microgreens. Purple kohlrabi (Brassica oleracea L. var. gongylodes L.), mizuna (Brassica rapa L. var. japonica), and mustard [Brassica juncea (L.) Czern. ‘Garnet Giant’] were grown in hydroponic tray systems placed on multilayer shelves in a walk-in growth chamber. A daily light integral (DLI) of 6, 12, or 18 mol·m−2·d−1 was achieved from commercially available SS LED arrays with light ratios (%) of red:green:blue 74:18:8 (R74:G18:B8), red:blue 87:13 (R87:B13), or red:far-red:blue 84:7:9 (R84:FR7:B9) with a total photon flux (TPF) from 400 to 800 nm of 105, 210, or 315 µmol·m−2·s−1 for 16 hours. Regardless of LQ, as the LI increased from 105 to 315 µmol·m−2·s−1, hypocotyl length (HL) decreased and percent dry weight (DW) increased for kohlrabi, mizuna, and mustard microgreens. With increasing LI, leaf area (LA) of kohlrabi generally decreased and relative chlorophyll content (RCC) increased. In addition, nutrient content increased under low LIs regardless of LQ. The results from this study can help growers to select LIs and LQs from commercially available SS LEDs to achieve preferred growth characteristics of Brassica microgreens.

scholarly journals Growing lettuce under multispectral light-emitting diodes lamps with adjustable light intensity

2017 ◽  
Vol 11 ◽  
Author(s):  
Giacomo Tosti ◽  
Paolo Benincasa ◽  
Rossano Cortona ◽  
Beatrice Falcinelli ◽  
Michela Farneselli ◽  
...  
Keyword(s):  
Light Intensity ◽  
Conversion Efficiency ◽  
Light Emitting Diodes ◽  
Biomass Conversion ◽  
High Energy ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Emitting ◽  
Light Spectra ◽  
Use Efficiency

Light-Emitting Diodes (LEDs) technology offers vast possibilities in plant lighting due to its ability to mix different light frequencies, high energy use efficiency and low heat production combined to long lifespan. In particular, the combined effect of the Blue:Red (B:R) ratio and other frequencies in the central part of the PAR spectrum (CGA, <em>i.e.</em> cyan, green and amber) may be very important, though literature information is scarce. In this paper, the effects of six light spectra from LED technology were tested, <em>i.e.</em>: (i) B:R=0.82 (<em>i.e.</em> similar to sunlight) with CGA (treatment T0), (ii) B:R=0.82 without CGA (T1), (iii) red prevalence (B:R=0.25) without CGA (T2), (iv) blue prevalence (B:R=4) without CGA (T3), (v) red prevalence with CGA (T4) and (vi) blue prevalence with CGA (T5). The experiment was carried out in a walk-in climatic chamber with controlled temperature and relative humidity and an incident PAR photon flux density (PFD) of 300 μmol m<sup>–2</sup> s<sup>–1</sup> (14/10 light/dark photoperiod), generated by multispectral LED lamps with adjustable light intensity. Smooth leaved lettuce (Lactuca sativa L. cv Gentilina) was used as the test plant and biomass yield (DW, g m<sup>–2</sup>), LAI, soil coverage proportion (SC%), energy-biomass conversion efficiency (E-BCE, kWh g<sup>–1</sup>) and Radiation Use Efficiency (RUE, g mol<sup>–1</sup> photons) were determined. Treatments with red predominance (T2 and T4) showed the highest SC% rates, while those with blue predominance (T3 and T5) showed the lowest. Light spectrum also affected leaf size (<em>i.e. </em>mean leaf area). The highest DW and RUE were observed in T2 and T4, followed by T0, while biomass in T3 and T5 was significantly lower (similar to T1). LAI values were generally high, but treatments with blue predominance showed the lowest LAI values (both with or without CGA). The introduction of intermediate wavelengths (green, cyan and amber) did not bring about significant improvement in DW or RUE, but resulted in reduced energy-biomass conversion efficiency, mainly due to lower architectural efficiency of the CGA LEDs. Future research should clarify how to optimise the light spectra according to the crop growth phases. The adoption of spectra promoting fast growth is fundamental in the early growth, while the use of spectra maximising yield quality may be more important later on.

scholarly journals Growth Quality and Development of Olive Plants Cultured In-Vitro under Different Illumination Regimes

Plants ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2214
Author(s):  
Pablo Díaz-Rueda ◽  
Manuel Cantos-Barragán ◽  
José Manuel Colmenero-Flores
Keyword(s):  
Light Intensity ◽  
Light Quality ◽  
Woody Species ◽  
High Sensitivity ◽  
Clear Correlation ◽  
Light Emitting ◽  
Fluorescent Lamps ◽  
Light Intensities ◽  
Growth Quality

Light-emitting diodes (LEDs) are useful for the in-vitro micropropagation of plants, but little information is available on woody species. This work compares the effects of light quality and intensity on the growth and development of micropropagated olive plants from two different subspecies. Illumination was provided with fluorescent and LED lamps covering different red/blue ratios (90/10, 80/20, 70/30, 60/40) or red/blue/white combinations, as well as different light intensities (30, 34, 40, 52, 56, 84, 98 and 137 µmol m−2 s−1 of photosynthetic photon fluxes, PPF). Olive plants exhibited high sensitivity to light quality and intensity. Higher red/blue ratios or lower light intensities stimulated plant growth and biomass mainly as a consequence of a higher internodal elongation rate, not affecting either the total number of nodes or shoots. In comparison to fluorescent illumination, LED lighting improved leaf area and biomass, which additionally was positively correlated with light intensity. Stomatal frequency was positively, and pigments content negatively, correlated with light intensity, while no clear correlation was observed with light quality. In comparison with fluorescent lamps, LED illumination (particularly the 70/30 red/blue ratio with 34 µmol m−2 s−1 PPF intensity) allowed optimal manipulation and improved the quality of in-vitro micropropagated olive plants.

scholarly journals Intensity of Sole-source Light-emitting Diodes Affects Growth, Yield, and Quality of Brassicaceae Microgreens

HortScience ◽  
2019 ◽  
Vol 54 (7) ◽  
pp. 1168-1174 ◽  
Author(s):  
Chase Jones-Baumgardt ◽  
David Llewellyn ◽  
Qinglu Ying ◽  
Youbin Zheng
Keyword(s):  
Light Emitting Diodes ◽  
Flux Ratio ◽  
Growth Yield ◽  
Sole Source ◽  
Leafy Vegetables ◽  
Photon Flux ◽  
Light Emitting ◽  
Yield And Quality ◽  
Lighting Environment

Indoor farming is an increasingly popular approach for growing leafy vegetables, and under this production system, artificial light provides the sole source (SS) of radiation for photosynthesis and light signaling. With newer horticultural light-emitting diodes (LEDs), growers have the ability to manipulate the lighting environment to achieve specific production goals. However, there is limited research on LED lighting specific to microgreen production, and available research shows that there is variability in how microgreens respond to their lighting environment. The present study examined the effects of SS light intensity (LI) on growth, yield, and quality of kale (Brassica napus L. ‘Red Russian’), cabbage (Brassica oleracea L.), arugula (Eruca sativa L.), and mustard (Brassica juncea L. ‘Ruby Streaks’) microgreens grown in a walk-in growth chamber. SS LEDs were used to provide six target photosynthetic photon flux density density (PPFD) treatments: 100, 200, 300, 400, 500, and 600 μmol·m−2·s−1 with a photon flux ratio of 15 blue: 85 red and a 16-hour photoperiod. As LI increased from 100 to 600 μmol·m−2· s−1, fresh weight (FW) increased by 0.59 kg·m−2 (36%), 0.70 kg·m−2 (56%), 0.71 kg·m−2 (76%), and 0.67 kg·m−2 (82%) for kale, cabbage, arugula, and mustard, respectively. Similarly, dry weight (DW) increased by 47 g·m−2 (65%), 45 g·m−2 (69%), 64 g·m−2 (122%), and 65 g·m−2 (145%) for kale, cabbage, arugula, and mustard, respectively, as LI increased from 100 to 600 μmol·m−2· s−1. Increasing LI decreased hypocotyl length and hue angle linearly in all genotypes. Saturation of cabbage and mustard decreased linearly by 18% and 36%, respectively, as LI increased from 100 to 600 μmol·m−2·s−1. Growers can use the results of this study to optimize SS LI for their production systems, genotypes, and production goals.

scholarly journals Growth Responses of Ornamental Annual Seedlings Under Different Wavelengths of Red Light Provided by Light-emitting Diodes

HortScience ◽  
2013 ◽  
Vol 48 (12) ◽  
pp. 1478-1483 ◽  
Author(s):  
Heidi Marie Wollaeger ◽  
Erik S. Runkle
Keyword(s):  
Light Intensity ◽  
Light Emitting Diodes ◽  
Chlorophyll Concentration ◽  
Red Light ◽  
Plant Production ◽  
Photon Flux ◽  
Growth Responses ◽  
Fresh Weight ◽  
Light Emitting ◽  
Shoot Fresh Weight

Light-emitting diodes (LEDs) are of increasing interest in controlled environment plant production because of their increasing energy efficiency, long lifetime, and colors can be combined to elicit desirable plant responses. Red light (600–700 nm) is considered the most efficient wavelength for photosynthesis, but little research has compared growth responses under different wavelengths of red. We grew seedlings of impatiens (Impatiens walleriana), petunia (Petunia ×hybrida), tomato (Solanum lycopersicum), and marigold (Tagetes patula) or salvia (Salvia splendens) at 20 °C under six sole-source LED lighting treatments. In the first experiment, a photosynthetic photon flux (PPF) of 160 μmol·m−2·s–1 was provided for 18 h·d−1 by 10% blue (B; peak = 446 nm) and 10% green (G; peak = 516 nm) lights, with the remaining percentages consisting of orange (O; peak = 596 nm)–red (R; peak = 634 nm)–hyper red (HR; peak = 664 nm) of 20–30–30, 0–80–0, 0–60–20, 0–40–40, 0–20–60, and 0–0–80, respectively. There were no consistent effects of lighting treatment across species on any of the growth characteristics measured including leaf area, plant height, or shoot fresh weight. In a second experiment, seedlings were grown under two light intensities (low, 125 μmol·m−2·s–1 and high, 250 μmol·m−2·s–1) consisting of 10% B and 10% G light and the following percentages of R–HR: 0–80, 40–40, 80–0. Shoot fresh weight was similar in all light treatments, whereas shoot dry weight was often greater under the higher light intensity, especially under the 40–40 treatments. Leaf chlorophyll concentration under 40–40low, 80–0low, or both was often greater than that in plants under the high light treatments, indicating that plants acclimated to the lower light intensity to better use photons available for photosynthesis. We conclude that O, R, and HR light have generally similar effects on plant growth at the intensities tested when background G and B lights are provided and thus, selection of red LEDs for horticultural applications could be based on other factors such as economics and durability.

scholarly journals Supplemental Far-red Light-emitting Diode Light Increases Growth of Foxglove Seedlings Under Sole-source Lighting

2020 ◽  
Vol 30 (5) ◽  
pp. 564-569
Author(s):  
Claudia Elkins ◽  
Marc W. van Iersel
Keyword(s):  
Flux Density ◽  
Plant Height ◽  
Light Emitting Diode ◽  
Red Light ◽  
Dry Weight ◽  
Sole Source ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Emitting ◽  
Light Intensities

Seedlings may be grown indoors where environmental conditions can be precisely controlled to ensure consistent and reliable production. The optimal spectrum for production under sole-source lighting is currently unknown. Far-red light (λ = 700–800 nm) typically is not a significant part of the spectrum of light-emitting diode (LED) grow lights. However, far-red light is photosynthetically active and can enhance leaf elongation, which may result in larger leaves and increased light interception. We hypothesized that adding far-red light to sole-source lighting would increase the growth of ‘Dalmatian Peach’ foxglove (Digitalis purpurea) seedlings grown under white LED lights, potentially shortening production times. Our objective was to evaluate the effect of far-red light intensities, ranging from 4.0 to 68.8 µmol·m−2·s−1, on the growth and morphology of foxglove seedlings. Foxglove seedlings were grown in a growth chamber with a photosynthetic photon flux density (PPFD) of 186 ± 6.4 μmol·m−2·s−1 and supplemental far-red light intensities ranging from 4.0 to 68.8 µmol·m−2·s−1. As far-red light increased, shoot dry weight, root dry weight, plant height, and plant height/number of leaves increased by 38% (P = 0.004), 20% (P = 0.029), 38% (P = 0.025), and 34% (P = 0.024), respectively, while root weight fraction decreased 16% (P = 0.034). Although we expected supplemental far-red light to induce leaf and/or stem expansion, specific leaf area and compactness (two measures of morphology) were unaffected. Because a 37% increase in total photon flux density (PPFD plus far-red light) resulted in a 34.5% increase in total plant dry weight, the increased growth likely was due to increased photosynthesis rather than a shade-acclimation response. The growth response was linear across the 4.0 to 68.8 µmol·m−2·s−1 range of far-fed light tested, so we were unable to determine a saturating far-red photon flux density.

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