OPTIMIZATION OF LIGHTING SPECTRUM FOR PHOTOSYNTHETIC SYSTEM AND PRODUCTIVITY OF LETTUCE BY USING LIGHT-EMITTING DIODES (original) (raw)
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Journal of the Faculty of Agriculture, Kyushu University
This study discussed the influence of light-emitting diodes (LEDs) with red, blue, green, and yellow light on the growth and photosynthetic efficiency of Boston lettuce and Ziyan lettuce as a reference for lettuce production in plant factories. The experiments were conducted in a plant factory under a 120 µmole・m-2 ・s-1 photosynthetic photon flux density, CO 2 concentration of 1000 ppm, and daytime and nighttime temperature of 25°C/18 h and 17°C/6 h, respectively. The experiment results revealed that after 15 days of treatment under different spectral qualities, the appearances of the two lettuce leaves differed slightly. The fresh and dry weights of the Boston lettuce were highest under green light treatment. The fresh and dry weights of the Ziyan lettuce were higher under red and green light, and blue light helped the leaves to change color. In addition, photosynthesis analyzers were used to investigate the photosynthetic efficiency of the two types of lettuce under the four spectral qualities under the six luminous intensity levels of 20, 40, 60, 80, 100, and 120 µmole・m-2 ・s-1 and six CO 2 concentrations of 400, 600, 800, 1000, 1200, and 1400 ppm. The photosynthetic efficiency of the two types of lettuce generally increased with increasing luminous intensity and CO 2 concentration. When the luminous intensity was 100 and 120 µmole・m-2 ・s-1 and the CO 2 concentration was 1200 ppm and 1400 ppm, the Boston lettuce had the highest photosynthetic efficiency under green light. When luminous intensity was 120 µmole・m-2 ・s-1 and the CO 2 concentration was over 1000 ppm, the Ziyan lettuce had the highest photosynthetic efficiency under red light. These results revealed that the monochromatic LED light most suitable for growth differed across types of lettuce. In this experiment, the yield and photosynthetic efficiency of Boston lettuce were highest under green light. Those of Ziyan lettuce were highest under red light.
Horticulturae, 2022
Plant factories using artificial light to produce vegetables have high energy costs due to the high demand for electricity for lighting. Compared to conventional light sources, light-emitting diodes (LEDs) offer the possibility of tailoring the light spectrum and regulating light intensity and are more energy-efficient in terms of energy conversion regardless of the levels of lighting intensity. Optimal light intensity and daily light integral (DLI) requirements are key factors for plant growth; however, their values vary among species and varieties. Our experiment aimed to identify the best light intensity to produce lettuce plants in controlled environment. Lettuce plants of the type Batavia cv ‘Blackhawk’ were grown in plastic pots filled with perlite and peat (20:80 v/v) for 33 days in a growth chamber under blue (B, 20%) and red (R, 80%) LED light at a photosynthetic flux density of 130 µmol m−2 s−1 (BR 130, DLI 7.49 mol m−2 d−1), 259 µmol m−2 s−1 (BR 259, DLI 14.92 mol m−2 d−1...
Agriculture, 2020
Plant production in urban areas is receiving much attention due to its potential role in feeding the rapidly growing population of city dwellers. However, higher energy demands in urban plant factories are among the key challenges that need to be addressed. Artificial lighting is responsible for the most significant levels of energy consumption in plant factories; therefore, lighting systems must be modulated in consideration of the sustainable food-energy nexus. In this context, low light irradiation using blue (B) and red (R) LED was applied in a plant factory for the growth of red leaf lettuce (Lactuca sativa L. var Lollo rosso) to evaluate the growth performance and functional quality. The tested B (450 nm) and R (660 nm) light ratios were B/R = 5:1; 3:1; 1:1; 1:3, and 1:5, with a photosynthetic photon flux density (PPFD) of 90 ± 3 µmol m −2 s −1. In the plant factory, the photoperiod, temperature, RH, and CO 2 conditions were 16 h d −1 , 20 ± 0.5 • C, 65% ± 5%, and 360 ± 10 µL L −1 , respectively. The lettuce was harvested 10 and 20 days after the commencement of LED light treatment (DAT). In this study, normal photosynthetic activity and good visual quality of the lettuce were observed. The results show that a higher fraction of R (B/R = 1:5) significantly increased plant growth parameters such as plant height, leaf area, specific leaf area, plant fresh and dry weight, and carbohydrate content. By contrast, a higher fraction of B (B/R = 5:1) significantly increased the photosynthetic parameters and contents of pigment and phenolic compounds. The rate of photosynthetic performance, carbohydrates (except starch), and content of phenolic compounds were highest after 10 DAT, whereas the pigment contents did not significantly differ at the different growth stages. It is concluded that high R fractions favor plant growth and carbohydrate content, while high B fractions favor photosynthetic performance and the accumulation of pigments and phenolic compounds in red leaf lettuce under limited lighting conditions. This study will help in designing artificial lighting conditions for plant factory production to reduce energy demands.
Plants
This study focused on the physiology, growth and antioxidant activity response of hydroponically grown lettuce (Lactuca sativa L.) under sole-source LED lighting of differing spectra. Lighting spectra were provided by differing combinations of LEDs of three different peak wavelengths, (Blue 435, Blue 450, and Red 663 nm) with ratios of B450/R663: 1.25 ± 0.1, B450/R663: 1.25 ± 0.1, and B450/R663 1:1 at two light intensities of photosynthetically active radiation (PAR) (270 μmol m−2 s−1 and 60 μmol m−2 s−1). A further experiment was conducted, in which Blue and Red LEDs were supplemented with Green (Blue 450, Red 663, and Green 520 nm) with ratios of B435/R663: 1.25 ± 0.1, B450/R663/G520: 1/0.73/0.26, and B450/R663: 1.25 ± 0.1. LED light intensities under the different spectra were adjusted to deliver the same level of PAR (270 ± 20 μmol m−2 s−1). Results from the first experiment showed that increased fraction of blue 435 nm in combination with red light at 663 nm at high irradiance ...
Scientia Horticulturae, 2020
Light drives photosynthesis and regulates plant morphology, physiology, and phytochemical content. Using light emitting diodes (LEDs), customized spectra can be created, including spectrum that simulates solar light. The aim of this study was to assess the growth, development, and phytochemical content at three marketable stages of lettuce (transplant, baby-leaf, and head-lettuce) under a sun-simulated spectrum and common light spectra used in indoor growing systems. Oakleaf red (Salanova® 'Red Oakleaf') and green (Salanova® 'Green Oakleaf') lettuce were grown under seven spectra. A sun-simulated light treatment (SUN) was created with 5 % ultraviolet-A (UV-A), 20 % blue (B), 26 % green (G), 26 % red (R), and 23 % far-red (FR) light as percent photon flux density (PFD). In addition, five treatments of differing blue:red (B:R) ratios were evaluated: 0B:100R (100R), 20B:80R, 50B:50R, 80B:20R, and 100B:0R (100B) and fluorescent white light was used as a control (6500 K). Plants were provided with 200 ± 0.7 μmol•m −2 •s −1 biologically active radiation (300-800 nm) for 18 h and grown at 20.0 ± 0.2°C temperature. Fresh mass of lettuce in the SUN treatment was not significantly different when compared to B:R light treatments in all harvest dates despite the 36 % greater photosynthetic photon flux density (PPFD) in B:R treatments. Plant dry mass on day 17 of' Green Oakleaf' and 'Red Oakleaf' grown under 20B:80R was 15-39 % greater than those grown in 100B and SUN. When calculating total dry mass accumulation to cumulative yield photon flux density (YPFD), plants in SUN treatment accumulated the same dry mass per YPFD input (mg mol −1). Leaf area at day 42 of plants in 100B, SUN, and FL was 39-78 % greater than plants in B:R treatments. At final harvest (day 42), plant stem length in SUN was 2.1-4.4 times longer than in all other treatments, indicating bolting and flowering initiation. Both total phenolic and anthocyanin concentrations were greater in the B:R treatments than in SUN, 100R, and 100B treatments. This study presents baseline information for lettuce responses under LED-simulated SUN spectrum when compared to common B:R treatments and offers insights on lettuce growth and morphology under different spectra at multiple growth stages.
Scientific Reports
LED lighting in indoor farming systems allows to modulate the spectrum to fit plant needs. Red (R) and blue (B) lights are often used, being highly active for photosynthesis. The effect of R and B spectral components on lettuce plant physiology and biochemistry and resource use efficiency were studied. Five red:blue (RB) ratios (0.5-1-2-3-4) supplied by LED and a fluorescent control (RB = 1) were tested in six experiments in controlled conditions (PPFD = 215 μmol m −2 s −1 , daylength 16 h). LED lighting increased yield (1.6 folds) and energy use efficiency (2.8 folds) as compared with fluorescent lamps. Adoption of RB = 3 maximised yield (by 2 folds as compared with RB = 0.5), also increasing leaf chlorophyll and flavonoids concentrations and the uptake of nitrogen, phosphorus, potassium and magnesium. As the red portion of the spectrum increased, photosystem II quantum efficiency decreased but transpiration decreased more rapidly, resulting in increased water use efficiency up to RB = 3 (75 g fW L −1 H 2 O). The transpiration decrease was accompanied by lower stomatal conductance, which was associated to lower stomatal density, despite an increased stomatal size. Both energy and land surface use efficiency were highest at RB ≥ 3. We hereby suggest a RB ratio of 3 for sustainable indoor lettuce cultivation.
Scientia Horticulturae, 2016
In this study, effects of alternating red light (R) and blue light (B) provided by LEDs on the growth and nutritional properties of 'Green Oak leaf' lettuce were examined. Four alternating light treatments (R/B) had the same 8.64 μmol m −2 daily light integral (DLI) and similar R:B ratio (2:1), but different R/B alternating intervals that were respectively 8 h, 4 h, 2 h, and 1 h during a 16 h photoperiod. Two simultaneous light treatments, one of which (RB) had the same DLI and energy consumption with the alternating light treatments, while the other (RB') had the same photoperiod with the alternating light treatments were set up to compare the concurrently and alternately provided R and B. Results showed that different types of radiation led to obvious morphological changes, plants with simultaneous RB appeared the most sparse while those with RB' looked the most compact. Plant height/width and leaf length/width were all the highest under R/B (8 h) followed by R/B (1 h). Lettuce biomass under RB' was significantly higher than others, more than twice that under RB, R/B (4 h) and R/B (2 h), but less than twice that under R/B (8 h) and R/B (1 h). RB' significantly decreased the soluble sugar content by 9%-32% while increased crude fiber content by 14%-39% compared with others. Significantly higher ascorbic acid content as well as lower nitrate content were detected in lettuce under R/B (4 h) and R/B (2 h), while significantly lower ascorbic acid content as well as higher nitrate content were detected in lettuce under R/B (8 h) and R/B (1 h). In all, based on the same energy consumption, R/B (8 h) and R/B (1 h) resulted in higher yield, while R/B (4 h) and R/B (2 h) brought about higher nutritive value compared with the cocurrent light RB. Therefore, we conclude that lettuce growth and qualities can be purposely adjusted by adopting different alternating intervals of red and blue light. Meanwhile, the alternating modes will provide methods for deeply studying the relationship of red and blue light when acting on plants.
Effects of LED light spectra on lettuce growth and nutritional composition
Lighting Research & Technology, 2017
Year-round greenhouse production in northern latitudes depends on the use of artificial lighting. Light emitting diodes provide a promising means to save energy during cultivation as well as to modify the light spectrum to regulate the growth and quality of the crop. We compared the effects of light emitting diode lighting with different spectral compositions on the growth, development and nutritional quality of lettuce ( Lactuca sativa L. ‘Frillice’). We show that warm-white and warm-white supplemented with blue spectra provide equal growth and product quality compared to conventional high-pressure sodium lighting in the absence and presence of daylight. Our data indicate that for biomass accumulation, the far-red component in the light spectrum is more critical than green light or the red/blue ratio. Furthermore, we demonstrate that a red + blue spectrum increases the concentration of several vitamins in lettuce. However, biomass accumulation using this spectrum was insufficient w...
Plants, 2022
The optimization of plant-specific LED lighting protocols for indoor plant growing systems needs both basic and applied research. Experiments with lettuce, Lactuca sativa L., plants using artificial lighting based on narrow-band LEDs were carried out in a controlled environment. We investigated plant responses to the exclusion of certain spectral ranges of light in the region of photosynthetically active radiation (PAR); in comparison, the responses to quasimonochromatic radiation in the red and blue regions were studied separately. The data on plant phenotyping, photosynthetic activity determination, and PAM fluorometry, indicating plant functional activity and stress responses to anomalous light environments, are presented. The study on carbon isotopic composition of photoassimilates in the diel cycle made it possible to characterize the balance of carboxylation and photorespiration processes in the leaves, using a previously developed oscillatory model of photosynthesis. Thus, th...