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Lighting is a fundamental driver of plant productivity in controlled-environment agriculture (CEA), directly affecting physiological processes, resource efficiency, and sustainability. This study evaluates the effects of distinct lighting systems, industrial Light-Emitting Diodes (iLEDs), horticultural LEDs (hLEDs), high-pressure sodium (HPS) lamps, and controls (no supplemental light), each providing unique light spectra, on cucumber (Cucumis sativus L.) growth, physiology, and environmental impact under a controlled light intensity of 250 µmol m−2 s−1 in a commercial CEA setup. The results indicated that iLEDs enhance intrinsic water use efficiency (35.65 µmol CO2/mol H2O) and reduce transpiration, reflecting superior physiological resource use. Electrophysiological measurements indicated significantly more stable stress responses in plants subjected to iLEDs and hLEDs as compared to HPS and control treatments, indicating the effectiveness of LED light spectra in mitigating stress-related physiological impacts. Furthermore, compact growth and shorter stem internodes were observed under iLEDs as well as hLEDs, highlighting the spectral effects on photomorphogenesis, likely caused by a balanced light spectrum. HPS lighting achieved the highest yield (42.86 kg m−2) but at a significant environmental cost, with 342.65 kg CO2e m−2 emissions compared to 204.29 kg CO2e m−2 for iLEDs, with competitive yield of 38.84 kg m−2. Economic analysis revealed that iLEDs also offered the most cost-effective solution due to lower energy consumption and extended lifespan. This study focused on the interaction between light spectra, photosynthetic performance, stress resilience, and resource efficiency, advancing sustainable strategies for energy-efficient food production in CEA systems. [ABSTRACT FROM AUTHOR]

In recent years, an increase in the frequency of low-sunlight conditions due to climate change has resulted in a decline in the yield and quality of crops for greenhouse farmers, leading to significant challenges in maintaining optimal plant growth. The crop growth model can be used to predict changes in cucumber yield in response to variations in sunlight, which can help efficiently address sunlight shortages. The objective of this study was to improve and validate the model for predicting cucumber yield under different light environment conditions, including shading and supplemental lighting. The model comprises three steps: LAI prediction, daily assimilate yield prediction, and fruit yield prediction, each of which involves modifying the coefficients applied to suit the cucumber cultivar and environment condition. The improved model demonstrated a high degree of accuracy in predicting cucumber yields in the control and low-sunlight treatments (10, 20, and 30% shading), with a coefficient of determination (R2) > 0.98. When supplemental lighting was incorporated into the control and shading treatments, the accuracy of the improved model in predicting cucumber yield was also high, with a coefficient of determination (R2) > 0.99. The model also accurately predicted the decrease in cucumber fruit yield under low-sunlight conditions (shading treatments) and the increase in yield due to supplemental lighting. The findings of this study indicate that the improved cucumber yield prediction model can be applied to assess the efficacy of yield reduction in low-sunlight conditions and the potential for yield enhancement through supplemental lighting. [ABSTRACT FROM AUTHOR]

We conducted an analysis on the combined effects of two light conditions (L1: greenhouse natural lighting; L2: greenhouse natural lighting plus supplemental lighting (SL)) and three nutrient solution concentrations (EC, NS1: 3.2 dS/m; NS2: 3.7 dS/m; NS3: 4.2 dS/m) on the growth, fruit production, and quality of two cherry tomato cultivars with different fruit coloring ('Baiyu' and 'Qianxi'). The plants subjected to NS2 exhibited enhanced growth, photosynthetic parameters, and fruit production. The utilization of SL further enhanced stem diameter, leaf number, and single fruit weight, resulting in higher fruit weight per plant in 'Baiyu', which was not observed in 'Qianxi'. The growth, fruit size, and fruit weight of both cultivars cultivated under NS3 conditions were suppressed, while these fruits exhibited elevated levels of total soluble solids (TSS), soluble sugars, vitamin C, polyphenols, fructose, glucose, sucrose, citric acid, and carotenoids. These levels were further enhanced by SL treatment. The improvement of fruit quality through the application of SL was found to be cultivar and EC dependent. In 'Baiyu', SL at NS1 significantly enhanced the accumulation of fruit water, minerals (N, P, K, Ca, and Mg), TSS, vitamin C, fructose, sucrose, and carotenoids. However, this effect was not observed in 'Qianxi'. The combination of SL and EC 4.2 dS/m (NS3) generally contributes to the enhancement of fruit quality, while SL and EC 3.7 dS/m can ensure consistent fruit production. The yellowish-white fruit cultivar exhibited higher levels of soluble sugars, vitamin C, and polyphenols under L2NS3 conditions compared to the red fruit cultivar, whereas the carotenoid content showed an opposite trend. The findings are anticipated to establish a theoretical foundation for the consistent annual cultivation of cherry tomatoes in protected horticultural settings. [ABSTRACT FROM AUTHOR]

Because of the burgeoning year-round demand, greenhouse growers across the United States are increasingly becoming interested in producing specialty cut flowers for local and regional markets. However, outdoor or high tunnel production is not possible year-round in northern latitudes because of low temperatures and radiation intensities experienced during the winter and early spring. Additionally, natural short days in these seasons can limit which photoperiodic crops can be grown. Thus, our objectives were to quantify the influence of the photoperiod and daily light integral (DLI) on greenhouse-grown dianthus 'Amazon Neon Cherry' and 'Amazon Rose Magic' (Dianthus barbatus interspecific) cut flowers during the young plant and finishing stages. Seeds of both cultivars were sown under 9-, 10-, 11-, 12-, 13-, 15-, or 16-hour photoperiods and a DLI of either ≈5 or 10 mol.m-2.d-1. After 4 weeks, seedlings from several young-plant photoperiods were distributed across 11-, 12-, 13-, 14-, 15-, or 16-hour photoperiods or a 4-hour night interruption (NI) under a DLI of either ≈5 (low) or 14 (moderate) mol.m-2.d-1 for finishing. The young plant photoperiod generally had a statistical, but not commercial, influence on development and finished cut flower quality, whereas a 16-h finishing photoperiod marginally hastened development compared with an 11-hour finishing photoperiod. Additionally, stems were 11 to 13 cm longer when finished under the 16-hour photoperiod compared with those finished under the 11-hour photoperiod. Day length minimally influenced the time to flower and harvest, indicating a day-neutral flowering response. However, plants finished under a moderate DLI reached visible flower bud and were harvestable 9 to 10 days earlier than those finished under a low DLI. Additionally, ≈99% of cut flowers finished under a moderate DLI were harvestable, whereas only up to 32% and 57% of dianthus 'Amazon Rose Magic' and 'Amazon Neon Cherry', respectively, finished under a low DLI were harvestable. Although finished stem lengths were comparable between DLI treatments, cut flower stems were up to 29.6% thicker under a moderate DLI. These findings indicate that high-quality greenhouse-grown dianthus 'Amazon Neon Cherry' and 'Amazon Rose Magic' cut flowers can be produced when grown under any photoperiod between 9 and 16 hours for 4 weeks (during the young plant stage) and finished under any photoperiod between 11 and 16 hours or a 4-hour NI during finishing. If longer stems are desired, then plants can be finished under a 16-hour photoperiod. Young plants should be grown under a moderate DLI $10 mol.m-2.d-1 to promote biomass accumulation and reduce the young plant crop time. Additionally, plants should be finished under a moderate DLI $14 mol.m-2.d-1 to reduce crop time and increase stem thickness and yield. [ABSTRACT FROM AUTHOR]

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Antimony (III)‐containing halide hybrids possess a distinctive stereoactivity with a 5s2 lone pair, which further induces significant structural distortions upon light excitation. Herein disordered dis‐[TPPen]2SbBr5 (TPPen = triphenylpentylphosphonium) and ordered ord‐[TPPen]2SbBr5, have been synthesized and exhibit self‐trapped excitons (STEs) emissions in the red‐to‐near infrared (NIR) range. Benefiting from a high distortion degree of STEs confined within the [SbBr5]2− unit and the pronounced alterations in the Sb─Br bond lengths upon blue‐light excitation, dis‐[TPPen]2SbBr5 achieves a greater level of excited state distortion and a larger Stokes shift than those of ord‐[TPPen]2SbBr5. The fabrication of blue light excited NIR light‐emitting device based on dis‐[TPPen]2SbBr5 demonstrates the prospective application in night vision supplemental lighting and non‐destructive examination. This work provides valuable molecular design strategies for the NIR luminescent materials in hybrid metal halides. [ABSTRACT FROM AUTHOR]

Lighting is a fundamental driver of plant productivity in controlled-environment agriculture (CEA), directly affecting physiological processes, resource efficiency, and sustainability. This study evaluates the effects of distinct lighting systems, industrial Light-Emitting Diodes (iLEDs), horticultural LEDs (hLEDs), high-pressure sodium (HPS) lamps, and controls (no supplemental light), each providing unique light spectra, on cucumber (Cucumis sativus L.) growth, physiology, and environmental impact under a controlled light intensity of 250 µmol m−2 s−1 in a commercial CEA setup. The results indicated that iLEDs enhance intrinsic water use efficiency (35.65 µmol CO2/mol H2O) and reduce transpiration, reflecting superior physiological resource use. Electrophysiological measurements indicated significantly more stable stress responses in plants subjected to iLEDs and hLEDs as compared to HPS and control treatments, indicating the effectiveness of LED light spectra in mitigating stress-related physiological impacts. Furthermore, compact growth and shorter stem internodes were observed under iLEDs as well as hLEDs, highlighting the spectral effects on photomorphogenesis, likely caused by a balanced light spectrum. HPS lighting achieved the highest yield (42.86 kg m−2) but at a significant environmental cost, with 342.65 kg CO2e m−2 emissions compared to 204.29 kg CO2e m−2 for iLEDs, with competitive yield of 38.84 kg m−2. Economic analysis revealed that iLEDs also offered the most cost-effective solution due to lower energy consumption and extended lifespan. This study focused on the interaction between light spectra, photosynthetic performance, stress resilience, and resource efficiency, advancing sustainable strategies for energy-efficient food production in CEA systems.

Anthocyanins are secondary metabolites classified as water-soluble, non-photosynthetic pigments with the potential ability to shield chloroplasts from excess light energy. This study investigated the morphological and physiological responses of six lettuce (Lactuca sativa) cultivars with different leaf anthocyanin contents grown in a greenhouse under different supplemental photosynthetic photon flux densities (PPFD). Cultivars 'Cherokee', 'Teodore', 'Rex', and 'Rouxai' decreased in specific leaf area with increasing PPFD, respectively. We observed that growth in cultivars with higher leaf anthocyanin content ('Cherokee' and 'Rouxai') increased with increasing PPFD. Light use efficiency (LUE) is an important physiological parameter affecting biomass accumulation, and cultivars 'Cherokee', 'Rex', 'Teodore', and 'Rouxai' had the highest LUE and shoot weight. We found that red lettuce varieties, especially 'Cherokee' and 'Rouxai', showed increased shoot dry weight as light intensity increased. Interestingly, these varieties also had the highest anthocyanin levels in their leaves. This suggests that higher anthocyanin content might contribute to the increased shoot dry weight under higher light intensity, although this was mainly evident in 'Cherokee'. [ABSTRACT FROM AUTHOR]

Supplementary lighting is essential to maintain year-round production in Iceland due to the extremely low natural light level in winter. In this research, the effects of high-pressure vapour sodium lamps (HPS) are compared to light emitting diodes (LED), both with similar photosynthetic photon flux density (PPFD). Strawberries (Fragaria x ananassa cv. ‘Sonata' and cv. ‘Magnum') were grown either under HPS lights or LEDs and 16°C/8°C (day/night). However, in the second winter, the day temperature was increased to 19°C under LEDs. The results showed that under the same temperature set points, the development of the flowers and the harvest was delayed by two weeks under LEDs due to a lower leaf, substrate and air temperature. However, when temperature set points were adapted, no delay under LEDs was observed. LEDs did not lead to higher yield, but to a higher energy use efficiency, while light use efficiency behaved contrary. Economic calculations clearly demonstrate that it is not justified to switch from HPS lights to LEDs. Instead, it is rather recommended to emphasise a high-yielding variety like Sonata in winter-growing of strawberries.

In recent years, an increase in the frequency of low-sunlight conditions due to climate change has resulted in a decline in the yield and quality of crops for greenhouse farmers, leading to significant challenges in maintaining optimal plant growth. The crop growth model can be used to predict changes in cucumber yield in response to variations in sunlight, which can help efficiently address sunlight shortages. The objective of this study was to improve and validate the model for predicting cucumber yield under different light environment conditions, including shading and supplemental lighting. The model comprises three steps: LAI prediction, daily assimilate yield prediction, and fruit yield prediction, each of which involves modifying the coefficients applied to suit the cucumber cultivar and environment condition. The improved model demonstrated a high degree of accuracy in predicting cucumber yields in the control and low-sunlight treatments (10, 20, and 30% shading), with a coefficient of determination (R2) > 0.98. When supplemental lighting was incorporated into the control and shading treatments, the accuracy of the improved model in predicting cucumber yield was also high, with a coefficient of determination (R2) > 0.99. The model also accurately predicted the decrease in cucumber fruit yield under low-sunlight conditions (shading treatments) and the increase in yield due to supplemental lighting. The findings of this study indicate that the improved cucumber yield prediction model can be applied to assess the efficacy of yield reduction in low-sunlight conditions and the potential for yield enhancement through supplemental lighting.

We conducted an analysis on the combined effects of two light conditions (L1: greenhouse natural lighting; L2: greenhouse natural lighting plus supplemental lighting (SL)) and three nutrient solution concentrations (EC, NS1: 3.2 dS/m; NS2: 3.7 dS/m; NS3: 4.2 dS/m) on the growth, fruit production, and quality of two cherry tomato cultivars with different fruit coloring (‘Baiyu’ and ‘Qianxi’). The plants subjected to NS2 exhibited enhanced growth, photosynthetic parameters, and fruit production. The utilization of SL further enhanced stem diameter, leaf number, and single fruit weight, resulting in higher fruit weight per plant in ‘Baiyu’, which was not observed in ‘Qianxi’. The growth, fruit size, and fruit weight of both cultivars cultivated under NS3 conditions were suppressed, while these fruits exhibited elevated levels of total soluble solids (TSS), soluble sugars, vitamin C, polyphenols, fructose, glucose, sucrose, citric acid, and carotenoids. These levels were further enhanced by SL treatment. The improvement of fruit quality through the application of SL was found to be cultivar and EC dependent. In ‘Baiyu’, SL at NS1 significantly enhanced the accumulation of fruit water, minerals (N, P, K, Ca, and Mg), TSS, vitamin C, fructose, sucrose, and carotenoids. However, this effect was not observed in ‘Qianxi’. The combination of SL and EC 4.2 dS/m (NS3) generally contributes to the enhancement of fruit quality, while SL and EC 3.7 dS/m can ensure consistent fruit production. The yellowish-white fruit cultivar exhibited higher levels of soluble sugars, vitamin C, and polyphenols under L2NS3 conditions compared to the red fruit cultivar, whereas the carotenoid content showed an opposite trend. The findings are anticipated to establish a theoretical foundation for the consistent annual cultivation of cherry tomatoes in protected horticultural settings.

Supplemental light is widely applied in greenhouses to promote the production and flavor of strawberries in global markets. The present selections of colored lights are, however, quite empirical or qualitative, from the perspective of photometry or colorimetry, which lacks precision. The accurate control of chromatic parameters of supplemental light and their chromatic influences on fruit quality have been under-studied. In this study, color parameters including ten groups of correlated color temperatures (CCTs-2250 K, 2400 K, 2600 K, 2800 K, 3000 K, 3500 K, 4000 K, 4500 K, 5000 K, and 6000 K) and two groups of illuminances (600 lx and 1000 lx) of supplemental lights were precisely controlled using a digital color-coding method applied to LED supplemental lights, and the strawberry was irradiated with the LED supplemental light from December 2021 to March 2022 in facilities cultivation (greenhouse). Moreover, the irradiation time was 6 h per day (4:00 a.m.–7:00 a.m., 5:00 p.m.–8:00 p.m.). We systematically investigated the chromatic effects of supplemental light on five parameters of strawberries: plant height, single weight, fruit hardness, soluble solids, and titratable acids. The results showed that the supplemental light generally lowered the single weight by 14% and fruit hardness by 6%, and increased plant height by 21%, the contents of soluble solids by 7.4%, and titratable acids by 27%. The chromatic dependences of the five parameters were different and might be strengthened, weakened, or shifted by light illuminance. Our results demonstrated the beneficial roles of supplemental light in accelerating maturation and enhancing the flavor of strawberries in greenhouse cultivation. These results provided valuable guidance for the effective cultivation of strawberries. Moreover, the controlling method for accurate colors was ready for the implementation of supplemental lights in other fruits or plants. [ABSTRACT FROM AUTHOR]

Three primary factors that impact plant growth and development are light quantity, quality, and duration. Commercial growers can manipulate these parameters using light-emitting diodes (LEDs) to optimize biomass yield and plant quality. There is significant potential to synergize supplemental lighting (SL) parameters with seasonal variation of ambient sunlight to optimize crop light use efficiency (LUE), which could increase biomass while reducing SL electricity costs. To determine the best lighting characteristics and durations for different crops, particularly for enhancing the yield and nutritional quality of high-value specialty crops produced in greenhouses during the winter, a thorough efficacy comparison of progressive incremental daily light integrals (DLIs) using LED and high-pressure sodium (HPS) sources is required. The purpose of this study was to compare the effects of differential application timing and DLIs of supplemental blue (B)/red (R) narrowband wavelengths from LED lighting systems and HPS lamps on greenhouse hydroponic basil (Ocimum basilicum var. Genovese) production. We assessed edible biomass, nutrient bioaccumulation, and LUE. Nine light treatments included: one non-supplemented natural light (NL) control, two end-of-day (EOD) HPS treatments applied for 6 h and 12 h, five EOD 20B/ 80R LED treatments applied for 3 h, 6 h, 9 h, 12 h, 18 h, and one continuous LED treatment (24 h). Each SL treatment provided 100 µmol·m-2·s-1. The DLI of the NL control averaged 9.9 mol·m-2·d-1 during the growth period (ranging from 4 to 20 mol·m-2·d-1). SL treatments and growing seasons significantly impacted biomass and nutrient bioaccumulation; some SL treatments had lower yields than the non-supplemented NL control. January growing season produced the lowest fresh mass (FM) and dry mass (DM) values compared to November, which had the highest. Mineral analyses revealed that both growing seasons and lighting types impacted macro and micronutrient accumulation. Additionally, the efficiency of each treatment in converting electrical energy into biomass varied greatly. EOD supplements using LED and HPS lighting systems both have merits for efficiently optimizing yield and nutrient accumulation in basil; however, biomass and nutrient tissue concentrations highly depend on seasonal variation in ambient sunlight in conjunction with a supplement's spectral quality, DLI, and application schedule. [ABSTRACT FROM AUTHOR]

Protected cultivation is currently one of the main cultivation modes for grape production, but the long-term use of plastic film will have a certain negative impact on the light environment in vineyards, which in turn causes poor colouring, low sugar content and a lack of aroma in some red grape varieties. Supplementing light can be an effective way to mitigate these problems. In this study, vines of three red table grape varieties ('Summer Black', 'Xinyu' and 'Queen Nina') cultivated in a plastic greenhouse were supplemented with red, blue, white and red-blue light from veraison to harvest. All four supplemental light treatments increased the content of anthocyanins, sugars and volatile compounds in three grape varieties compared to CK (no supplemental lighting). Red-blue light treatment was the most favourable for the accumulation of anthocyanins and sugars, and the grapes treated with blue light had the highest content of volatile compounds. The grapes treated with red-blue light all obtained the highest composite scores via principal component analysis. For most of the sensory properties, the highest scores were obtained by the red-blue light-treated grapes. The results of this study will be useful in improving the colouring, sugar, and aroma content of grapes under protected cultivation. [ABSTRACT FROM AUTHOR]

The spectral quality of supplemental greenhouse lighting can directly influence aroma volatiles and secondary metabolic resource allocation (i.e., specific compounds and classes of compounds). Research is needed to determine species-specific secondary metabolic responses to supplemental lighting (SL) sources with an emphasis on variations in spectral quality. The primary objective of this experiment was to determine the impact of supplemental narrowband blue (B) and red (R) LED lighting ratios and discrete wavelengths on flavor volatiles in hydroponic basil (Ocimum basilicum var. Italian Large Leaf). A natural light (NL) control and different broadband lighting sources were also evaluated to establish the impact of adding discrete and broadband supplements to the ambient solar spectrum. Each SL treatment provided 8.64 mol.m-2.d-1 (100 µmol.m-2.s-1, 24 h.d-1) photon flux. The daily light integral (DLI) of the NL control averaged 11.75 mol.m-2.d-1 during the growth period (ranging from 4 to 20 mol.m-2.d-1). Basil plants were harvested 45 d after seeding. Using GC-MS, we explored, identified, and quantified several important volatile organic compounds (VOCs) with known influence on sensory perception and/or plant physiological processes of sweet basil. We found that the spectral quality from SL sources, in addition to changes in the spectra and DLI of ambient sunlight across growing seasons, directly influence basil aroma volatile concentrations. Further, we found that specific ratios of narrowband B/R wavelengths, combinations of discrete narrowband wavelengths, and broadband wavelengths directly and differentially influence the overall aroma profile as well as specific compounds. Based on the results of this study, we recommend supplemental 450 and 660 nm (± 20 nm) wavelengths at a ratio of approximately 10B/90R at 100-200 µmol.m-2.s-1, 12-24 h.d-1 for sweet basil grown under standard greenhouse conditions, with direct consideration of the natural solar spectrum and DLI provided for any given location and growing season. This experiment demonstrates the ability to use discrete narrowband wavelengths to augment the natural solar spectrum to provide an optimal light environment across variable growing seasons. Future experiments should investigate SL spectral quality for the optimization of sensory compounds in other high-value specialty crops. [ABSTRACT FROM AUTHOR]

The authors aimed to determine the plasma melatonin concentration in mares and their new-born foals in the early post-partum period. Blood samples were collected from the jugular vein of 53 mare-foal pairs within twelve hours after parturition. Plasma melatonin levels were measured by ELISA. The melatonin concentration, adjusted for the moment of parturition using a generalised linear model, was 34.58 pg mL−1 in mares. It was significantly lower (27.63 pg mL−1) in the new-born foals. However, the melatonin concentration declined differently by the end of the twelve hours, it decreased less in the offspring than in the mothers. An artificial light supplementation at the end of gestation reduced the melatonin concentration both in mares and their foals by about 10 pg mL−1, compared to the controls. An elevated melatonin production may be related to preparation of mares for parturition and ensures the chances of survival of offspring, therefore the melatonin may reach its peak at the moment of foaling regardless of its actual time. The effect of low melatonin concentration in new-born foals might be associated with the foal's health and subsequent performance. The need to monitor the melatonin concentration in the offspring justifies further studies. [ABSTRACT FROM AUTHOR]

Anthocyanins are secondary metabolites classified as water-soluble, non-photosynthetic pigments with the potential ability to shield chloroplasts from excess light energy. This study investigated the morphological and physiological responses of six lettuce (Lactuca sativa) cultivars with different leaf anthocyanin contents grown in a greenhouse under different supplemental photosynthetic photon flux densities (PPFD). Cultivars ‘Cherokee’, ‘Teodore’, ‘Rex’, and ‘Rouxai’ decreased in specific leaf area with increasing PPFD, respectively. We observed that growth in cultivars with higher leaf anthocyanin content (‘Cherokee’ and ‘Rouxai’) increased with increasing PPFD. Light use efficiency (LUE) is an important physiological parameter affecting biomass accumulation, and cultivars ‘Cherokee’, ‘Rex’, ‘Teodore’, and ‘Rouxai’ had the highest LUE and shoot weight. We found that red lettuce varieties, especially ‘Cherokee’ and ‘Rouxai’, showed increased shoot dry weight as light intensity increased. Interestingly, these varieties also had the highest anthocyanin levels in their leaves. This suggests that higher anthocyanin content might contribute to the increased shoot dry weight under higher light intensity, although this was mainly evident in ‘Cherokee’.

The spectral quality of supplemental greenhouse lighting can directly influence aroma volatiles and secondary metabolic resource allocation (i.e., specific compounds and classes of compounds). Research is needed to determine species-specific secondary metabolic responses to supplemental lighting (SL) sources with an emphasis on variations in spectral quality. The primary objective of this experiment was to determine the impact of supplemental narrowband blue (B) and red (R) LED lighting ratios and discrete wavelengths on flavor volatiles in hydroponic basil (Ocimum basilicum var. Italian Large Leaf). A natural light (NL) control and different broadband lighting sources were also evaluated to establish the impact of adding discrete and broadband supplements to the ambient solar spectrum. Each SL treatment provided 8.64 mol.m-2.d-1 (100 µmol.m-2.s-1, 24 h.d-1) photon flux. The daily light integral (DLI) of the NL control averaged 11.75 mol.m-2.d-1 during the growth period (ranging from 4 to 20 mol.m-2.d-1). Basil plants were harvested 45 d after seeding. Using GC-MS, we explored, identified, and quantified several important volatile organic compounds (VOCs) with known influence on sensory perception and/or plant physiological processes of sweet basil. We found that the spectral quality from SL sources, in addition to changes in the spectra and DLI of ambient sunlight across growing seasons, directly influence basil aroma volatile concentrations. Further, we found that specific ratios of narrowband B/R wavelengths, combinations of discrete narrowband wavelengths, and broadband wavelengths directly and differentially influence the overall aroma profile as well as specific compounds. Based on the results of this study, we recommend supplemental 450 and 660 nm (± 20 nm) wavelengths at a ratio of approximately 10B/90R at 100-200 µmol.m-2.s-1, 12-24 h.d-1 for sweet basil grown under standard greenhouse conditions, with direct consideration of the natural solar spectrum and DLI provided for any given location and growing season. This experiment demonstrates the ability to use discrete narrowband wavelengths to augment the natural solar spectrum to provide an optimal light environment across variable growing seasons. Future experiments should investigate SL spectral quality for the optimization of sensory compounds in other high-value specialty crops.

This study investigated the effects of supplemental inter-lighting on paprika (cv. Nagano RZ) in South Korea in summer using various LED light sources. The following LED inter-lighting treatments were used: QD-IL (blue + wide-red + far-red inter-lighting), CW-IL (cool-white inter-lighting), and B+R-IL (blue + red (1:2) inter-lighting). To investigate the effect of supplemental lighting on each canopy, top-lighting (CW-TL) was also used. Additionally, a control without supplemental lighting was included for comparison. Significant variations were observed in the plant growth indexes 42 days after treatment. The SPAD values and total chlorophyll content in the last period of cultivation were significantly higher than those of the control. In November, the marketable fruit yield was significantly higher than that of the control. QD-IL, CW-IL, and CW-TL resulted in significantly higher values of total soluble solids than the control, and CW-IL resulted in higher values of ascorbic acid content than the control. Regarding the economic analysis, CW-IL resulted in the highest net income rate (12.70%) compared with the control. Therefore, the light sources of CW-IL were assessed as suitable for supplemental lighting due to the highest total soluble solids, ascorbic acid content, and net income rate obtained. [ABSTRACT FROM AUTHOR]

Effects of extended photoperiods in red and blue LED supplemental lighting (SL) at constant photosynthetic photon flux density (PPFD) on growth, yield and quality of 'Patagonia' iceberg lettuce (Lactuca sativa var. capitata 'Iceberg') were evaluated. Different treatments were 14 hours of SL (T1), 16 hours of SL (T2) and 18 hours of SL (T3) under the similar ratio of 70:30 (R:B) at supplemented PPFD of 70 μmolm−2s−1 in comparison to treatment T4 i.e., No Supplemental Lighting (NSL) or control. The experiment was laid in a completely randomized design, and lettuce plants grown in soilless media in 100% complete nutrient solution under naturally ventilated greenhouse in winter season were planted in six replicates per treatment. Supplemental lighting was only used when the outside solar radiation dropped below 300 W/m2. The average temperature and relative humidity were within the range of 11.8–25 °C and 66.3–88.3%, respectively. The results indicate that growth parameters enhanced in respect of increased photoperiods. Yield was significantly different in all the treatments with highest value of 12.8 Kg/m2 under treatment T3 followed by 12.0 Kg/m2, 11.1 Kg/m2 and 10.3 Kg/m2 under T2, T1 and T4, respectively. Plants raised under SL treatments matured earlier in comparison to control. Treatment T3 significantly raised quality of lettuce in terms of L-ascorbic acid content, firmness, total phenolic content, DPPH radical scavenging activity and total soluble solids. Our findings demonstrate that extended photoperiods in supplemental LED lighting systems could improve growth, increase yield and enhance quality of iceberg lettuce grown in soilless media under protected cultivation. [ABSTRACT FROM AUTHOR]

Supplemental light is widely applied in greenhouses to promote the production and flavor of strawberries in global markets. The present selections of colored lights are, however, quite empirical or qualitative, from the perspective of photometry or colorimetry, which lacks precision. The accurate control of chromatic parameters of supplemental light and their chromatic influences on fruit quality have been under-studied. In this study, color parameters including ten groups of correlated color temperatures (CCTs-2250 K, 2400 K, 2600 K, 2800 K, 3000 K, 3500 K, 4000 K, 4500 K, 5000 K, and 6000 K) and two groups of illuminances (600 lx and 1000 lx) of supplemental lights were precisely controlled using a digital color-coding method applied to LED supplemental lights, and the strawberry was irradiated with the LED supplemental light from December 2021 to March 2022 in facilities cultivation (greenhouse). Moreover, the irradiation time was 6 h per day (4:00 a.m.–7:00 a.m., 5:00 p.m.–8:00 p.m.). We systematically investigated the chromatic effects of supplemental light on five parameters of strawberries: plant height, single weight, fruit hardness, soluble solids, and titratable acids. The results showed that the supplemental light generally lowered the single weight by 14% and fruit hardness by 6%, and increased plant height by 21%, the contents of soluble solids by 7.4%, and titratable acids by 27%. The chromatic dependences of the five parameters were different and might be strengthened, weakened, or shifted by light illuminance. Our results demonstrated the beneficial roles of supplemental light in accelerating maturation and enhancing the flavor of strawberries in greenhouse cultivation. These results provided valuable guidance for the effective cultivation of strawberries. Moreover, the controlling method for accurate colors was ready for the implementation of supplemental lights in other fruits or plants.

Far-red light has been included in horticultural light sources due to its physiological activity related to phytochrome-mediated responses. Recent studies have shown that adding far-red light to red and blue inter-lighting LEDs improves the growth and production of greenhouse tomatoes. However, in long-term cultivation, the effects of inter-lighting with additional far-red light may vary according to the seasonal light environment. This study aims to investigate the effect of adding far-red light to red and blue inter-lighting on growth and yield of sweet pepper in winter and summer. Sweet pepper (Capsicum annuum L. cv. Kori) plants were grown in greenhouses for five months under average daily light integrals of 16.6 and 32.2 mol m− 2 day− 1 in winter and summer, respectively. The inter-lighting with adding 55 µmol m− 2 s− 1 of far-red light to 71 µmol m− 2 s− 1 of red and blue light (red:blue = 8:2). The shoot dry weight and fruit yields were 20% and 17% higher, respectively, with additional far-red in the winter, but no significant differences in growth, yield, or morphology were observed in the summer. In summer, stem length and leaf area of plants increased rapidly due to sufficient sun irradiance, resulting in a higher far-red fraction at the bottom canopy. Thus, the far-red fraction at the middle and bottom canopies would have been sufficient with sunlight alone. Moreover, additional far-red inter-lighting promotes a decrease in leaf photosynthetic capacity in the bottom canopies. Therefore, plant growth and morphology were not influenced by adding far-red to inter-lighting in the summer at our latitude. We concluded that the additional far-red could contribute to growth and yield of sweet peppers in insufficient light conditions, but this effect disappears in conditions with ample sunlight. [ABSTRACT FROM AUTHOR]

Supplementary lighting is essential to maintain year-round production in Iceland due to the extremely low natural light level in winter. In this research, the effects of high-pressure vapour sodium lamps (HPS) are compared to light emitting diodes (LED), both with similar photosynthetic photon flux density (PPFD). Strawberries (Fragaria x ananassa cv. 'Sonata' and cv. 'Magnum') were grown either under HPS lights or LEDs and 16°C/8°C (day/night). However, in the second winter, the day temperature was increased to 19°C under LEDs. The results showed that under the same temperature set points, the development of the flowers and the harvest was delayed by two weeks under LEDs due to a lower leaf, substrate and air temperature. However, when temperature set points were adapted, no delay under LEDs was observed. LEDs did not lead to higher yield, but to a higher energy use efficiency, while light use efficiency behaved contrary. Economic calculations clearly demonstrate that it is not justified to switch from HPS lights to LEDs. Instead, it is rather recommended to emphasise a high-yielding variety like Sonata in winter-growing of strawberries. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the micrometeorological conditions in a greenhouse, arrangements, use of photoselective meshes (Stage I), and supplementary lighting by an emitting diode (Stage II), in the production of pre-sprouted sugarcane seedlings. The first experimental arrangement had the use of red, white, freshnet, and control photoselective meshes. The second experiment consisted of the use of supplemental lighting based on the light-emitting diode (LED) in the red and blue (R/B) spectra, in the proportion of 90/10, 80/20, 70/30, and control. The micrometeorological monitoring in the cultivation modules, in the greenhouse, occurred from the recording of air temperature (Tair), relative humidity (RH), global solar radiation (GR), and photosynthetically active radiation (PAR), through a datalogger. The biometric variables of the seedlings were recorded at the beginning and the end of the experiments. Data were submitted to descriptive statistics, principal component analysis (PCA), and multiple regression models established. PAR and GR showed strong correlations for the control treatment (± 0.80 and ± 0.75, respectively) from the beginning to the end of the experiments. The multivariate regression models presented satisfactory adjustments for determining the PAR in the initial (76.03%) and final (71.75%) phases, for the leaf area index (LAI) at the beginning (76.41%), and final (89.36%) of the production cycle. Freshnet and white photoselective meshes provided the best biometric responses in the final stage of seedling development, while supplemental lighting R/B in the 80/20 ratio showed better seedling development in the initial stage of the experiment. [ABSTRACT FROM AUTHOR]

Protected cultivation is currently one of the main cultivation modes for grape production, but the long-term use of plastic film will have a certain negative impact on the light environment in vineyards, which in turn causes poor colouring, low sugar content and a lack of aroma in some red grape varieties. Supplementing light can be an effective way to mitigate these problems. In this study, vines of three red table grape varieties (‘Summer Black’, ‘Xinyu’ and ‘Queen Nina’) cultivated in a plastic greenhouse were supplemented with red, blue, white and red-blue light from veraison to harvest. All four supplemental light treatments increased the content of anthocyanins, sugars and volatile compounds in three grape varieties compared to CK (no supplemental lighting). Red-blue light treatment was the most favourable for the accumulation of anthocyanins and sugars, and the grapes treated with blue light had the highest content of volatile compounds. The grapes treated with red-blue light all obtained the highest composite scores via principal component analysis. For most of the sensory properties, the highest scores were obtained by the red-blue light-treated grapes. The results of this study will be useful in improving the colouring, sugar, and aroma content of grapes under protected cultivation.

To produce consistent and high-quality specialty cut flowers throughout the year, growers in temperate climates must utilize controlled environment greenhouses. Research-based information on photoperiod management and supplemental lighting for specialty cut flowers is limiting. Therefore, our objectives were (1) to determine the effect of photoperiod during the youngplant and finishing stages on floral initiation and morphology of witchgrass 'Frosted Explosion' (Panicum capillare) and marigold 'Xochi' (Tagetes erecta) and (2) to quantify the effect of daily light integral (DLI) on floral initiation and morphology of witchgrass during the finishing stage. Seeds of marigold and multi-seed pellets of witchgrass were sown and placed under 9-, 11- (marigold only), 12-, 13-, 14-, 15-, 16-, 18-, or 24-h photoperiods or a 9-h short day with a 4-h night interruption (NI) from 2200 to 0200 h. Plugs were distributed among 10-, 11-, 12-, 13-, 14-, 15-, or 16-h photoperiods or a 4-h NI, for finishing. Witchgrass was finished under a very low or moderate DLI of ≈3 or 10 mol·m-2·d1, respectively, while marigold was finished under a DLI of ≈10 mol·m-2·d-1. Marigold grown under a photoperiod ≥ 11 h or a 4-h NI during the young-plant stage and finished under an 11- or 12-h photoperiod had thick stems and consistently met the marketable stem length of ≥ 65 cm. Up to 29% and 107% more stems were harvestable under 11- and 12-h finishing photoperiods, respectively, compared to a 10-h finishing photoperiod. Marigold visible buds were delayed, and stems were not harvestable under photoperiods ≥ 13 h or a 4-h NI after 8 weeks. Young witchgrass plants grown under a photoperiod between 14- and 24-h or a 4-h NI and finished under photoperiods ≥ 14 h or a 4-h NI, and at least a moderate DLI, were reliably harvestable (≥ 50 cm long with a fully developed panicle). Witchgrass finished under day lengths < 13 h (rep. 1) or < 14 h (rep. 2) flowered prematurely and were roughly one-sixth the length of harvestable stems at an open flower. All witchgrass stems grown under a very low DLI were shorter and thinner than those grown under a moderate DLI, and none were harvestable. Therefore, we recommend growing marigold 'Xochi' youngplants under a photoperiod ≥ 11 h or a 4-h NI and finishing under a 12-h photoperiod. Additionally, witchgrass 'Frosted Explosion' young plants should be grown under a photoperiod ≥ 14 h or a 4-h NI and finished under photoperiods ≥ 14 h or a 4-h NI to prevent premature flowering. Witchgrass and marigold cut flowers should be finished under a DLI of ≥ 10 mol·m-2·d-1 for consistent production of high-quality stems. [ABSTRACT FROM AUTHOR]

Supplemental lighting with light-emitting diode (LED) lamps and/or high-pressure sodium (HPS) lamps was applied to increase the activity of the photosynthetic apparatus and thus productivity of greenhouse cucumber (Cucumis sativus L.) in a high-wire growing system. The colocalisation of the chlorophyll of PSII (located mainly in grana) and carotenoid fluorescence signals in chloroplasts of cucumber leaves was studied under confocal microscopy. Leaf anatomy and some chemical quality traits (dry matter, chlorophyll, carotenoids, total soluble solids, total sugars and nitrate reductase activity) as well as selected chlorophyll fluorescence parameters were also investigated and subjected to the multidimensional principal component analysis together with the data on fruit yield. Under LED lighting, a lower correlation between the occurrence of chlorophyll and carotenoid fluorescence signals was observed, especially in older (lower-located) leaves, which may have resulted from changes in the distribution of carotenoids within chloroplasts and/or relative concentrations of chlorophyll and carotenoids. Compared to toplighting with HPS lamps, most commonly used in commercial greenhouse cucumber production, the application of LED interlighting, especially in combination with LED toplighting, led to the increase in chlorophyll and carotenoid content and photosynthetic performance index in older leaves, which was related to the increased cucumber productivity. [ABSTRACT FROM AUTHOR]

Recent advances in light emitting diode (LED) technology have provided exciting opportunities for plant lighting applications, and it is expected that LED lighting will soon overtake the still common use of high-intensity discharge (HID) lighting technology. Because LED lighting offers novel capabilities, extensive research is needed to identify optimal lighting practices for the large number of crops grown by commercial greenhouse growers. Plant scientists and growers facing decisions about plant lighting systems do not always have sufficient information about lamp performance characteristics. In this paper, we reported on various technical performance characteristics for 18 lamp types commonly used for plant production, and compared these characteristics with the characteristics of sunlight. The results showed a substantial range of performance characteristics, highlighting the importance of a careful assessment before selecting a light source for horticultural applications. The data presented in this paper can be used to assess the suitability of a specific light source for a particular horticultural application.

To produce consistent and high-quality specialty cut flowers throughout the year, growers in temperate climates must utilize controlled environment greenhouses. Research-based information on photoperiod management and supplemental lighting for specialty cut flowers is limiting. Therefore, our objectives were (1) to determine the effect of photoperiod during the young-plant and finishing stages on floral initiation and morphology of witchgrass ‘Frosted Explosion’ (Panicum capillare) and marigold ‘Xochi’ (Tagetes erecta) and (2) to quantify the effect of daily light integral (DLI) on floral initiation and morphology of witchgrass during the finishing stage. Seeds of marigold and multi-seed pellets of witchgrass were sown and placed under 9-, 11- (marigold only), 12-, 13-, 14-, 15-, 16-, 18-, or 24-h photoperiods or a 9-h short day with a 4-h night interruption (NI) from 2200 to 0200 h. Plugs were distributed among 10-, 11-, 12-, 13-, 14-, 15-, or 16-h photoperiods or a 4-h NI, for finishing. Witchgrass was finished under a very low or moderate DLI of ≈3 or 10 mol⋅m–2⋅d–1, respectively, while marigold was finished under a DLI of ≈10 mol⋅m–2⋅d–1. Marigold grown under a photoperiod ≥ 11 h or a 4-h NI during the young-plant stage and finished under an 11- or 12-h photoperiod had thick stems and consistently met the marketable stem length of ≥ 65 cm. Up to 29% and 107% more stems were harvestable under 11- and 12-h finishing photoperiods, respectively, compared to a 10-h finishing photoperiod. Marigold visible buds were delayed, and stems were not harvestable under photoperiods ≥ 13 h or a 4-h NI after 8 weeks. Young witchgrass plants grown under a photoperiod between 14- and 24-h or a 4-h NI and finished under photoperiods ≥ 14 h or a 4-h NI, and at least a moderate DLI, were reliably harvestable (≥ 50 cm long with a fully developed panicle). Witchgrass finished under day lengths < 13 h (rep. 1) or < 14 h (rep. 2) flowered prematurely and were roughly one-sixth the length of harvestable stems at an open flower. All witchgrass stems grown under a very low DLI were shorter and thinner than those grown under a moderate DLI, and none were harvestable. Therefore, we recommend growing marigold ‘Xochi’ young plants under a photoperiod ≥ 11 h or a 4-h NI and finishing under a 12-h photoperiod. Additionally, witchgrass ‘Frosted Explosion’ young plants should be grown under a photoperiod ≥ 14 h or a 4-h NI and finished under photoperiods ≥ 14 h or a 4-h NI to prevent premature flowering. Witchgrass and marigold cut flowers should be finished under a DLI of ≥ 10 mol⋅m–2⋅d–1 for consistent production of high-quality stems.

In indoor environments such as hotels, the light intensity is generally insufficient for managing plants, and flower buds often fail to open. Lamps placed above (downward lighting) take up space. We assessed the applicability of lighting from underneath (upward lighting) for the indoor management of roses. We grew plants indoors in dim light for 2 weeks under three conditions: 1) without supplemental lighting, 2) with downward light-emitting diode (LED) lighting, and 3) with LED lighting. We quantified photosynthetic components (chlorophyll and rubisco) and the maximum quantum yield of photosystem II (Fv/Fm, an indicator of plant health) to determine the effects of each treatment on the quality and photosynthetic abilities of the leaves. We determined the ratios of dead and opened flower buds to elucidate the effects of supplemental lighting on flower bud maturation. Management without supplemental lighting decreased the number of flowers and resulted in lower-leaf senescence. Downward LED lighting promoted blooming but also resulted in lower-leaf senescence. However, upward LED lighting promoted blooming and maintained the photosynthetic abilities of the leaves, including the lower leaves. This study shows a strong case for using upward LED lighting in appropriate settings for indoor plant management and LED-based horticulture.

Supplemental interlighting is commonly used in modern greenhouses to improve light deficiency, but the light spectrum affects fruit quality and color change. This study aimed to analyze the effect of interlighting with red, blue, and additional far-red light on the fruit qualities and carotenoid contents of red and yellow sweet peppers (Capsicum annuum L.). Three light treatments were applied: natural light (NL), NL with red + blue LED interlighting (71 μmol m–2 s–1) (RB), and RB with far-red light (55 μmol m–2 s–1) (RBFR). Ascorbic acid, free sugars, and individual carotenoid content were quantified with HPLC analysis. Fruits were sampled on 2020.11.14 (Group 1) and 2021.01.03 (Group 2) from the plants grown under average light intensities of 335.9 and 105.6 μmol m–2 s–1, respectively. In the overall period, total yields in RB and RBFR were 22 and 33% higher than those in NL in red fruits and 2 and 21% higher in yellow fruits, respectively. In both colored fruits, ascorbic acid, total soluble sugar, and carotenoid content were higher in RB and RBFR than NL. In Group 1, ascorbic acid and total soluble sugar were significantly different between RB and RBFR only in red fruits. In Group 2, ascorbic acids in red and yellow fruits were 9 and 3% higher in RBFR than RB but total soluble sugars were 4 and 2% lower, respectively. Carotenoid contents in red and yellow fruits were 3.0- and 2.1-fold higher in RB and 2.0- and 1.4-fold higher in RBFR than those in NL, respectively. In this study, interlighting had a significant impact on fruit quality in Group 2, mainly due to the increase in the ratio of interlighting to total light by seasonal changes. In particular, red and yellow fruit yields were 9% and 19% higher in RBFR than RB, but carotenoid contents were 26 to 9% lower, respectively. This result exhibited that additional far-red lighting has a trade-off relationship between fruit yield and carotenoid content. Thus, it is necessary to provide an adequate light spectrum according to a specific cultivation purpose, such as improving yield or accumulating plastids in fruits. [ABSTRACT FROM AUTHOR]

Supplemental interlighting is commonly used in modern greenhouses to improve light deficiency, but the light spectrum affects fruit quality and color change. This study aimed to analyze the effect of interlighting with red, blue, and additional far-red light on the fruit qualities and carotenoid contents of red and yellow sweet peppers (Capsicum annuum L.). Three light treatments were applied: natural light (NL), NL with red + blue LED interlighting (71 μmol m–2 s–1) (RB), and RB with far-red light (55 μmol m–2 s–1) (RBFR). Ascorbic acid, free sugars, and individual carotenoid content were quantified with HPLC analysis. Fruits were sampled on 2020.11.14 (Group 1) and 2021.01.03 (Group 2) from the plants grown under average light intensities of 335.9 and 105.6 μmol m–2 s–1, respectively. In the overall period, total yields in RB and RBFR were 22 and 33% higher than those in NL in red fruits and 2 and 21% higher in yellow fruits, respectively. In both colored fruits, ascorbic acid, total soluble sugar, and carotenoid content were higher in RB and RBFR than NL. In Group 1, ascorbic acid and total soluble sugar were significantly different between RB and RBFR only in red fruits. In Group 2, ascorbic acids in red and yellow fruits were 9 and 3% higher in RBFR than RB but total soluble sugars were 4 and 2% lower, respectively. Carotenoid contents in red and yellow fruits were 3.0- and 2.1-fold higher in RB and 2.0- and 1.4-fold higher in RBFR than those in NL, respectively. In this study, interlighting had a significant impact on fruit quality in Group 2, mainly due to the increase in the ratio of interlighting to total light by seasonal changes. In particular, red and yellow fruit yields were 9% and 19% higher in RBFR than RB, but carotenoid contents were 26 to 9% lower, respectively. This result exhibited that additional far-red lighting has a trade-off relationship between fruit yield and carotenoid content. Thus, it is necessary to provide an adequate light spectrum according to a specific cultivation purpose, such as improving yield or accumulating plastids in fruits.

Recently, many sports stadiums have begun using high power lighting systems to help the grass grow on the playing surfaces. These lights supplement winter sunlight, which is sometimes insufficient due to the low elevation of the sun and shading from the surrounding walls. In many stadiums, grow lights are operated at night, and the waste light emissions from these stadiums are extraordinary in comparison to most other areas in the cities in which they are located. Here we present space-based observations of the radiance of fourteen stadiums located in towns and cities of varying sizes and in varying geographical locations across England which each have a Premier League football stadium. We show that stadiums have dramatically brightened (typically by factors of 2-5) in recent years compared to the situation in 2012. We also show that stadiums are often responsible for an important fraction of the total light emission of the cities they are in (often 10% or more, and in one case up to 30%). Because the light emissions from many English towns have been reducing in recent years, the overall fraction of light due to the stadiums is increasing. In some cases, total city emissions have actually increased due to the stadiums, undermining the environmental impact of reductions in radiance in the rest of the community. We believe that stadium grow lights are an excellent target for sustainable lighting initiatives, both because of their considerable environmental impact (especially when located near sensitive areas) and the possibility of high profile and successful waste light mitigation projects.

ABSTRACT Bell peppers are one of the most cultivated and consumed vegetables in Brazil, and their high production yield largely depends on the use of high-quality seedlings. Supplementary lighting using light-emitting diodes (LEDs) can help in the production of seedlings and improve their quality. This study aims to develop a fuzzy model to predict the agronomic parameters of bell pepper seedlings under different light intensities. Experimental data on the lighting levels and biometric responses of bell pepper seedlings were used to develop a fuzzy model, and the lighting levels defined in five sets were used as the input variable. The model was used to predict the output variables, namely the plant height, number of leaves, stem diameter, internode number, shoot fresh weight, and root fresh weight. The results indicated that the use of supplemental lighting at a level of 75 μmol m-2s-1 was the most beneficial, producing seedlings with more leaves, higher stem diameters, internode numbers, and fresh weights. The model error rates were satisfactory for the predicted values of all variables, demonstrating the usefulness of the fuzzy model for estimating the best lighting levels in the cultivation of bell pepper seedlings.

Brazil is one of the three largest beer producers in the world. Four basic ingredients are needed as raw material for the production of beer: water, malt, yeast, and hops (Humulus lupulus L.). Until recently, almost all of the hops in Brazil were imported from other countries. However, in the last decade, hop cultivation in Brazil has emerged due to the increase in the number of new craft breweries, which have demanded diversified raw material for the production of various types of beer. Hops is considered a short-day, temperate species, so the major challenge for the development of hop cultivation in Brazil, with high-yield capacity and with local typicity of bitterness and aroma, is the adaptation of cultivars to the photoperiod conditions in subtropical regions. This review addresses the history of hop cultivation in Brazil and characterizes the main climatic elements of three emerging subtropical growing regions located at different latitudes, such as air temperature, photoperiod, solar radiation, and water availability, to provide support for the development of new technologies for hop cultivation, including supplemental lighting, irrigation, and mulching. [ABSTRACT FROM AUTHOR]

Light emitting diodes (LEDs) can produce a wide range of narrowband wavelengths with varying intensities. Previous studies have demonstrated that supplemental blue (B) and red (R) wavelengths from LEDs impact plant development, physiology, and morphology. High-pressure sodium (HPS) lighting systems are commonly used in greenhouse production, but LEDs have gained popularity in recent years because of their improved energy efficiency and spectral control. Research is needed to determine the efficacy of supplementary B and R LED narrowband wavelengths compared with traditional lighting systems like HPS in terms of yield, quality, and energy consumption for a variety of greenhouse-grown high-value specialty crops. The objective of this study was to determine the impact of LED and HPS lighting on greenhouse hydroponic basil (Ocimum basilicum var. ‘Genovese’) biomass production and edible tissue nutrient concentrations across different growing seasons. Basil was chosen because of its high demand and value among restaurants and professional chefs. A total of eight treatments were used: one nonsupplemented natural light (NL) control; one HPS treatment; and six LED treatments (peaked at 447 nm/627 nm, ±20 nm) with progressive B/R ratios (10B/90R; 20B/80R; 30B/70R; 40B/60R; 50B/50R; and 60B/40R). Each supplemented light (SL) treatment provided 8.64 mol·m−2·d−1 (100 µmol·m−2·s−1, 24 h·d−1). The daily light integral (DLI) of the NL control averaged 9.5 mol·m−2·d−1 across all growing seasons (ranging from 4 to 18 mol·m−2·d−1). Relative humidity averaged 50%, with day/night temperatures averaging 27.4 °C/21.8 °C, respectively. LED treatments had the greatest total fresh biomass (FM) and dry biomass (DM) accumulation; biomass for LED treatments were 1.3 times greater on average than HPS, and 2 times greater than the NL control. Biomass partitioning revealed that the LED treatments had more FM and DM for the individual main stem, shoots, and leaves of each plant at varying levels. LED treatments resulted in greater height and main stem diameter. Some essential nutrient concentrations were impacted by SL treatments and growing season. An energy analysis revealed that on average, narrowband B/R LED treatments were 3 times more energy efficient at increasing biomass over HPS. LED treatments reduced SL energy cost per gram FM increase by 95% to 98% when compared with HPS. In addition, the rate of electricity consumption to biomass increase varied across LED treatments, which demonstrates that basil uses different B/R narrowband ratios at varying efficiencies. This experiment shows that spectral quality of both supplemental sources and natural sunlight impacts primary metabolic resource partitioning of basil. The application of LED lighting systems to supplement natural DLI and spectra during unfavorable growing seasons has the potential to increase overall biomass accumulation and nutrient concentrations in a variety of high-value specialty crops.

This study investigated the effects of supplemental inter-lighting on paprika (cv. Nagano RZ) in South Korea in summer using various LED light sources. The following LED inter-lighting treatments were used: QD-IL (blue + wide-red + far-red inter-lighting), CW-IL (cool-white inter-lighting), and B+R-IL (blue + red (1:2) inter-lighting). To investigate the effect of supplemental lighting on each canopy, top-lighting (CW-TL) was also used. Additionally, a control without supplemental lighting was included for comparison. Significant variations were observed in the plant growth indexes 42 days after treatment. The SPAD values and total chlorophyll content in the last period of cultivation were significantly higher than those of the control. In November, the marketable fruit yield was significantly higher than that of the control. QD-IL, CW-IL, and CW-TL resulted in significantly higher values of total soluble solids than the control, and CW-IL resulted in higher values of ascorbic acid content than the control. Regarding the economic analysis, CW-IL resulted in the highest net income rate (12.70%) compared with the control. Therefore, the light sources of CW-IL were assessed as suitable for supplemental lighting due to the highest total soluble solids, ascorbic acid content, and net income rate obtained.

Recently, many sports stadiums have begun using high power lighting systems to help the grass grow on the playing surfaces. These lights supplement winter sunlight, which is sometimes insufficient due to the low elevation of the sun and shading from the surrounding walls. In many stadiums, grow lights are operated at night, and the waste light emissions from these stadiums are extraordinary in comparison to most other areas in the cities in which they are located. Here we present space-based observations of the radiance of fourteen stadiums located in towns and cities of varying sizes and in varying geographical locations across England which each have a Premier League football stadium. We show that stadiums have dramatically brightened (typically by factors of 2-5) in recent years compared to the situation in 2012. We also show that stadiums are often responsible for an important fraction of the total light emission of the cities they are in (often 10% or more, and in one case up to 30%). In addition, the light emissions from many English towns have in fact been reducing in recent years. This means that the overall fraction of light due to the stadiums is increasing at an even faster rate than their growth in radiance. In some cases, total city emissions have actually increased due to the stadiums, undermining the environmental impact of reductions in radiance in the rest of the community. We believe that stadium grow lights are an excellent target for sustainable lighting initiatives, both because of their considerable environmental impact (especially when located near sensitive areas) and the possibility of high profile and successful waste light mitigation projects. [ABSTRACT FROM AUTHOR]

Recent advances in light emitting diode (LED) technology have provided exciting opportunities for plant lighting applications, and it is expected that LED lighting will soon overtake the still common use of high-intensity discharge (HID) lighting technology. Because LED lighting offers novel capabilities, extensive research is needed to identify optimal lighting practices for the large number of crops grown by commercial greenhouse growers. Plant scientists and growers facing decisions about plant lighting systems do not always have sufficient information about lamp performance characteristics. In this paper, we reported on various technical performance characteristics for 18 lamp types commonly used for plant production, and compared these characteristics with the characteristics of sunlight. The results showed a substantial range of performance characteristics, highlighting the importance of a careful assessment before selecting a light source for horticultural applications. The data presented in this paper can be used to assess the suitability of a specific light source for a particular horticultural application. [ABSTRACT FROM AUTHOR]

• In a subtropical climate, photoperiod manipulation allows two crops of hops a year. • Photoperiod extension with LED (>16.9 hr, <1 µmol m–2 s–1) inhibits flowering in hops. • Hop yield and quality vary between spring and fall seasons in the subtropics. • Hops have high phenological plasticity with no chilling requirement for bud break. Hops (Humulus lupulus L.) have an ancient history of cultivation in temperate climates primarily as an ingredient of beer. However, growing hops in subtropical or tropical climates has been challenging because of non-optimal day length conditions. We examined the potential of subtropical hop production with photoperiod manipulation. 'Cascade' hops were grown in Florida, United States with extended day length (>16.5 h) using light-emitting diode (LED) bulbs to inhibit flowering until sufficient vegetative growth was achieved. Phenology, plant growth, yield, and cone quality data were collected during the first two years after planting. With as little as 0.47 μmol m–2 s–1, photoperiod extension was effective in inhibiting flowering, while promoting vegetative growth. Uniform flowering was induced upon the discontinuation of photoperiod extension. As a result, plants achieved two growing cycles per year, with the spring and fall growing seasons running from February to July and July to December, respectively. Yield increased by 92 % from Year 1 to Year 2 but decreased by 37 % from the spring to fall growing season. The maximum yield was 465 kg ha–1 in Year 2 Spring. Cone quality was greatly affected by both year and season, with α acid, β acid, and total oil concentrations ranging from 2.7 % to 6.2 %, 1.9 % to 3.2 % and 0.14 to 0.53 mL/100 g, respectively. These results demonstrate that, with an aid of photoperiod manipulation for flowering control, 'Cascade' hops exhibit high phenological plasticity and acclimation capacity to subtropical climatic conditions. This study provides a foundation for developing the double-season hop production system in a subtropical climate. [ABSTRACT FROM AUTHOR]

ABSTRACT Sugarcane is considered one of the main alternatives for biofuel production and an important product of Brazilian agriculture, so it is indispensable to adopt new techniques for its cultivation and management. Thus, the present study aimed to evaluate the effect of the quality of supplemental lighting, based on light-emitting diode (LED), on the acclimation of pre-sprouted sugarcane seedlings in a protected environment. The experimental design was completely randomized, consisting of three supplemental LED lighting systems, with light proportions of 90% red + 10% blue (R:B 90/10), 80% red + 20% blue (R:B 80/20) and 70% red + 30% blue (R:B 70/30), and a control, with natural solar radiation, with 5 replicates. Multivariate principal component analysis was used based on the matrix of correlation between all variables (meteorological, physiological and biometric). It was found that the different LED lighting systems increased the photosynthetically active radiation; however, until 20 days after planting, the seedlings were little influenced by the supplemental lighting systems. At the end of the acclimation period, the R:B 80/20 lighting system was the most associated with the growth and size of sugarcane seedlings.

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For decisions on supplemental lighting a quantitative knowledge of the plants' responses to light under varying conditions is fundamental. In this study, we developed light dose-response curves of growth and morphological traits for Ocimum basilicum L. and examined the effects of light color (blue, red, and white plus far-red) and natural environment (season) on these curves. Four greenhouse experiments were conducted throughout the year to determine the efficiencies of the light regimes on growth and their effects on plant morphology. A special aspect was the photosynthetic efficiency of far-red light. Linear and monomolecular relationships were found for the relationships between plant traits and supplemental light dose. Traits related to biomass productivity increased linearly with light dose whereas some morphological characters showed a saturation behavior. Red light and white plus far-red light were more efficient in plant dry weight production than blue light, and the plants adapted differently to the light qualities: higher biomass under red light was related to a plant architecture more favorable for light capture, i.e., taller plants and bigger leaves. White plus far-red light, on the other hand, increased leaf mass per area (LMA) and light use efficiency (LUE). Blue light resulted in lowest plant light interception and LUE. Considering photosynthetic effects of near-infrared light (PPFD800, 400–800 nm) instead of photosynthetic photon flux density (PPFD700, 400–700 nm) led to strongly reduced efficiencies. Traits related to photosynthesis such as dry weight, LMA and LUE were particularly affected by PPFD800. There were no interactions between the efficiencies of the different light colors and the seasons. Efficiencies of all light regimes were significantly lower during summer compared to spring and winter. Higher dry weight production during summer compared to winter and spring were a consequence of increased light interception rather than changes in LUE. The observed differences in seasonal efficiencies were directly linked to the amount of natural light present as indicated by changes in the ratio of supplemental to natural light.

For decisions on supplemental lighting a quantitative knowledge of the plants' responses to light under varying conditions is fundamental. In this study, we developed light dose-response curves of growth and morphological traits for Ocimum basilicum L. and examined the effects of light color (blue, red, and white plus far-red) and natural environment (season) on these curves. Four greenhouse experiments were conducted throughout the year to determine the efficiencies of the light regimes on growth and their effects on plant morphology. A special aspect was the photosynthetic efficiency of far-red light. Linear and monomolecular relationships were found for the relationships between plant traits and supplemental light dose. Traits related to biomass productivity increased linearly with light dose whereas some morphological characters showed a saturation behavior. Red light and white plus far-red light were more efficient in plant dry weight production than blue light, and the plants adapted differently to the light qualities: higher biomass under red light was related to a plant architecture more favorable for light capture, i.e., taller plants and bigger leaves. White plus far-red light, on the other hand, increased leaf mass per area (LMA) and light use efficiency (LUE). Blue light resulted in lowest plant light interception and LUE. Considering photosynthetic effects of near-infrared light (PPFD800, 400–800 nm) instead of photosynthetic photon flux density (PPFD700, 400–700 nm) led to strongly reduced efficiencies. Traits related to photosynthesis such as dry weight, LMA and LUE were particularly affected by PPFD800. There were no interactions between the efficiencies of the different light colors and the seasons. Efficiencies of all light regimes were significantly lower during summer compared to spring and winter. Higher dry weight production during summer compared to winter and spring were a consequence of increased light interception rather than changes in LUE. The observed differences in seasonal efficiencies were directly linked to the amount of natural light present as indicated by changes in the ratio of supplemental to natural light. [ABSTRACT FROM AUTHOR]

The use of light-emitting diodes (LEDs) in commercial greenhouse production is rapidly increasing because of technological advancements, increased spectral control, and improved energy efficiency. Research is needed to determine the value and efficacy of LEDs in comparison to traditional lighting systems. The objective of this study was to establish the impact of narrowband blue (B) and red (R) LED lighting ratios on flavor volatiles in hydroponic basil (Ocimum basilicum var. “Genovese”) in comparison to a non-supplemented natural light (NL) control and traditional high-pressure sodium (HPS) lighting. “Genovese” basil was chosen because of its high market value and demand among professional chefs. Emphasis was placed on investigating concentrations of important flavor volatiles in response to specific ratios of narrowband B/R LED supplemental lighting (SL) and growing season. A total of eight treatments were used: one non-supplemented NL control, one HPS treatment, and six LED treatments (peaked at 447 nm/627 nm, ±20 nm) with progressive B/R ratios (10B/90R, 20B/80R, 30B/70R, 40B/60R, 50B/50R, and 60B/40R). Each SL treatment provided 8.64 mol ⋅ m−2 ⋅ d–1 (100 μmol ⋅ m–2 ⋅ s–1, 24 h ⋅ d–1). The daily light integral (DLI) of the NL control averaged 9.5 mol ⋅ m−2 ⋅ d–1 during the growth period (ranging from 4 to 18 mol ⋅ m−2 ⋅ d–1). Relative humidity averaged 50%, with day/night temperatures averaging 27.4°C/21.8°C, respectively. Basil plants were harvested 45 days after seeding, and volatile organic compound profiles were obtained by gas chromatography–mass spectrometry. Total terpenoid concentrations were dramatically increased during winter months under LED treatments, but still showed significant impacts during seasons with sufficient DLI and spectral quality. Many key flavor volatile concentrations varied significantly among lighting treatments and growing season. However, the concentrations of some compounds, such as methyl eugenol, were three to four times higher in the control and decreased significantly for basil grown under SL treatments. Maximum concentrations for each compound varied among lighting treatments, but most monoterpenes and diterpenes evaluated were highest under 20B/80R to 50B/50R. This study shows that supplemental narrowband light treatments from LED sources may be used to manipulate secondary metabolic resource allocation. The application of narrowband LED SL has great potential for improving overall flavor quality of basil and other high-value specialty herbs.

Shorter photoperiod and lower daily light integral (DLI) limit the winter greenhouse production. Extending the photoperiod by supplemental light increases biomass production but inhibits flowering in short-day plants such as Chrysanthemum morifolium. Previously, we reported that flowering in growth-chamber grown chrysanthemum with red (R) and blue (B) LED-light could also be induced in long photoperiods by applying only blue light during the last 4h of 15h long-days. This study investigates the possibility to induce flowering by extending short-days in greenhouses with 4h of blue light. Furthermore, flower induction after 4h of red light extension was tested after short-days RB-LED light in a growth-chamber and after natural solar light in a greenhouse. Plants were grown at 11h of sole source RB light (60:40) in a growth-chamber or solar light in the greenhouse (short-days). Additionally, plants were grown under long-days, which either consisted of short-days as described above extended with 4h of B or R light to long-days or of 15h continuous RB light or natural solar light. Flower initiation and normal capitulum development occurred in the blue-extended long-days in the growth-chamber after 11h of sole source RB, similarly as in short-days. However, when the blue extension was applied after 11h of full-spectrum solar light in a greenhouse, no flower initiation occurred. With red-extended long-days after 11h RB (growth-chamber) flower initiation occurred, but capitulum development was hindered. No flower initiation occurred in red-extended long-days in the greenhouse. These results indicate that multiple components of the daylight spectrum influence different phases in photoperiodic flowering in chrysanthemum in a time-dependent manner. This research shows that smart use of LED-light can open avenues for a more efficient year-round cultivation of chrysanthemum by circumventing the short-day requirement for flowering when applied in emerging vertical farm or plant factories that operate without natural solar light. In current year-round greenhouses’ production, however, extension of the natural solar light during the first 11 h of the photoperiod with either red or blue sole LED light, did inhibit flowering.

Brazil is one of the three largest beer producers in the world. Four basic ingredients are needed as raw material for the production of beer: water, malt, yeast, and hops (Humulus lupulus L.). Until recently, almost all of the hops in Brazil were imported from other countries. However, in the last decade, hop cultivation in Brazil has emerged due to the increase in the number of new craft breweries, which have demanded diversified raw material for the production of various types of beer. Hops is considered a short-day, temperate species, so the major challenge for the development of hop cultivation in Brazil, with high-yield capacity and with local typicity of bitterness and aroma, is the adaptation of cultivars to the photoperiod conditions in subtropical regions. This review addresses the history of hop cultivation in Brazil and characterizes the main climatic elements of three emerging subtropical growing regions located at different latitudes, such as air temperature, photoperiod, solar radiation, and water availability, to provide support for the development of new technologies for hop cultivation, including supplemental lighting, irrigation, and mulching.

Abstract Greenhouse agriculture is a highly efficient method of food production that can greatly benefit from supplemental electric lighting. The needed electricity associated with greenhouse lighting amounts to about 30% of its operating costs. As the light level of LED lighting can be easily controlled, it offers the potential to reduce energy costs by precisely matching the amount of supplemental light provided to current weather conditions and a crop’s light needs. Three simulations of LED lighting for growing lettuce in the south-east of the US using historical solar radiation data for the area were conducted. Lighting costs can be potentially reduced by approximately 60%.