Supplemental Lighting Research Articles

Supplemental lighting and CO2 enrichment on the growth, fruit quality, and yield of cucumber

Supplemental lighting and CO2 enrichment on the growth, fruit quality, and yield of cucumber

Partially Substituting Photosynthetic Photon Flux Density with Far-red Photons Differentially Alters Biomass Accumulation and Photochemical Efficiency of Greenhouse Lettuce

Adding far-red (FR) photons to a constant photosynthetic photon flux density (PPFD) alters photosynthesis, leaf morphology, and biomass accumulation of horticultural plants. However, the influences of partially substituting PPFD with FR photons under the same extended PPFD (ePPFD) on the growth of greenhouse lettuce (Lactuca sativa L.) is still unknown. In this study, loose-leaf lettuce (‘Dasusheng’) grown in a greenhouse in the fall was implemented using six supplementary light treatments including white plus red (WR) LEDs with substitutive FR photon flux density at 0, 10, 30, 50, 70, and 90 µmol·m−2·s−1 under the same ePPFD (WR139, WR129+FR10, WR109+FR30, WR89+FR50, WR69+FR70, and WR49+FR90, respectively). Lettuce grown with natural light only was designated as NL. The results indicated that supplementary light led to lower plant height, thicker leaves, higher biomass accumulation, higher vitamin C content, higher starch content, and higher total soluble sugar content in lettuce compared with those of lettuce grown under NL. Lettuce grown under WR139 resulted in a 40.0% decrease in plant height, 66.8% increase in leaf thickness, and 34.1% increase in shoot fresh weight compared with those of lettuce grown under NL. No significant differences were observed in leaf width, specific leaf area, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, soil plant analysis development value, apparent quantum yield, soluble protein content, and light use efficiency of lettuce among the WR139, WR129+FR10, and WR109+FR30 treatments. Furthermore, decreased trends were observed in the biomass accumulation and maximum net photosynthetic rate of lettuce with the increased substituted FR photon flux density. However, an opposite trend was found in the maximum photochemical quantum yield. In conclusion, partially substituting PPFD with FR photons at 10 to 30 μmol·m−2·s−1 had similar effects on the biomass accumulation and nutritional quality of greenhouse lettuce. The FR photons should be applied with the consideration of photon flux density because the results also demonstrated negative effects of excess substituted FR photons for PPFD.

Enhancing strawberry resilience to saline, alkaline, and combined stresses with light spectra: impacts on growth, enzymatic activity, nutrient uptake, and osmotic regulation

BackgroundThis study examines the effects of various complementary light spectra on the growth, development, antioxidant activity, and nutrient absorption in strawberry plants under stress conditions. Light-emitting diodes (LEDs) were used to provide specific wavelengths, including monochromatic blue (460 nm), monochromatic red (660 nm), a dichromatic mix of blue and red (1:3 ratio), full-spectrum white light (400–700 nm), and ambient light as a control (no LED treatment). The stress treatments applied were: control (no stress), salinity (80 mM NaCl), alkalinity (40 mM NaHCO₃), and a combined salinity/alkalinity condition.ResultsOur results indicated that complementary light spectra, especially red and blue/red, helped mitigate the adverse effects of stress on plant growth and development. These spectra improved plant tolerance by enhancing the activity of polyphenol oxidase and peroxidase enzymes and increasing starch accumulation in the leaves. Furthermore, under stress conditions, red and blue-red light significantly boosted fruit anthocyanin levels. Although stress elevated antioxidant activity, supplementary light reduced this activity by alleviating stress compared to ambient light. While stress led to increased Na and Cl ion concentrations in leaves, treatments with blue, red, and blue-red light minimized these harmful effects and promoted the absorption of beneficial ions such as K, Mg, Fe, and Cu.ConclusionsAdjusting light quality significantly influences the morphology and physiology of strawberry plants, underscoring the role of specific light spectra in promoting optimal growth under stress conditions.Clinical trial numberNot applicable

Cut Flower Yields and Qualities of Rosa hybrid L. Affected by Supplementary LED Lighting at Night under High Temperature and Low Light Intensity Conditions

Cut Flower Yields and Qualities of Rosa hybrid L. Affected by Supplementary LED Lighting at Night under High Temperature and Low Light Intensity Conditions

Optimization of trellis design and height for double-season hop (Humulus lupulus L.) production in a subtropical climate: Growth, morphology, yield, and cone quality during establishment years

Photoperiod manipulation using supplemental lighting enables double-season production of hops (Humulus lupulus L.) under subtropical climatic conditions. In Florida, United States, the spring growing season (Spring) is from February to June, and the fall growing season (Fall) is from June to November. To develop the optimum trellis for this unique hop production system, we examined the effects of two trellis designs (straight trellis and V-trellis) and three trellis heights (3.7, 4.6, and 5.5 m) on growth, morphology, yield, and cone quality of 'Cascade' hops grown in west central Florida. The straight trellis had two twines per hill installed on a top middle cable, whereas the V-trellis had four twines per hill installed on two top parallel cables. We trained 16 bines per hill for both trellises. Data were collected during establishment years: Year 1 and Year 2. Yield showed significant season × trellis height interaction effects. Surprisingly, yield was highest in Year 1 Spring and decreased by 45–74 % in the subsequent seasons. Increasing trellis height from 3.7 to 5.5 m increased yield by 78–215 %. On average, the V-trellis produced 24 % higher yield than the straight trellis. The 5.5-m V-trellis produced the highest annual yield of 1807 kg ha–1 in Year 1. Yield had a significant positive correlation with stem dry weight in Year 1 Spring and Year 2 Spring, but it had no significant correlation with bine number per hill, stem diameter, and internode length in any season. Cone quality showed significant seasonal variations. Total α acid concentration decreased from Spring to Fall in both years and recorded the highest value in Year 2 Spring. Similarly, total essential oil content was highest in Year 2 Spring. Except in Year 2 Fall, total α acid concentration (5.35–8.25 %) was within or above the normal range for ‘Cascade’. Compared to these seasonal variations, trellis design and height effects on cone quality were relatively small. These results suggest that, during establishment years, adopting a V-trellis design and increasing trellis height can maximize yield in subtropical hop production without compromising overall cone quality. Ongoing research will validate these findings in mature hop plants.

Effect of Supplemental Light for Leaves Development and Seed Oil Content in Brassica napus

Effect of Supplemental Light for Leaves Development and Seed Oil Content in Brassica napus

Effects of Different LED Spectra on the Antioxidant Capacity and Nitrogen Metabolism of Chinese Cabbage (Brassica rapa L. ssp. Pekinensis).

Light quality optimization is a cost-effective method for increasing leafy vegetable quality in plant factories. Light-emitting diodes (LEDs) that enable the precise modulation of light quality were used in this study to examine the effects of red-blue (RB), red-blue-green (RBG), red-blue-purple (RBP), and red-blue-far-red (RBF) lights on the growth, antioxidant capacity, and nitrogen metabolism of Chinese cabbage leaves, while white light served as the control (CK). Results showed that the chlorophyll, carotenoid, vitamin C, amino acid, total flavonoid, and antioxidant levels of Chinese cabbage were all significantly increased under RBP combined light treatment. Meanwhile, RBG combined light treatment significantly increased the levels of amino acids but decreased the nitrite content of Chinese cabbage. In addition, RBF combined light treatment remarkably increased the amino acid levels but decreased the antioxidant capacity of Chinese cabbage. In conclusion, the addition of purple light to red-blue light was effective in improving the nutritional value and antioxidant capacity of Chinese cabbage. This light condition can be used as a model for a supplemental lighting strategy for leafy vegetables in plant factory production.

Trait component analysis of lettuce in response to daily light integrals at two growth stages

AbstractLittle is known about the relative impact of lighting duration and light intensity on lettuce production, as well as whether daily light integrals (DLIs) play a significant role during different plant growth stages. Four DLIs were tested: 8.64, 11.52, 12.96, and 17.28 mol m−2 day−1 as supplemental lighting, which were obtained from a combination of supplemental light intensities at 200 and 300 µmol m−2 day−1 for 12 and 16 h. Sunlight was used as control. A direct correlation was observed between DLIs and yield, total fresh weight, and total dry weight. Under supplemental lighting, relative growth rate (RGR) increased due to an increase in net assimilation rate (NAR) rather than in leaf area ratio (LAR). Plants in the seedling stage were more sensitive to an elevation in DLI than in the head stage. This was confirmed by a greater increase in NAR compared to their corresponding control under the same DLI. Increasing DLI also improved lettuce quality via reducing nitrate and increasing protein content. Higher DLIs (12.96 and 17.28 mol m−2 day−1) led to a decrease in maximum quantum yield of photosystem II and an increase in performance index. In conclusion, manipulating RGR through NAR adjustments proved to be more effective than changes in LAR, and adjusting supplemental DLI at each stage was necessary to achieve a larger NAR and, consequently, a larger RGR.

Both the Positioned Supplemental or Night-Interruptional Blue Light and the Age of Leaves (or Tissues) Are Important for Flowering and Vegetative Growth in Chrysanthemum.

In this study, the effects of supplemental or night interruptional blue light (S-BL or NI-BL) positioning on morphological growth, photoperiodic flowering, and expression of floral genes in Chrysanthemum morifolium were investigated. Blue light-emitting diodes (LEDs) at an intensity of 30 μmol·m-2·s-1 photosynthetic photon flux density (PPFD) were used for 4 h either (1) to supplement the white LEDs at the end of the 10 h short-day (SD10 + S-BL4) and 13 h long-day conditions (LD13 + S-BL4), or (2) to provide night interruption in the SD10 (SD10 + NI-BL4) and LD13 (LD13 + NI-BL4). The S-BL4 or NI-BL4 was positioned to illuminate either the shoot tip, the youngest leaf (vigorously growing the third leaf from the shoot tip), or the old leaf (the third leaf from the stem base). In the text, they will be denoted as follows: SD10 + S-BL4-S, -Y, or -O; SD10 + NI-BL4-S, -Y, or -O; LD13 + S-BL4-S, -Y, or -O; LD13 + NI-BL4-S, -Y, or -O. Normally, the LD13 conditions enhanced more vegetative growth than the SD10 periods. The growth of leaves, stems, and branches strongly responded to the S-BL4 or NI-BL4 when it was targeted onto the shoot tip, followed by the youngest leaf. The SD10 + S-BL4 or +NI-BL4 on the old leaf obviously suppressed plant extension growth, resulting in the smallest plant height. Under LD13 conditions, the flowering-related traits were significantly affected when the S-BL4 or NI-BL4 was shed onto the youngest leaf. However, these differences do not exist in the SD10 environments. At the harvest stage, other than the non-flowered LD13 treatment, the LD13 + S-BL4 irradiating the youngest leaf induced the most flowers, followed by the shoot tip and old leaf. Moreover, LD13 + NI-BL4 resulted in the latest flowering, especially when applied to the shoot tip and old leaf. However, the SD10 + S-BL4 or + NI-BL4 irradiated the shoot tip, youngest leaf, or old leaf all significantly earlier and increased flowering compared to the SD10 treatment. Overall: (1) Generally, vegetative growth was more sensitive to photoperiod rather than lighting position, while, during the same photoperiod, the promotion of growth was stronger when the light position of S-BL4 or NI-BL4 was applied to the shoot tip or the youngest leaf. (2) The photoperiodic flowering of these short-day plants (SDPs) comprehensively responded to the photoperiod combined with blue light positioning. Peculiarly, when they were exposed to the LD13 flowering-inhibited environments, the S-BL4 or NI-BL4 shed onto the leaves, especially the youngest leaves, significantly affecting flowering.

The design and implementation of a smart greenhouse control system

Abstract Against the dual backdrop of continuously improving agricultural production levels and the global scarcity of water resources, countries worldwide are actively exploring the topic of water conservation. The development of an intelligent irrigation control system could make a significant contribution to water conservation efforts, while also helping to increase crop yields. This project adopts a modular design approach, utilizing sensors to collect real-time environmental data surrounding the crops. If the data falls outside the predefined optimal range for crop growth, the system automatically initiates irrigation, cooling, and supplemental lighting. The hardware design primarily consists of a data perception module and a control terminal module. After testing, the system runs stably and can accurately obtain information such as soil moisture, light intensity and ambient temperature, and basically realize the digital intelligent control of crop growing environment.

Phytochrome-dependent responsiveness to root-derived cytokinins enables coordinated elongation responses to combined light and nitrate cues

Plants growing at high densities can detect competitors through changes in the composition of light reflected by neighbours. In response to this far-red-enriched light, plants elicit adaptive shade avoidance responses for light capture, but these need to be balanced against other input signals, such as nutrient availability. Here, we investigated how Arabidopsis integrates shade and nitrate signalling. We unveiled that nitrate modulates shade avoidance via a previously unknown shade response pathway that involves root-derived trans-zeatin (tZ) signal and the BEE1 transcription factor as an integrator of light and cytokinin signalling. Under nitrate-sufficient conditions, tZ promotes hypocotyl elongation specifically in the presence of supplemental far-red light. This occurs via PIF transcription factors-dependent inhibition of type-A ARRs cytokinin response inhibitors. Our data thus reveal how plants co-regulate responses to shade cues with root-derived information about nutrient availability, and how they restrict responses to this information to specific light conditions in the shoot.

Supplemental ambient lighting intervention to improve sleep in Parkinson's disease: A pilot trial

ImportanceSleep disturbances in Parkinson's disease (PD) are common and often adversely affect quality of life. Light therapy has benefited sleep quality and mood outcomes in various populations but results to date with conventional light therapy boxes in PD patients have been mixed. We hypothesized that a passive lighting intervention, applied in the morning and designed to maximally affect the circadian system, would improve measures of sleep and mood in PD patients. MethodsIn this single-arm, within-subjects intervention study, baseline objective sleep (actigraphy), subjective sleep quality (questionnaires), and subjective mood (questionnaires) data were collected for 1 week. Lighting was then administered to participants via table/floor lamps installed in the home or via personal light therapy glasses for 2 h in the morning, 7 days per week, over the following 4-week period. Post-intervention data for the same outcomes were collected during the final week of the intervention period. ResultsAmong 20 participants (12 women, 8 men; mean [SD] age 72.1 [9.5] years, disease duration 9.0 [5.2] years), objective sleep duration increased significantly by 28.5 min (p = 0.029) and objective sleep time increased significantly by 19.9 min (p = 0.026). ConclusionPassive and easily administered lighting interventions for improving sleep in PD patients hold promise as a treatment for mitigating symptoms and improving quality of life in PD.

Influence of Combined Supplemental Lighting and Nutrient Solution Concentration on Fruit Production and Quality of Cherry Tomato

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.

An approach for modern gardening through monitoring and maintenance of plant health

The study explores the use of internet of things (IoT) devices in agriculture to improve sustainable practices and environmental concerns. It uses the ESP8266 microcontroller and the Blynk platform to create a revolutionary plant health monitoring and automated care system. The system is designed to handle continuous monitoring and plant maintenance in various environmental conditions. Sensors measuring light, temperature, humidity, and soil moisture are strategically placed to receive real-time data. The ESP8266 microcontroller analyzes this information and links it to the Blynk cloud for accessibility via mobile or web applications. The system is effective in monitoring ideal growing conditions, such as soil moisture and weather conditions. Automated care elements like irrigation and supplemental lighting have been shown to improve plant growth and health. The study contributes to smart farming by offering an affordable and easy way to automate and monitor plant health, demonstrating how IoT technologies can enhance agricultural practices, conserve resources, and enable remote management of plant ecosystems.

Quantifying Temperature Effects on Plant Development Rates and Quality of Compact Container-grown Pepper

The mean daily temperature effects on plant development rates and quality of compact container-grown pepper were evaluated. Compact pepper cultivars Fresh Bites Yellow and Hot Burrito were grown in greenhouses at 18 to 26 °C (Expt. 1) and 20 to 30 °C (Expt. 2) under supplemental high-pressure sodium lighting and a 16-hour photoperiod. The number of days to first open flower, to first ripe fruit, and from flower to ripe fruit were measured and the development rates calculated by taking the reciprocal (e.g., 1/day). Temperature effects were predicted by fitting a nonlinear exponential function that included the base temperature (Tmin) and maximum developmental rate (Rmax) parameters. Plant quality attributes were measured during Expt. 2. As the temperature increased, the times to flower and fruit decreased (i.e., developmental rates increased) for both cultivars. The estimated Tmin was 13.3 °C for ‘Fresh Bites Yellow’, and that for ‘Hot Burrito’ was 9.3 °C, whereas the Rmax was similar between cultivars (averages of 0.0488 at flower, 0.0190 at fruit, and 0.0252 from flower to fruit). ‘Fresh Bites Yellow’ and ‘Hot Burrito’ grown at ≈25 °C had a relatively short crop time, compact canopy, large fruit size, and high number of fruits per plant at finish. Compact peppers are new crops being grown by greenhouse floriculture operations for their ornamental and edible value, and the information from this study can help growers schedule these crops to meet critical market windows and determine the impacts of changing the growing temperature on crop timing and quality.

Optimization framework of clean heat and CO2 supply for agricultural greenhouses exploiting industrial symbiosis

The rising demand for greenhouse cultivation poses a challenge in providing environmentally friendly energy to maintain favorable greenhouse indoor conditions. This research presents an optimization model to identify cost-optimal symbiotic pathways to replace the import of three key greenhouse crops (tomato, cucumber, lettuce) with local greenhouse production. The proposed solutions involve greenhouses that can meet these crops' heat and CO2 demands via industrial symbiosis. Switzerland is investigated as the case study, and the (waste) heat suppliers are municipal solid waste incinerators, cement production plants and biogas plants. Upgrading biomethane production plants are also considered potential CO2 suppliers. The objective is to minimize the discounted cost when replacing 25%–100 % of vegetable imports with local agricultural greenhouses, considering availability of suitable land as well as waste heat and CO2 suppliers. Optimization results suggest prioritizing northeast and west Switzerland for greenhouse development, due to the availability of suitable land and proximity of waste heat and CO2 suppliers. Waste incinerators could provide 50%–70 % of the necessary heat, while Organic Rankine cycle in cement plants could generate 63 % of the electricity of supplementary lighting demand of greenhouses. While tailored for Switzerland, the optimization framework's general formulation can be adapted also to other regions to optimize greenhouses' heat and CO2 demands. The optimization code is provided open source for associated applications.

Effects of daytime LED supplemental lighting on strawberry growth and yield under subtropical climate

Effects of daytime LED supplemental lighting on strawberry growth and yield under subtropical climate

Varying Light Intensities Affect Lettuce Growth and Physiology in Controlled Indoor Environments

Agriculture in controlled environments has gained popularity over time. Compared to traditional agriculture, controlled environments emerge as an alternative to mitigate the negative impacts of conventional farming methods. However, controlled environment agriculture, particularly plant factories with artificial lighting, incurs higher electricity costs, primarily for supplemental lighting and dehumidification of the cultivation area. Given these high costs, it is crucial to understand how efficiently plants utilize available light to convert it into biomass. This understanding can be used to design lighting strategies to reduce electricity usage. In this study, we cultivated ‘Rex’ lettuce (Lactuca sativa) plants on a soilless substrate and used an ebb-and-flow system for irrigation and fertilization. Plants grew in varying photosynthetic photon flux density (PPFD) levels ranging from 125 to 375 µmol·m−2·s−1 and were assessed for various physiological responses. Our findings revealed that plants exposed to higher light levels exhibited greater final dry weight, increased photosynthetic activity, higher water use efficiency, and accelerated growth compared to those under lower light conditions. Notably, plants subjected to higher light intensities did not show a significant increase in transpiration, suggesting a potential trade-off between energy expenditure on supplemental lighting and dehumidification. This finding opens the possibility of reducing energy consumption for dehumidification and achieving economic savings by subjecting plants to optimal growing conditions for shorter durations. This depends on whether higher savings on dehumidification are achieved compared to the energy required to maintain high PPFD levels.

Nocturnal LED Supplemental Lighting Improves Quality of Tomato Seedlings by Increasing Biomass Accumulation in a Controlled Environment

Tomato (Solanum lycopersicum L. cv. Zhongza NO. 9) was used as the experimental material to investigate the effects of nocturnal LED supplemental light with the photosynthetic photon flux density (PPFD) of 100, 200, 300 μmol·m−2·s−1, and the light time of 1, 2 h on the seedling quality in a controlled environment, with seedlings without nocturnal supplemental lighting serving as the control. The results demonstrate that an increase in PPFD at night progressively enhances the plant height and leaf number of tomato seedlings, while stem diameter and leaf area initially increase and subsequently decrease. Although light time and light period-of-time at night did not significantly affect seedling morphology, PPFD and light time notably influenced chlorophyll content and net photosynthetic rate. An optimal lighting energy amount at night augmented photosynthetic capacity. However, excessive PPFD induced photoinhibition in the leaves. Additionally, appropriate nocturnal LED supplemental lighting significantly improved the antioxidant capacity of the seedlings, increased proline content, reduced malondialdehyde content, and bolstered the self-protection mechanisms of the seedlings against nocturnal light stress. Both the PPFD and light time at night promoted biomass accumulation in tomato seedlings. Specifically, when supplemental lighting was applied for 2 h at an intensity of 200 μmol·m−2·s−1, both the fresh and dry weights of the shoot and root significantly increased, and the seedling health index was highest. Therefore, appropriate nocturnal LED supplemental lighting positively impacts the health index and photosynthate accumulation of tomato seedlings, but controlling PPFD is essential to avoid photoinhibition.

Effect of the Addition of an Ultraviolet B Light Bulb for 6 Months to the Enclosure of Client-Owned Cockatiels (Nymphicus hollandicus) on Serum 25-Hydroxyvitamin D Concentrations

BackgroundThe objective of this study was to determine the effects of ultraviolet B (UVB) radiation on the serum concentration of 25-hydroxyvitamin D [25(OH)D] in pet cockatiels (Nymphicus hollandicus) living in their home environments. MethodsThirty client-owned cockatiels were allocated to an intervention group, consisting of exposure to a commercial coil fluorescent bulb, or a control group, with no exposure to supplemental lighting. Blood samples were collected at baseline (Day 0) and 6 months after simple randomization for measurement of 25(OH)D (Day 180). A linear mixed model was used to determine if serum 25(OH)D concentrations were influenced by time, group, age, or sex. ResultsAt baseline, median 25(OH)D concentration for the whole study population was 13nmol/L (range, 0.0-15.0nmol/L). At the end of the study, median 25(OH)D concentration for the whole study population was 6.5 nmol/L (0.0-15.0nmol/L), for the UVB group was 3 nmol/L (0.0-8.0nmol/L) and for the control group was 7.5nmol/L (6.0-11.0nmol/L). There was a statistically significant 50% reduction in 25(OH)D concentrations from the baseline to the final sampling period for the overall population, but no differences by group, age, or sex. Conclusion and clinical relevanceThe addition of a UVB bulb for 6 months to the enclosures of cockatiels did not increase their serum 25(OH)D concentrations. There was an unexplained decrease in both groups when comparing Day 0 to the Day 180 sampling period. The 50% attenuation in the UVB lighting group, although not statistically significant, may be clinically relevant and deserves further investigation.