Search Results (1,663)

This study evaluated the effects of different LED spectral irradiance ratios on the growth, secondary metabolites, and essential oil characteristics of Ocimum × africanum Lour. cultivated for four weeks under controlled conditions. Four LED lighting treatments with different red, blue, green, ultraviolet-A, and far-red light ratios, and a treatment in greenhouse as low-light control were used. The constant 16 h photoperiod and light intensity of 220 µmol·m⁻²·s⁻¹ were maintained. The F2 treatment (UV-A:B:R:Fr = 6.60:45.15:29.23:19.02) promoted the greatest plant height (76.62 cm), and chlorophyll a (7.41 mg/100 g, FW), chlorophyll b (4.73 mg/100 g, FW), and total phenolic (25.78 mg/g, FW) concentrations. F1 treatment (B:G:R:Fr = 17.14:29.8:47.4:5.66) produced significantly higher (p < 0.01) biomass (8.3 ton/ha, FW), oil yield (10.89 L/ha), and carotenoid (3.74 mg/100 g, FW) than the others. Essential oils contained 12–15 compounds, dominated by neral (27.5–37.3%), geranial (41.1–49.9%), and (E)-β-caryophyllene (2.4–9.9%), while the highest contents of oil (0.83%, DW), anthocyanin (16.50 mg/100 g, FW), and total flavonoid (14.17 mg/g, FW) were obtained under F4 (B:G:R:Fr = 13.85:43.50:39.30:3.35). These findings demonstrate that optimized LED spectra can effectively improve both productivity and phytochemical quality in O. africanum through regulating both primary and secondary metabolism. Full article

White LEDs are widely used in fields such as lighting and display. However, existing white light devices suffer from excessively broad emission spectra full width at half maximum (FWHM) and severe leakage of pump blue light. Hence, this study proposes a theoretical design for an ultra-narrow-band white LEDs based on an asymmetric Fabry-Pérot (F-P) microcavity. The microcavity employs a dual-DBR configuration with asymmetric optical responses: the bottom DBRs utilize a ZnS/MgF₂ ($d_L$/2-$d_H$-$d_L$/2)⁵ stack, providing a low reflectance of ~20% at 457 nm for efficient blue light transmission and quantum dot excitation; conversely, the final device incorporating top DBRs with a TiO₂/MgF₂ ($d_H$/2-$d_L$-$d_H$/2)⁴-stacked structure achieved a high reflectivity of approximately 89% at 457 nm, effectively decreasing the excessive blue light in the output spectrum. The intermediate emissive layer uses polymethyl methacrylate (PMMA) as the quantum dot host. By precisely tuning the cavity thickness, the resonant modes of the F-P microcavity—specifically the fourth-order (626 nm) and fifth-order (534 nm)—are aligned with the emission peaks of the red and green quantum dots, respectively. Simulation results demonstrate that the structure leverages the cavity filtering effect to compress the FWHM of the red and green emissions from initial values of 36.5 nm and 29.8 nm down to 2.2 nm and 1.9 nm, respectively, representing an order-of-magnitude improvement in color purity. Through the co-optimization of the top-DBR’s central wavelength, cavity optical thickness, and the doping ratio of red/green quantum dots, standard white light emission with CIE coordinates of (0.32, 0.33) was achieved, accompanied by emission efficiencies of 6.3% (green) and 22.3% (red) for the QDs. However, strict manufacturing tolerances and narrow observation angles limit the applicability of the device. This work provides theoretical research for developing white light sources. Full article

Surface quality is a critical indicator of product performance, creating a growing demand for real-time surface inspection in industrial manufacturing. However, conventional surface normal measurement techniques require sequential measurements with varying illumination or observation angles, making them unsuitable for high-speed online inspection. To overcome this limitation, this paper proposes a novel imaging technique, termed normalography, for visualizing pixel-wise surface normal distributions. Analogous to thermography, normalography visualizes the spatial distribution of surface normal directions over a material surface. The proposed method targets highly glossy and smooth surfaces and is based on reflectance measurements. A multi-angle collimator was developed to simultaneously illuminate the target surface from multiple incident directions, while multispectral illumination was employed to distinguish the reflected light corresponding to each direction. An imaging system incorporating red, green, and blue illumination sources enables single-shot acquisition of surface normal information over a 1024 × 1024-pixel field of view. The proposed normalography enables camera-like real-time visualization of surface normal distributions without sequential image acquisition, demonstrating its potential for online surface inspection and quality monitoring in industrial manufacturing. Full article

This study evaluated LED-supported speed-breeding conditions for two registered soybean cultivars (‘Sonya’ and ‘Victoria’; approximately Maturity Groups III–IV) by testing four constant photoperiod regimes (10, 14, 18, and 22 h light) combined with four LED spectral treatments differing in high red (HR; 640–660 nm), deep blue (DB; 450–460 nm), far-red (FR; 720–730 nm), cool white (CW; 6500 K; 400–700 nm) and warm white (WW; 3000 K; 400–700 nm) components. Photoperiod treatments were implemented as sequential runs in a controlled growth-chamber (28 ± 2 °C; ≥50% RH; 400–600 µmol·m⁻²·s⁻¹ PPFD), and performance was compared with a field trial in Antalya, Türkiye. Developmental timing (R1, R6), plant height, stem dry weight, pod number, seed oil concentration, fatty acid composition, and seed germination were analyzed using mixed-effects and generalized linear mixed models. Photoperiod exerted dominant control over developmental timing. The 10 h photoperiod regime produced the fastest progression (R1 ≈ 24.5 DAS; R6 ≈ 50 DAS), whereas 18 h markedly delayed R1 and R6 (with one LED treatment within 18 h failing to reach R6), and 22 h did not reach R6. LED spectral treatment did not affect R1 or R6 within photoperiods, but influenced plant height, stem dry weight, total seed oil, and germination. Field-grown plants produced substantially higher biomass and pod number than growth chamber-grown plants, consistent with greater branching and pod set under open-field, direct-sown conditions. Total seed oil concentration differed by environment and cultivar with no environment × cultivar interaction, while centered log-ratio PERMANOVA indicated largely stable fatty acid proportional composition across environments and LED treatments. Germination analyses (restricted to 10 h and 14 h due to insufficient seed production) showed significant effects of LED treatment and harvest timing, with the highest germination under LED–3. Overall, our results indicate that a constant 10 h photoperiod, combined with immature seed harvest from approximately R6 + 20 onward, provides an effective strategy for accelerating soybean generation turnover while maintaining high germination capacity. LED spectral design can also be used to modulate plant architecture and seed quality without substantially altering developmental timing. Full article

Light quality plays a critical role in regulating plant growth during both in vitro culture and hydroponic stages, attracting increasing research attention. However, comprehensive studies incorporating far-red LED light throughout the entire growth cycle of Spathiphyllum floribundum (Linden & André) N.E.Br. ‘Tianjiao’ remain limited. To investigate the effects of red, blue, and far-red light ratios on proliferation, rooting, and hydroponic acclimatization, six LED treatments were established with red: blue ratios of 80:20, 70:30, and 60:40, each with or without far-red light supplementation. Fluorescent light was used as the control. At each stage, morphological traits, photosynthetic pigments, osmotic compounds, antioxidant enzyme activities, and photosynthetic parameters were measured. The results identified distinct optimal light combinations for each growth phase. The optimal treatment for proliferation was 80%R + 20%B + Fr, which produced significant proliferation coefficients and enhanced chlorophyll b and soluble protein content. For rooting, 60%R + 40%B + Fr was most effective, resulting in the highest total chlorophyll content (0.109 mg·g⁻¹) and improved carotenoid accumulation and CAT activity. During hydroponic acclimatization, 60%R + 40%B without far-red light yielded the best performance, achieving the highest plant height (15.28 cm) and net photosynthetic rate (4.77 μmol·m⁻²·s⁻¹), along with improved water-use efficiency. These results provide potential LED light strategies for the complete process from tissue culture to hydroponics, offering a theoretical basis for designing specialized LED lighting systems for plant tissue culture and hydroponic production. Full article

Phosphorus (Pi) deficiency limits plant productivity. Light quality modulates growth and stress responses, but its interaction with Pi starvation in banana is unclear. We investigated physiological, transcriptomic, and metabolomic responses of banana seedlings to low Pi under white (WL), red (R), far-red (FR), blue (B), and ultraviolet (UV-A) light. FR light promoted shoot elongation and increased phosphorus, iron, and calcium accumulation, whereas B and UV-A exacerbated growth inhibition and oxidative stress (higher H₂O₂, MDA, and proline). Transcriptomics revealed that B and UV-A enriched cell cycle and stress pathways, while FR enriched photosynthesis and cell wall biogenesis. Expression of phosphate transporters and starvation-responsive genes was spectrum-specific. Metabolomics showed B and UV-A triggered massive accumulation of ABA, flavonoids, and secondary metabolites, indicating strong stress defense. Antioxidant enzyme activities were differentially activated: B upregulated SOD, CAT, and POD; UV specifically enhanced GSH-Px. Integrated correlation networks revealed distinct regulatory hubs: blue light centered on ROS scavenging, red light on phosphate transport. Our findings demonstrate that FR light acts as a positive regulator, while B and UV-A act as additional stressors under Pi deficiency, providing a mechanistic framework for using light spectra to improve crop resilience in Pi-limited conditions. Full article

Fruit color is a key quality trait in cherry tomato (Solanum lycopersicum) and an important factor influencing consumer purchasing decisions. Various pigments, including flavonoids, carotenoids, and chlorophylls, form the biochemical basis of fruit coloration, imparting vivid colors such as red, yellow, orange, and green. Flavonoids and carotenoids are also essential nutritional components in cherry tomato, directly influencing their commercial value, while chlorophylls are crucial for photosynthesis and fruit development. However, conventional tomato varieties typically contain insufficient flavonoid levels to meet human dietary requirements. In this study, we quantified flavonoids, carotenoids, and chlorophyll a and b in ten high-flavonoid cherry tomato cultivars and investigated the relationships between fruit color and pigment content. The results revealed that red and orange tomato varieties contained higher flavonoid and carotenoid levels than yellow varieties, while green tomatoes exhibited elevated chlorophyll content. Yellow varieties showed the maximum L* (lightness) value. Flavonoid and carotenoid contents were significantly positively correlated with a* (red-green axis) and a*/b* (yellow-blue axis) values but negatively correlated with hue angle, whereas chlorophyll content showed no significant correlations with color parameters. Our findings provide guidance for evaluating the nutritional value of cherry tomatoes based on pigmentation. Full article

Chickpea (Cicer arietinum L.) is a highly nutritious legume with significant potential as a food plant. With the advent of climate change and the challenge of feeding a growing population, strategies to produce high-nutrient crops are of utmost importance. In this context, this study describes how light intensity and wavelength affect the embryonic axis of chickpea sprout metabolism, using untargeted metabolomics. Chickpea sprouts were grown under varying light wavelengths (red—650, green—550, and blue—450 nm) at two intensities (75 and 275 µmol·m⁻²·s⁻¹). Analyses were restricted to the embryonic axis (hypocotyl), excluding the cotyledons, which are a reserve-rich tissue. Results showed that high-intensity red light (RH) increased phenolic content by more than 300% compared to controls. Green and blue light treatments significantly increased the protein content by more than twice that of the dark control. Antioxidant activity was significantly higher in sprouts grown under high-intensity blue light (BH). Additionally, the results suggested that pathway regulation is affected not only by wavelength but also by light intensity, with greater significance and effect under BH and RH treatments in isoflavonoid biosynthesis. High quercetin concentration found under BH is hypothesized to explain the high antioxidant activity when compared to the rest. For instance, these findings highlight the potential of light manipulation to modulate and enhance the nutritional and functional qualities of chickpea sprouts’ embryonic axis, contributing to food security and human health. Further studies need to be conducted to answer whether these metabolite changes directly translate to the nutritional quality of the whole edible sprouts. Full article

This study aimed to investigate the effects of different light-emitting diode (LED) light-quality combinations on the growth and development of Chrysanthemum morifolium tissue-cultured plantlets and to identify the optimal light-quality combinations for adventitious shoot induction and rooting. Six LED light-quality combinations consisting of red (R), blue (B), and far-red (Fr) light (80%R + 20%B, 70%R + 30%B, 60%R + 40%B, 80%R + 20%B + Fr, 70%R + 30%B + Fr, and 60%R + 40%B + Fr) were evaluated, with a fluorescent lamp serving as the control (CK). The responses to different light-quality combinations varied markedly between the adventitious shoot induction and rooting stages. During adventitious shoot induction, the carotenoid content, soluble protein content, and POD activity were highest under the 70%R + 30%B treatment, whereas chlorophyll a, chlorophyll b, total chlorophyll, and CAT activity reached their highest levels under the 70%R + 30%B + Fr treatment. The highest soluble sugar content and SOD activity were observed under the 60%R + 40%B + Fr treatment. These results suggest that the incorporation of far-red light into red–blue light combinations promoted photosynthetic pigment synthesis, photosynthate accumulation, and antioxidant capacity, thereby facilitating adventitious shoot induction. During the rooting stage, the greatest leaf number and SOD activity were observed under the 70%R + 30%B treatment, while the highest chlorophyll a, chlorophyll b, and total chlorophyll contents were obtained under the 60%R + 40%B + Fr treatment. Plant height, leaf length, root length, fresh mass, dry mass, carotenoid content, soluble protein content, and CAT activity were highest under the 60%R + 40%B treatment. These findings indicate that red–blue mixed light effectively promoted leaf and root development, photosynthetic pigment synthesis, biomass accumulation, and maintenance of antioxidant capacity. Therefore, the 70%R + 30%B + Fr and 60%R + 40%B + Fr treatments were identified as the most suitable light-quality combinations for adventitious shoot induction, whereas the 60%R + 40%B treatment was the most suitable for rooting of C. morifolium tissue-cultured plantlets. Full article

Modern optoelectronic devices, such as light-emitting diodes (LEDs) and laser diodes, rely on nitride-based (GaN, AlN, and InN) quantum structures, which underpin current technologies. These systems enable emission across a broad spectral range from ultraviolet to infrared with properties tunable via composition, strain, and quantum confinement. This review summarizes progress in the performance of nitride emitters across the full spectral range, with particular emphasis on the evolution of external quantum efficiency (EQE). Nitride emitters are primarily based on InGaN quantum wells, while AlGaN quantum wells are used for ultraviolet operation. Device performance is governed by the intrinsic properties of these structures, which also determine key physical challenges across different wavelength regions. Blue InGaN LEDs achieve the highest efficiencies (~60–80% EQE), while green devices are limited to ~20–35% due to the “green gap,” with further reduction (~5–20%) toward longer wavelengths. In the ultraviolet, AlGaN-based emitters exhibit lower performance due to material and structural challenges, although steady progress is being made. Special attention is given to mechanisms limiting EQE, including efficiency droop in the green–red region, and ongoing efforts to mitigate these effects. Finally, perspectives for future applications of [ are outlined. Full article

The proliferation of light-emitting diodes (LEDs) in urban and agricultural settings has intensified artificial light at night (ALAN), yet the molecular mechanisms underlying its spectrally specific perturbation of insect physiology remain elusive. We used high-throughput RNA sequencing to dissect the transcriptomic responses of Diaphorina citri—a principal vector of citrus Huanglongbing—to nocturnal exposure to monochromatic LED emissions at 460 nm (blue), 520 nm (green), 570 nm (yellow), and 620 nm (red). Blue light triggered metabolic reprogramming coupled with stress responses. Red light predominantly engaged lysosomal–autophagic pathways and lipid metabolism. Yellow and green light produced only modest transcriptional alterations with no significant pathway enrichment. These results demonstrate that D. citri exhibits a markedly wavelength-dependent transcriptomic response to nocturnal monochromatic illumination, with short-wavelength blue and long-wavelength red light eliciting pronounced physiological effects through distinct molecular routes, thereby providing mechanistic insight into wavelength-specific ALAN impacts and a rationale for targeted optical pest management strategies. Full article

Seed vigor directly affects emergence rate, early emergence capacity, and seedling uniformity in ginseng. This study integrated pre-sowing laser treatment with hyperspectral prediction for rapid evaluation of ginseng seed vigor. Cracked-stage Mountain Cultivated Ginseng Seeds and American Ginseng Seeds were treated with four semiconductor laser conditions, including red light, blue light, red–blue 3:1, and red–blue 6:1, for 5, 15, and 30 min. Emergence rate, emergence energy, and emergence index were evaluated, and 350–2500 nm hyperspectral reflectance data were collected. Different preprocessing, feature selection, and machine learning methods were compared to construct an optimized support vector regression model for emergence rate prediction. The results showed that laser effects were seed-type-specific and parameter-dependent. Mountain Cultivated Ginseng Seeds responded strongly, with 5 min blue light treatment producing the best performance, achieving a 100.0% emergence rate, 40.4 percentage points higher than the control, with significantly higher emergence energy and emergence index. In American Ginseng Seeds, no treatment differed significantly from the control, although the 30 min red light treatment showed the highest emergence rate trend. Savitzky–Golay smoothing combined with the second derivative was the optimal preprocessing method. The Caterpillar Fungus Optimizer-based support vector regression (CFO-SVR) joint optimization model achieved the best prediction performance, with ${\mathrm{R}}_{\mathrm{p}}^2$ of 0.9517, ${\mathrm{R}\mathrm{M}\mathrm{S}\mathrm{E}}_{\mathrm{P}}$ of 2.4766, and ${\mathrm{M}\mathrm{A}\mathrm{E}}_{\mathrm{P}}$ of 1.0730. These results provide a feasible technical reference for pre-sowing treatment of ginseng seeds and rapid, non-destructive evaluation of emergence vigor. Full article

Mustard (Brassica juncea) sprouts are appreciated for their high levels of bioactive constituents, but how light quality and exogenous selenium interactively regulate their growth and nutritional properties is still poorly understood. In this study, we evaluated the individual and combined effects of red (R), white (W) and blue (B) light together with 100 μmol·L⁻¹ selenium solution (SeR, SeW, SeB) on sprouts growth, health-promoting compounds, and metabolic profiles. Under single light quality treatments, red light favored growth, white light promoted photosynthetic pigment accumulation, and blue light most effectively enhanced antioxidant compounds and glucosinolates. Combined treatments further improved both yield and quality. SeR showed the greatest gains in growth indices; SeW achieved the highest total chlorophyll, total carotenoids, and total glucosinolates (the latter reaching 108.18 μmol g⁻¹ DW), and SeB attained the highest total selenium, soluble sugar, soluble protein, anthocyanins, ascorbic acid, flavonoids, total phenolics, and antioxidant capacity. Non-targeted metabolomics identified 1208 differential metabolites, with KEGG enrichment revealing that the phenylpropanoid biosynthesis pathway was significantly enriched across all selenium-treated groups. These findings demonstrate that targeted combinations of light quality and exogenous selenium can selectively enhance the growth or nutritional quality of mustard sprouts, offering practical guidance for their controlled-environment production. Full article

Junction temperature (T_j) is a key parameter that directly governs the optical performance and operational reliability of light-emitting diodes (LEDs), which have become indispensable in modern illumination and display systems. Accurate real-time T_j monitoring is critical for ensuring device longevity and consistent light output. Although the forward voltage method (FVM) remains the industry benchmark, its practical implementation is hindered by the need for costly high-speed switching modules and ultra-low-current calibration sources, restricting its deployment in real-time and cost-sensitive scenarios. To overcome these limitations, we introduce and experimentally validate a non-contact optical method for T_j determination that leverages the normalized integral width (NIW) of the LED emission spectrum as a temperature-sensitive spectral parameter. The underlying principle is that spectral broadening—arising from enhanced carrier thermal excitation and temperature-induced bandgap shrinkage—exhibits a robust and quantifiable linear correlation with T_j. Both theoretical analysis and experimental data confirm that this mechanism underpins the excellent linear correlation between NIW and T_j observed across a wide range of LED types, including monochromatic (red, green, blue) and phosphor-converted white LEDs. A rigorous theoretical analysis establishes the mathematical framework linking NIW to T_j. Experimentally, a measurement system centered on a modified commercial spectrometer was constructed. Extensive testing on a diverse array of power LEDs consistently demonstrates an excellent linear correlation (R² > 0.998) between NIW and T_j under normal drive conditions (e.g., typical operating currents). A comparative analysis against the benchmark FVM, conducted using a Mentor Graphics T3Ster system, demonstrates that the proposed method achieves comparable measurement accuracy, with a maximum deviation of merely 2.1 °C, while substantially reducing system cost and complexity. Validation across diverse LED types confirmed excellent linearity and high repeatability. A comparative analysis with established optical methods (e.g., peak wavelength, blue-white ratio, Raman thermography) further underscores the advantages of the NIW method in terms of cost-effectiveness, measurement speed, and broader applicability. Subsequent evaluation of critical factors, including self-heating, ambient light interference, and spectrometer resolution, demonstrates its robustness. Consequently, the NIW method presents a practical solution for real-time, non-intrusive thermal monitoring, well-suited for industrial LED production and quality control. Full article

Supplemental light spectrum strongly influences crop physiology, quality, and marketability in controlled-environment horticulture. This study evaluated greenhouse-grown basil (Ocimum basilicum L.) under natural daylight supplemented with 250 µmol m⁻² s⁻¹ of multi-band WHITE or narrow-band RED, GREEN, and BLUE LEDs, compared with non-supplemented controls (CNT). Diurnal gas exchange, cumulative photosynthetic activity, quality, sensory traits, and productive responses were assessed to identify spectrum-specific effects. WHITE supplementation produced the highest net photosynthesis (P_n) throughout the photoperiod, increasing carbon assimilation by up to 90% during active supplementation compared with CNT, while improving stomatal–photosynthetic coordination and titratable acidity. BLUE light promoted the highest stomatal conductance and transpiration, whereas RED induced faster stomatal closure without affecting the plant’s final biomass. GREEN supplementation showed intermediate physiological responses while enhancing fresh biomass, leaf brightness, and greenness. Spectral treatments significantly affected chlorophyll content, colorimetric parameters, sensory descriptors, aroma typicity, and texture, although antioxidant activity and overall consumer acceptability remained largely stable. WHITE and CNT samples achieved the highest sensory appreciation, while BLUE supplementation increased bitterness and reduced aromatic typicality. Overall, no single spectrum optimized all production objectives. WHITE provided the most balanced strategy for maximizing photosynthetic efficiency and premium-quality traits, whereas RED, GREEN, and BLUE offered more specialized benefits related to biomass increase, visual quality, or pigmentation. These findings highlight precision spectral management as an effective tool for tailoring basil production to specific agronomic and commercial targets in protected cultivation systems. Full article