Search Results (12)

Lighting from light-emitting diodes (LEDs) is one of the largest capital and operational expenses for indoor farms. While broad-waveband white LEDs are relatively inexpensive, their efficacy is lower than most narrow-band LEDs. This study aimed to determine how supplementing warm-white light with additional blue (400–499 nm), green (500–599 nm), red (600–699 nm), or far-red (700–750 nm) light influences lettuce (Lactuca sativa) growth and quality, and whether these effects are consistent across two photon flux densities (PFDs). We grew lettuce ‘Rouxai’ and ‘Rex’ under 90 or 180 µmol∙m⁻²∙s⁻¹ of warm-white light supplemented with 40 or 80 µmol∙m⁻²∙s⁻¹ of blue, green, red, far-red, or warm-white light. Supplemental far-red light increased biomass without reducing secondary metabolites. Supplemental red, far-red, and warm-white light maximized biomass, whereas additional blue light enhanced secondary metabolite concentrations and leaf coloration. Increasing the PFD increased biomass and phenolic content in ‘Rouxai’. Notably, spectral effects were consistent across PFD levels, suggesting that higher PFDs do not diminish spectral responses. These results demonstrate the potential of enriching white light to increase yield or quality in controlled-environment agriculture and provide insights for cost-effective commercial production. Full article

Canopy architecture is fundamental to productivity in grapevines. This research focused on evaluating the impact of opening canopies on the capture of photosynthetically active radiation, photosynthetic activity, and berries’ physicochemical properties in Cabernet Sauvignon grapevines. A completely randomised design was used to compare open and closed canopies, with ten replicates per treatment (20 vines in total), during the vegetative growth period and after harvest. The key measurements included photon flux density (PFD), daily light integral (DLI), photosynthetic rate (PR), stomatal conductance (SC), intercellular CO₂ concentration (IC), leaf area (LA), transpiration, ambient CO₂ concentration, and temperature. Additionally, we assessed berry quality variables, such as total soluble solids (TSS), glucose/fructose ratio, total titratable acidity (TTA), pH, TSS/TTA, and total phenols (TP). During vegetative growth, PFD, DLI, PR, IC, and LA increased significantly (p ≤ 0.05), whereas after harvest, only PR and IC showed variation Closed canopies increased water use efficiency (CO₂/H₂O) by 62.5%, while the temperature was higher in open canopies. Opening canopy increased contacts, gaps and visible sky and reduced leaf area index. Berries from open canopies showed higher TSS, glucose-fructose, pH, TSS/TTA and TP contents. Opening canopy is essential for improving light interception, photosynthetic efficiency, and fruit quality in Cabernet Sauvignon grapevine cultivated in northern Mexico. Full article

A tunable LED panel with multiple types of LEDs on a panel can provide various spectra for optimal plant growth. However, it is difficult for a lighting panel with multiple types of high-power LEDs to achieve uniform lighting. We demonstrated that by using optical reflectors at the sides of an LED panel to trap photons of LED arrays or using both the above-mentioned reflectors and optical lenses on each LED, high lighting uniformity can be achieved at a short distance to plants. The ray tracing simulation results show that the LED panel equipped with reflectors and optical lenses can achieve a high uniformity of >0.80 when the LED-plant distance is at half of the LED array’s pitch. We further verified that an LED panel (at a size of 88 cm × 54 cm) installed with reflectors can achieve light uniformities around 0.90 at a 15 cm LED-plant distance for the 6 types of LEDs (4 color LEDs and 2 white LEDs) on the panel. Compared with a branded tunable LED panel, our LED panel saves >25 cm vertical distance for each tier of plants and has 92.5% higher photon efficacy for 660 nm LEDs that exist on both panels. Full article

The present study has been carried out to determine the effects of four different illuminators with red, far-red, blue, and white light-emitting diodes (LEDs) on the growth, morphology, pigment composition, and chlorophyll fluorescence of spinach (Spinacia oleracea L.) of the ‘Zhirnolistny’ cultivar. We investigated these variants in two photon flux densities, 400–800 nm (PFD) 120 µmol m⁻² s⁻¹ and 180 µmol m⁻² s⁻¹. The studies were carried out in a climate chamber. Plant measurements were carried out on the 30th and 45th days of cultivation. The results showed that during the period of active growth, on the 30th day, spinach plants accumulated 2.6 and 2.4 times more fresh weight in the variant with a higher PFD (180 µmol m⁻² s⁻¹). At the end of the growing season, only a decrease in PFD had an effect on the fresh and dry weight of plants. The highest concentration of chlorophyll on both the 30th and 45th days of vegetation was found when spinach plants were grown under red-blue (RB) LEDs in a spectrum proportion of R70:B30. It was found that the variants had a higher proportion of green radiation in the spectrum of illuminators with PFD 180 µmol m⁻² s⁻¹, and the nitrate content in spinach was slightly lower than in other variants. Full article

Investigation is devoted to the optimization of light spectrum and intensity used for red mustard growing. Notably, most of the studies devoted to red mustard growing were conducted on micro-greens, which is not enough for the development of methods and recommendations for making the right choices about the irradiation parameters for full-cycle cultivation. In this study, we tested four models of LED with different ratios of blue, green red and far red radiation intensity: 12:20:63:5; 15:30:49:6; 30:1:68:1, in two values of photon flux density (PFD)—120 and 180 µmol m⁻² s⁻¹—to determine the most effective combination for red mustard growing. The study was conducted in a container-type climate chamber, where the red leaf mustard was cultivated in hydroponics. On the 30th day of cultivation, the plant’s morphological, biochemical and chlorophyll fluorescence parameters, and reflection coefficients were recorded. The results indicated that the PFD 120 µmol m⁻² s⁻¹ had a worse effect on both mustard leaf biomass accumulation and nitrate concentration (13–30% higher) in the plants. The best lighting option for growing red mustard was the blue–red spectrum, as the most efficient in terms of converting electricity into biomass (77 Wth/g). This light spectrum contributes to plant development with a larger leaf area (60%) and a fresh mass (54%) compared with the control, which has a maximum similarity in spectrum percentage to the sunlight spectrum. The presence of green and far red radiation with the blue–red light spectrum in various proportions at the same level of PFD had a negative effect on plant fresh mass, leaf surface area and photosynthetic activity. The obtained results could be useful for lighting parameters’ optimization when growing red mustard in urban farms. Full article

Indoor crop cultivation systems such as vertical farms or plant factories necessitate artificial lighting. Light spectral quality can affect plant growth and metabolism and, consequently, the amount of biomass produced and the value of the produce. Conflicting results on the effects of the light spectrum in different plant species and cultivars make it critical to implement a singular lighting solution. In this study we investigated the response of cyanic and acyanic lettuce cultivars to an increased proportion of blue light. For that, we selected a green and a red leaf lettuce cultivar (i.e., ‘Aquino’, CVg, and ‘Barlach’, CVr, respectively). The response of both cultivars to long-term blue-enriched light application compared to a white spectrum was analyzed. Plants were grown for 30 days in a growth chamber with optimal environmental conditions (temperature: 20 °C, relative humidity: 60%, ambient CO₂, photon flux density (PFD) of 260 µmol m⁻² s⁻¹ over an 18 h photoperiod). At 15 days after sowing (DAS), white spectrum LEDs (WW) were compared to blue-enriched light (WB; λ_Peak = 423 nm) maintaining the same PFD of 260 µmol m⁻² s⁻¹. At 30 DAS, both lettuce cultivars adapted to the blue light variant, though the adaptive response was specific to the variety. The rosette weight, light use efficiency, and maximum operating efficiency of PSII photochemistry in the light, F_v/F_m’, were comparable between the two light treatments. A significant light quality effect was detected on stomatal density and conductance (20% and 17% increase under WB, respectively, in CVg) and on the modified anthocyanin reflectance index (mARI) (40% increase under WB, in CVr). Net photosynthesis response was generally stronger in CVg compared to CVr; e.g., net photosynthetic rate, P_n, at 1000 µmol m⁻² s⁻¹ PPFD increased from WW to WB by 23% in CVg, compared to 18% in CVr. The results obtained suggest the occurrence of distinct physiological adaptive strategies in green and red pigmented lettuce cultivars to adapt to the higher proportion of blue light environment. Full article

The study aimed to evaluate the effect of different photon flux density (PFD) and light-emitting diodes (LED) wavelengths on strawberry Colletotrichum acutatum growth characteristics. The C. acutatum growth characteristics under the blue 450 nm (B), green 530 nm (G), red 660 nm (R), far-red 735 nm (FR), and white 5700 K (W) LEDs at PFD 50, 100 and 200 μmol m⁻² s⁻¹ were evaluated. The effect on C. acutatum mycelial growth evaluated by daily measuring until five days after inoculation (DAI). The presence of conidia and size (width and length) evaluated after 5 DAI. The results showed that the highest inhibition of fungus growth was achieved after 1 DAI under B and G at 50 μmol m⁻² s⁻¹ PFD. Additionally, after 1–4 DAI under B at 200 μmol m⁻² s⁻¹ PFD. The lowest conidia width was under FR at 50 μmol m⁻² s⁻¹ PFD and length under FR at 100 μmol m⁻² s⁻¹ PFD. Various LED light wavelengths influenced differences in C. acutatum colonies color. In conclusion, different photosynthetic photon flux densities and wavelengths influence C. acutatum growth characteristics. The changes in C. acutatum morphological and phenotypical characteristics could be related to its ability to spread and infect plant tissues. This study’s findings could potentially help to manage C. acutatum by LEDs in controlled environment conditions. Full article

This study was conducted to compare the effects of broad spectrum during the whole seedling period and photon flux density (PFD) in the healing stage on the growth and energy use efficiency of grafted tomato (Lycopersicon esculentum Mill.) transplants in a plant factory. Fluorescent lights, white LED lights, and white plus red LED lights were applied at the growth processes of grafted tomato transplants from germination of rootstock and scion to post-grafting. Three levels of PFD (50, 100, 150 μmol m⁻² s⁻¹) were set in the healing stage under each kind of light quality. The results indicated that the growth and quality of grafted tomato transplants under different broad spectrums were influenced by the ratio of red to blue light (R/B ratio) and the ratio of red to far-red light (R/FR ratio). A higher R/B ratio was beneficial to total dry matter accumulation, but excessive red light had a negative effect on the root to shoot ratio and the seedling quality index. The higher blue light and R/FR ratio suppressed stem extension synergistically. The LED lights had good abilities to promote plant compactness and leaf thickness in comparison with fluorescent lights. The plant compactness and leaf thickness increased with the increase in daily light integral in the healing stage within a range from 2.5 to 7.5 mol m⁻² d⁻¹ (PFD, 50 to 150 μmol m⁻² s⁻¹). Compared to fluorescent lights, the LED lights showed more than 110% electrical energy saving for lighting during the whole seedling period. Higher PFD in the healing stage did not significantly increase the consumption of electric power for lighting. White plus red LED lights with an R/B ratio of 1.2 and R/FR ratio of 16 were suggested to replace fluorescent lights for grafted tomato transplants production considering the high quality of transplants and electrical energy saving, and PFD in the healing stage was recommended to be set to 150 μmol m⁻² s⁻¹. Full article

Selenium (Se) is an essential microelement for human health and has antioxidant and anticancerous properties. One of the ways to increase its concentration in plants is biofortification through various agronomic practices including artificial lighting. The aim of this study was to determine the responses of baby leaf lettuce to various Se content in hydroponic solution at different ratios of blue (B) and red (R) light of light-emitting diodes (LED) lighting. Lettuce (Lactuca sativa, ‘Little Gem’) was grown hydroponically under B:R light ratios–10%B:90%R, 75%B:25%R. The photon flux density (PFD), photoperiod, temperature, and relative humidity in the growth chamber were maintained at 220 μmol m⁻² s⁻¹, 18 h, 21/17 ± 2 °C, and 60 ± 5%, respectively. Two experiments with Se were performed using natrium selenate (Na₂SeO₄). Results of the first experiment (Se–0, 1, 3 ppm) showed that the content of Se in lettuce was about 15 times higher at 3 ppm compared to 1 ppm. Similar trends were observed for both B and R ratios. However, even the lowest dose of Se in hydroponic solution inhibited lettuce growth and reduced photosynthesis and chlorophyll content. Therefore, a second experiment was performed with lower Se doses (0, 0.5, 1 ppm) at different growth stages (11th and 17th days after sowing (DAS)). It was found that, when Se exposure was initiated at the 17th DAS, the lettuce accumulated a lower content of Se compared to the 11th DAS, but this did not have a negative effect on their growth. The B:R ratio of 10B:90R% resulted in a higher content of Se in the leaves. Overall, these results suggest that properly composed doses of Se, LED lighting and application time could be a suitable way for cultivation of selenium-biofortified baby leaf lettuces without any adverse effects on growth. Full article

Blue light and ultra-violet (UV) light have been shown to influence plant growth, morphology, and quality. In this study, we investigated the effects of pre-harvest supplemental lighting using UV-A and blue (UV-A/Blue) light and red and blue (RB) light on growth and nutritional quality of lettuce grown hydroponically in two greenhouse experiments. The RB spectrum was applied pre-harvest for two days or nights, while the UV-A/Blue spectrum was applied pre-harvest for two or four days or nights. All pre-harvest supplemental lighting treatments had a same duration of 12 h with a photon flux density (PFD) of 171 μmol m⁻² s⁻¹. Results of both experiments showed that pre-harvest supplemental lighting using UV A/Blue or RB light can increase the growth and nutritional quality of lettuce grown hydroponically. The enhancement of lettuce growth and nutritional quality by the pre-harvest supplemental lighting was more effective under low daily light integral (DLI) compared to a high DLI and tended to be more effective when applied during the night, regardless of spectrum. Full article

The photon flux density (PFD) and spectrum regulate the growth, quality attributes, and postharvest physiology of leafy vegetables grown indoors. However, limited information is available on how a photon spectrum enriched with a broad range of different wavebands regulates these factors. To determine this, we grew baby-leaf lettuce ‘Rouxai’ under a PFD of 200 µmol m⁻² s⁻¹ provided by warm-white (WW; control) light-emitting diodes (LEDs) supplemented with either 30 µmol m⁻² s⁻¹ of ultraviolet-A (+UV30) or 50 µmol m⁻² s⁻¹ of blue (+B50), green (+G50), red (+R50), or WW (+WW50) light. We then quantified growth attributes and accumulated secondary metabolites at harvest and during storage in darkness at 5 °C. Additional +G50 light increased shoot fresh and dry weight by 53% and 59% compared to the control. Relative chlorophyll concentration increased under +UV30, +G50, and especially +B50. At harvest, +B50 increased total phenolic content (TPC) by 25% and anthocyanin content (TAC) by 2.0-fold. Additionally, +G50 increased antiradical activity (DPPH) by 29%. After each day of storage, TPC decreased by 2.9 to 7.1% and DPPH by 3.0 to 6.2%, while TAC degradation was less pronounced. Principal component analysis indicated a distinct effect of +G50 on the lettuce at harvest. However, concentrations of metabolites before and during storage were usually greatest under the +B50 and +R50 treatments. Full article

The use of Light Emitting Diode (LED) lights in microscale vegetable production is more and more widespread. In this context, the effect of light spectrum on photosynthesis, growth, shoot yield, pigment content, and nutritional status of einkorn seedlings (Triticum monococcum L. ssp. monococcum), germinated and grown in a nutrient solution, was investigated. Plants were subjected to six different LED light treatments, all having a photon flux density (PFD) of 200 μmol m⁻² s⁻¹. Two light treatments were monochromatic (red or blue), three dichromatic (blue and red in the proportion), and one of a wider spectrum (selected as a control). All the light treatments affected the morphological, biochemical, and nutritional status of einkorn seedlings. Overall, the dichromatic treatments were the most effective in stimulating biomass production, CO₂ assimilation, and evapotranspiration, as well as contents in chlorophyll a and b and carotenoids, and additionally nitrogen, phosphorous, manganese, iron, and zinc. These results are of relevance for the beneficial effects of dichromatic LED treatments in maximizing einkorn shoot yield and nutritional values, and in limiting energy consumption in indoor cultivation. Full article