Search Results (46)

In this study several phosphorus fertilizers were evaluated under controlled production conditions using Lactuca sativa var. baby leaf and a clay-loam soil of pH 6.5 as a plant–soil model system. Various inorganic (phosphate rock, monoammonium phosphate, struvite), organic (bone meal and bone meal pelletized with compost) and organomineral fertilizers (phosphate rock, monoammonium phosphate, struvite pelletized with compost) were compared. The soil properties, crop yield, morphological aspects and metabolomics of the plants were analyzed. After 45 days of the growing cycle, the organomineral fertilizers (OMFs) composed of compost and monoammonium phosphate (OMF₂(MAP+C)) or struvite (OMF₃(STR+C)) exhibited the best yield results: 101.37 g and 83.21 g, respectively. These treatments also exhibited the best phosphorus use efficiency (PUE) results: 7.40% and 8.33%, respectively. The yield of plants treated with MAP was 56.01 g, and its PUE was 5.33%. The yield of plants treated with STR was 62.10 g and the PUE was 4.67%. Accordingly, the development of OMFs with compost had a positive effect regarding MAP and STR fertilization. Lettuce fertilized with organic bone meal fertilizers had the lowest yield and nutrient use efficiency. The non-targeted metabolic study of green tissue revealed an overactivation of the TriCarboxylic Acids-TCA cycle and amino acid biosynthesis in plants fertilized with bone meal and phosphate rock treatments, likely as a plant stress response. The overall conclusion of this work is that the development of OMFs with compost is a good strategy to increase soil P availability and, accordingly, plant P uptake and %PUE. Full article

Vertical farming is gaining popularity as a sustainable solution to global food demand, particularly in urban areas where space is limited. However, optimizing key factors such as planting density remains a critical issue, as it directly affects light interception, energy efficiency, and crop yield. Lettuce and basil, the most commonly grown crops in vertical farms, were chosen for this study, with the aim of addressing the impact of planting density on light interception and overall productivity for improving the performance and sustainability of vertical farming systems. Plants were grown in an ebb-and-flow system of a fully controlled experimental vertical farm, where light was provided by light-emitting diode fixtures delivering a photoperiod of 16 h d⁻¹ and 200 µmol m⁻² s⁻¹ of photosynthetic photon flux density. Experimental treatments included three planting densities, namely 123 (low density, LD), 237 (medium density, MD), and 680 (high density, HD) plant m⁻². At the final harvest (29 days after sowing), the adoption of the highest planting density (680 plant m⁻²) resulted in greater fresh yield (kg FW m⁻²), leaf area index (LAI, m² m⁻²), light use efficiency (LUE, g DW mol⁻¹) and light energy use efficiency (L-EUE, g FW kWh⁻¹) for both lettuce (+207%, +227%, +142%, +206%, respectively), and basil (+312%, +316%, +291, +309%, respectively), as compared to the lowest density (123 plant m⁻²). However, the fresh and dry weights of the individual plants were lowered, probably as a result of the reduced light availability due to the highly dense plants’ canopy. Overall, these findings underscore the potential of increasing planting density in vertical farms to enhance yield and resource efficiency. Full article

The nutritional quality and biochemical properties of ‘Little Gem’ (Lactuca sativa L.) lettuce grown hydroponically can be enhanced by Zn and white light. This study investigated the combined effects of wide-spectrum white LED lighting parameters and Zn doses on the Zn accumulation, enzymatic and non-enzymatic antioxidants, sugars, and protein content of lettuce. Broad-spectrum 3500 K light combined with a 5 ppm Zn solution led to a 7% increase in Zn accumulation in lettuce, compared to 3000 K and 4000 K lighting conditions. The 5 ppm Zn dose combined with 3000 K and 4000 K lighting affected DPPH and ABTS scavenging activity and Fe-reducing antioxidant power. Additionally, this combination influenced chlorophyll b, maltose, superoxide dismutase, and ascorbate peroxidase levels. Furthermore, the 1 and 5 ppm Zn doses at 4000 K impacted carotenoids such as neoxanthin, lutein, zeaxanthin, and total protein content. In lettuce exposed to a 1 ppm Zn dose combined with 3000 K and 3500 K lighting, impact was found on total phenolic compounds, sucrose, chlorophyll a, raffinose, fructose, glucose, carotene, violaxanthin, and xanthophylls. The study suggests that lighting and Zn concentrations significantly impact lettuce growth, biochemical properties, and nutritional quality, particularly at the baby leaf stage. Full article

Innovation in cultivation methods is essential to address the growing challenges in agriculture, including abiotic and biotic stress, soil degradation, and climate change. Aeroponics, a particular type of hydroponics, presents a promising solution by improving yield and resource use efficiency, especially in controlled environments such as plant factories with artificial lighting (PFALs). Additionally, non-thermal plasma (NTP), a partially ionized gas containing reactive oxygen and nitrogen species, can affect plant development and physiology, further enhancing crop production. The objective of this study was to explore the potential of NTP as an innovative method to enhance crop production by treating the nutrient solution in aeroponic systems. During this study, three experiments were conducted to assess the effects of NTP-treated nutrient solutions on baby leaf lettuce (Lactuca sativa L.) aeroponically grown indoors. The nutrient solution was treated with ionized air in a treatment column separated from the aeroponic system by making the ionized air bubble from the bottom of the column. After 2 min of NTP application, a pump took the nutrient solution from the treatment column and sprayed it on the roots of plants. Various frequencies of NTP application were tested, ranging from 2.5% to 50% of irrigation events with nutrient solution activated with NTP. Results indicated that low-frequency NTP treatments (up to 5% of irrigations) stimulated plant growth, increasing leaf biomass (+18–19%) and enhancing the concentration of flavonoids (+16–18%), phenols (+20–21%), and antioxidant capacity (+29–53%). However, higher NTP frequencies (25% and above) negatively impacted plant growth, reducing fresh and dry weight and root biomass, likely due to excessive oxidative stress. The study demonstrates the potential of NTP as a tool for improving crop quality and yields in aeroponic cultivation, with optimal benefits achieved at lower treatment frequencies. Full article

Plant factories with artificial lighting (PFALs) are a notable choice for urban agriculture due to the system’s benefits, where light can be manipulated to enhance the product’s yield and quality. Our objective was to test the effect of light spectra with different red-blue combinations and white light on the growth, physiology, and overall quality of three baby-leaf vegetables (green lettuce, kale, and pak choi) grown in a restaurant’s PFAL. Leaf mass per area was lower under the most blue-containing treatments in all species. The performance indices (PI_abs and PI_tot) of the photosynthetic apparatus were lower under more red light with the exception of PI_abs in pak choi. Total soluble solids accumulation was diminished under most of the blue-containing LEDs, while total phenolics and antioxidant activity were induced by red-blue environments rich in blue light. Moreover, chlorophyll and carotenoid accumulation was also enhanced under blue-rich light treatments. Nitrate content was the lowest under monochromatic blue in all species. Finally, the employees were asked about their views on the PFAL within the restaurant’s compounds and they expressed positive opinions. Overall, a light environment including red and blue wavelengths proved beneficial for baby leafy vegetable production in terms of yield and quality. Full article

The market demand for baby leaf lettuce is constantly increasing, while safety has become one of the most important traits in determining consumer preference driven by human health hazards concerns. In this study, the performance of visible and near-infrared (vis/NIR) spectroscopy was tested in discriminating pesticide-free against pesticide-treated lettuce plants. Two commercial fungicides (mancozeb and fosetyl-al) and two insecticides (deltamethrin and imidacloprid) were applied as spray solutions at the recommended rates on baby leaf lettuce plants. Untreated-control plants were sprayed with water. Reflectance data in the wavelength range 400–2500 nm were captured on leaf samples until harvest on the 10th day upon pesticide application, as well as after 4 and 8 days during post-harvest storage at 5 °C. In addition, biochemical components in leaf tissue were also determined during storage, such as antioxidant enzymes’ activities (peroxidase [POD], catalase [CAT], and ascorbate peroxidase [APX]), along with malondialdehyde [MDA] and hydrogen peroxide [H₂O₂] content. Partial least square discriminant analysis (PLSDA) combined with feature-selection techniques was implemented, in order to classify baby lettuce tissue into pesticide-free or pesticide-treated ones. The genetic algorithm (GA) and the variable importance in projection (VIP) scores identified eleven distinct regions and nine specific wavelengths that exhibited the most significant effect in the detection models, with most of them in the near-infrared region of the electromagnetic spectrum. According to the results, the classification accuracy of discriminating pesticide-treated against non-treated lettuce leaves ranged from 94% to 99% in both pre-harvest and post-harvest periods. Although there were no significant differences in enzyme activities or H₂O₂, the MDA content in pesticide-treated tissue was greater than in untreated ones, implying that the chemical spray application probably induced a stress response in the plant that was disclosed with the reflected energy. In conclusion, vis/NIR spectroscopy appears as a promising, reliable, rapid, and non-destructive tool in distinguishing pesticide-free from pesticide-treated lettuce products. Full article

Lettuce (Lactuca sativa L.) is a popular leafy vegetable valued for its dietary fiber, antioxidants, and beneficial vitamins. This study presents a comprehensive spatio-temporal analysis of the lettuce metabolome, revealing complex dynamics in metabolite accumulation influenced by plant age, leaf position, proximodistal distribution within a leaf, and head closure. Samples were collected from plants at five maturity stages (ranging from baby leaf to full commercial maturity and eventually to bolting) and from five leaf positions (from the apex to the base of each plant). A widely targeted metabolomics approach identified 1905 compounds, with flavonoids, phenolic acids, and lipids as the largest classes. Younger plants exhibited higher levels of flavonoids, while older plants accumulated more saccharides and amino acids. Metabolites showed distinct proximodistal distributions, with flavonoids and vitamins concentrated at leaf tips and terpenoids declining from base to tip. Head closure significantly reduced levels of flavonoids, retinol (vitamin A1), and riboflavin (vitamin B2), while it was associated with increased content of other beneficial vitamins, such as thiamine (B1), pantothenate (B5), and pyridoxine (B6). Broad-sense heritability (H²) estimates for metabolites yielded mean H² values of 0.648 and 0.743 for plants at baby-leaf and commercial maturity stages, respectively. The overall highest heritability was observed in tannins (H² = 0.909) in younger plants and chalcones (H² = 0.894) in older plants, suggesting strong genetic control over specific metabolite classes and subclasses. These findings offer a robust framework for optimizing lettuce’s nutritional profile by linking metabolite distributions to developmental processes, plant architecture, and genetic regulation. By leveraging these insights, breeders and producers can develop targeted strategies to enhance metabolite content through optimized breeding and harvesting strategies. Full article

With the global population projected to reach 8.6 billion by 2050 and urbanization on the rise, sustainable food production in cities becomes imperative. Vertical farming presents a promising solution to meet this challenge by utilizing space-efficient, controlled-environment agriculture techniques. In a vertical farming system, high quality, high nutritional value products can be produced with minimum water consumption, using LEDs as energy-efficient light sources. Microgreens are a new market category of vegetables among sprouts and baby leaf greens. The most critical challenge in their cultivation is the choice of growing medium, lighting, and light spectrum, which affect photosynthesis, plant growth, and yield. This review explores various cultivation methods, including hydroponics, within the context of vertical farming. Using current research, it investigates the effect of LED lighting on the physiological properties and growth of microgreens and baby leaf lettuce, but further research is needed to determine the response of the varieties and the optimal light spectrum ratios to meet their needs. Full article

Over two billion people worldwide suffer from micronutrient deficiencies. Biofortifying vegetables can enhance micronutrient intake through the diet. This study assessed the biofortification of indoor-grown baby-leaf lettuce using aeroponics. Four experiments, two each, were conducted by adding different concentrations of Zn (from 10 to 450 µM) or Cu (from 3 to 250 µM) into a nutrient solution. A fifth experiment was conducted by simultaneously adding to the nutrient solution the optimal concentration of I (5 µM) and Se (13 µM), chosen on the basis of previous works, and the optimal concentration of Zn (250 µM) and Cu (150 µM), chosen on the basis of the results obtained in the first four experiments. Leaf biomass, mineral concentrations, chlorophylls, carotenoids, phenols, flavonoids, nitrates, and antioxidant capacity were measured 21 days after transplanting. Higher concentrations of Cu, Zn, I, or Se in the nutrient solution led to an increase in their concentrations in lettuce leaves, without affecting the growth or leaf quality of lettuce plants. The simultaneous application of I with the other elements induced a higher accumulation in leaves compared to when I is applied alone. One hundred grams of lettuce leaves biofortified with Se, I, Cu, and Zn would provide the 6.1%, 35.3%, and 263.0% of Adequate Intake for Cu, Se, and I, respectively, and 4.5% of Population Reference Intake for Zn. Our results suggest that simultaneously biofortifying baby-leaf lettuce with these four minerals is a practical and convenient way to integrate these micronutrients into the diet without reducing the yield or quality of lettuce. Full article

The increase in vegetable consumption has underlined the importance of minimizing the risks associated with microbiological contamination of fresh produce. The critical stage of the vegetable washing process has proven to be a key point for cross-contamination and the persistence of pathogens. In this context, the agri-food industry has widely adopted the use of disinfectants to reduce the bacterial load in the wash water. Therefore, we conducted laboratory-scale experiments in order to demonstrate the antimicrobial activity of disinfectants used in the wash tank of agro-food industries. Different wash water matrices of shredded lettuce, shredded cabbage, diced onion, and baby spinach were treated with sodium hypochlorite (NaClO), chlorine dioxide (ClO₂), and per-oxyacetic acid (PAA) at recommended concentrations. To simulate the presence of pathogenic bacteria, a cocktail of E. coli O157:H7 was inoculated into the process water samples (PWW) to determine whether concentrations of disinfectants inhibit the pathogen or bring it to a viable non-culturable state (VBNC). Hereby, we used quantitative qPCR combined with different photo-reactive dyes such as ethidium monoazide (EMA) and propidium monoazide (PMA). The results indicated that concentrations superior to 20 ppm NaClO inhibit the pathogen E. coli O157:H7 artificially inoculated in the process water. Concentrations between 10–20 ppm ClO₂ fail to induce the pathogen to the VBNC state. At concentrations of 80 ppm PAA, levels of culturable bacteria and VBNC of E. coli O157:H7 were detected in all PWWs regardless of the matrix. Subsequently, this indicates that the recommended concentrations of ClO₂ and PAA for use in the fresh produce industry wash tank do not inhibit the levels of E. coli O157:H7 present in the wash water. Full article

Lettuce (Lactuca sativa) is a leafy vegetable that provides a valuable source of phytonutrients for a healthy human diet. The assessment of plant growth and composition is vital for determining crop yield and overall quality; however, classical laboratory analyses are slow and costly. Therefore, new, less expensive, more rapid, and non-destructive approaches are being developed, including those based on (hyper)spectral reflectance. Additionally, it is important to determine how plant phenotypes respond to fertilizer treatments and whether these differences in response can be detected from analyses of hyperspectral image data. In the current study, we demonstrate the suitability of hyperspectral imaging in combination with machine learning models to estimate the content of chlorophyll (SPAD), anthocyanins (ACI), glucose, fructose, sucrose, vitamin C, β-carotene, nitrogen (N), phosphorus (P), potassium (K), dry matter content, and plant fresh weight. Five classification and regression machine learning models were implemented, showing high accuracy in classifying the lettuces based on the applied fertilizers treatments and estimating nutrient concentrations. To reduce the input (predictor data, i.e., hyperspectral data) dimension, 13 principal components were identified and applied in the models. The implemented artificial neural network models of the machine learning algorithm demonstrated high accuracy (r = 0.85 to 0.99) in estimating fresh leaf weight, and the contents of chlorophyll, anthocyanins, N, P, K, and β-carotene. The four applied classification models of machine learning demonstrated 100% accuracy in classifying the studied baby leaf lettuces by phenotype when specific fertilizer treatments were applied. Full article

The aim of this research is to introduce innovative cultivation practices that result in reduced nitrate levels in baby leaf lettuce grown under vertical farming conditions while maintaining high productivity. For this reason, three experiments were conducted. The first experiment focused on the impact of two “white” light spectra with a blue:green:red:far-red ratio of 14:32:43:10 (B_lowR_high) and 21:34:36:7 (B_highR_low). The second experiment assessed the effects of two nitrogen supply conditions: sufficient total nitrogen (N₁₅) and limited total nitrogen (N₅), and foliar biostimulant application. In the third experiment, the impact of replacing the nutrient solution in the N₁₅ treatment with tap water for an additional 24 h (TW24) on leaf nitrate content was examined. Results from the lighting experiment revealed no significant effects on agronomical parameters or nitrate content between the two light spectra. Reducing nitrogen content in the nutrient solution reduced leaf nitrate content but negatively influenced agronomical characteristics. Biostimulant application and replacing the nutrient solution with water reduced leaf nitrate content compared to the control and positively affected growth. The most favorable outcomes were observed in plants supplied with sufficient nitrogen and foliar biostimulant but also cultivated for an additional 24 h with tap water (Sp-N₁₅-TW24). Full article

The use of high tunnels, which allows growers to extend their season and improve yields, is increasing in the Southeastern U.S., yet growers face challenges related to weed and disease management, particularly in organic systems. On-station experiments were conducted during fall 2021 and spring 2022 in a split-plot design to assess the efficacy of anaerobic soil disinfestation (ASD) in high tunnels for the organic production of direct-seeded baby leaf lettuce. Soil treatments (ASD, Compost, and Control) and lettuce types (romaine and oakleaf cultivars) were included in whole plots and subplots, respectively. The ASD-treated soils received molasses and granular organic fertilizer as carbon and nitrogen sources. The Compost treatment involved the application of yard waste-based compost and the same organic fertilizer, while the Control soils received organic fertilizer only. The ASD treatment period lasted 8 days rather than the typical 21-day period evaluated in Florida. Crop yield, biometrics (leafy dry matter content, specific leaf area, specific leaf weight), and lettuce quality attributes (leaf color, soluble solids content, total titratable acidity, ferric reducing antioxidant power, ascorbic acid content, total phenolics) were assessed following harvest. In both trials, numerical differences in lettuce fresh weight yield between soil treatments were evident, though not statistically significant. Differences in leaf quality attributes were driven by lettuce cultivar rather than soil treatments. Bottom rot incidence caused by Rhizoctonia solani was reduced by 93% and 87% in the ASD-treated plots compared with the Compost- and Control-treated soils during the spring 2022 trial. The ASD-treated soils had a reduced population density of broadleaf weeds in both baby leaf lettuce production trials. The current study presents novel evidence of the potential of integrating ASD into HT organic production systems without reducing the yield and quality attributes of direct-seeded baby leafy greens compared with common grower practices. Full article

The use of peat, the standard substrate used for soilless cultivation of horticultural crops, is becoming of increasing concern as peat is a non-renewable resource and its extraction can degrade wetland ecosystems, creating a strong environmental impact. For this reason, the search for organic materials that can totally or partially replace peat has become increasingly important. In this research, three types of composts (C1, C2, C3), derived from cardoon biomass mixed in different volumes with woody and/or fruit wastes, were utilized as the constituents of growing media, at two dilution rates with peat (60:40 and 30:70 v:v), to assess their effect on the growth and quality of baby leaf lettuce in a greenhouse trial. The two cultivars Imperiale and Verde d’Inverno, belonging to the butterhead and romaine lettuce types, respectively, were employed. Plant performance and yield were unaffected or were positively affected by compost-containing growing medium compared to the control. The cultivars responded differently to the growing medium; the Imperiale showed the highest yield with C1 compost at a 60% rate while the Verde d’Inverno with the C2 was at 30%. The total chlorophyll, carotenoids, and ascorbic acid were found higher in the Verde d’Inverno than in the Imperiale variety while the total polyphenols, flavonoids, and antioxidant activity were lower. Also, the content of chlorophylls as well as of antioxidant compounds and antioxidant activity were differently affected by the growing medium, depending on the lettuce cultivar. The results obtained indicate that cultivated cardoon waste-based compost is a promising constituent of the growing media for baby leaf production. The specific varietal response observed should be considered to optimize both yield and product quality. Full article

Fusarium oxysporum f. sp. lactucae is one of the most aggressive baby-lettuce soilborne pathogens. The application of Trichoderma spp. as biocontrol agents can minimize fungicide treatments and their effective targeted use can be enhanced by support of digital technologies. In this work, two Trichoderma harzianum strains achieved 40–50% inhibition of pathogen radial growth in vitro. Their effectiveness in vivo was surveyed by assessing disease incidence and severity and acquiring hyperspectral and thermal features of the canopies being treated. Infected plants showed a reduced light absorption in the green and near-red regions over time, reflecting the disease progression. In contrast, Trichoderma-treated plant reflectance signatures, even in the presence of the pathogen, converged towards the healthy control values. Seventeen vegetation indices were selected to follow disease progression. The thermographic data were informative in the middle–late stages of disease (15 days post-infection) when symptoms were already visible. A machine-learning model based on hyperspectral data enabled the early detection of the wilting starting from 6 days post-infection, and three different spectral regions sensitive to baby-lettuce wilting (470–490 nm, 740–750 nm, and 920–940 nm) were identified. The obtained results pioneer an effective AI-based decision support system (DSS) for crop monitoring and biocontrol-based management. Full article