Search Results (667)

Proper substrate moisture management is essential for producing high-quality seedlings in nurseries. This study aimed to evaluate the morphological and physiological quality of lettuce (Lactuca sativa L.) and tomato (Solanum lycopersicum L.) seedlings subjected to different substrate moisture levels, monitored by weighing lysimetry under protected environment conditions. Four experiments were conducted over two growing seasons (2019 and 2020) using six irrigation treatments corresponding to 80, 70, 60, 50, and 40% of the substrate water-holding capacity, in addition to the conventional irrigation management adopted by the grower (Control). Water consumption, morphological traits, root architecture, gas exchange, chlorophyll fluorescence, and photosynthetic pigments were assessed. Cumulative irrigation water applied ranged from 77 to 92 mm in lettuce and from 91 to 132 mm in tomato. Reducing substrate moisture to 40% negatively affected seedling growth, root development, and physiological performance in both species. In tomato, stomatal conductance decreased by up to 90%, accompanied by a decline in Fv/Fm from 0.78 to 0.70. Both lettuce and tomato tolerated moderate reductions in substrate moisture (60–70% holding capacity) without significant losses in growth or gas exchange performance. However, the highest seedling quality was achieved under the grower-managed Control and the 80% substrate moisture treatment, although the traits contributing to this response differed between species. In lettuce, favorable performance was associated with growth, pigment-related traits, and photochemical efficiency, whereas in tomato superior seedling quality was linked to shoot growth, root development, and gas exchange characteristics. These findings support the use of species-specific irrigation strategies to improve seedling quality in nursery production. Full article

Improving the nutritional quality of food through advanced and sustainable agricultural practices has become a key objective of modern vegetable crop production. Emphasis is placed on increasing the content of health-promoting bioactive compounds, such as vitamins and polyphenols, particularly flavonoids whose accumulation is strongly affected by various biotic and abiotic stress factors. To mitigate stress-induced limitations and enhance plant performance, biostimulants are increasingly applied. Among them, Trichoderma spp. are widely recognized for their ability to promote plant growth and resilience, primarily through enzymatic activity and the production of bioactive metabolites. The aim of this study was to evaluate the potential of the native Trichoderma sp. strain STP8 to enhance the production of bioactive compounds through seed and soil applications at planting and 26 days after planting (DAP), applied individually or in combination. A spore suspension (4 × 10⁶ spores mL⁻¹) was used. The experiment was arranged in a randomized complete block design with five replicates. At harvest (43 DAP), dry matter, ascorbic acid, chlorophyll, and carotenoid contents were determined. Additionally, flavonoids and non-flavonoids, total phenolics, individual phenolic compounds, and antioxidant capacity were analyzed. Achieved results demonstrate that the effects of the native Trichoderma sp. strain STP8 on lettuce secondary metabolism and antioxidant properties are strongly dependent on the developmental stage at which inoculation is performed, providing further insight into the stage-specific interactions between plans and Trichoderma. Practically, a single application at planting proved to be the most effective strategy for enhancing the accumulation of bioactive compounds, indicating that optimized application timing may improve the efficacy of Trichoderma-based biostimulants, while avoiding unnecessary repeated applications. These findings support the potential use of native Trichoderma strains as sustainable tools for improving the nutritional and functional quality of lettuce. Further research integrating physiological, biochemical, and molecular analyses is required to elucidate the mechanisms by which the native Trichoderma sp. strain STP8 regulates the biosynthesis of bioactive compounds in lettuce. Full article

Fungal pathogens cause severe yield losses in lettuce production worldwide. We developed transgenic lettuce lines overexpressing the ch5B chitinase gene from Phaseolus vulgaris (bean) under the regulation of the rbcS1 (ribulose-1,5-bisphosphate carboxylase small subunit) promoter. Molecular characterization confirmed stable transgene integration and expression across the selected lines. In vitro assays demonstrated that transgenic leaf extracts significantly inhibited Rhizoctonia solani mycelial growth. Furthermore, inoculation assays in both seedlings and adult plants in the greenhouse showed a significant reduction in lesion areas compared to non-transgenic (NT) controls. Finally, two lines were evaluated in field trials, both showing agronomic substantial equivalence to the NT, satisfying international biosafety frameworks for commercial development. Among them, the ch5B 3-4 line appears to be the most promising candidate for further studies, as it showed slightly higher fresh weight compared to the NT under field conditions.: Full article

Lettuce (Lactuca sativa L.) is a widely consumed leafy vegetable cultivated globally, particularly under soilless systems to enable intensive and high-efficiency production. In these systems, precise nutrient solution management is essential, especially regarding calcium, an indispensable macronutrient involved in cell wall stabilization, membrane integrity, root development, and physiological responses to stress. This study evaluated the morphological and nutritional performance of crisp lettuce cultivars Mônica SF 31 and Veneranda grown using a nutrient film technique (NFT) system, using Calcário, Lithocal^®, and LT Supra^® as alternative calcium sources, alongside a control treatment. The experiment followed a randomized block design in a 4 × 2 factorial arrangement. Measured variables included root, leaf, and stem dry mass; stem length and diameter; and nutrient accumulation and gas exchange parameters. Data were subjected to analysis of variance and means were compared using Scott-knott test. Calcium supplementation significantly increased plant growth, with leaf fresh mass rising by 37% and root fresh mass by 56% compared to the control. Foliar calcium and magnesium concentrations were effectively enhanced by the treatments. Calcário, Lithocal^®, and LT Supra^® demonstrated effectiveness as calcium sources in soilless lettuce cultivation, promoting improved nutrient accumulation—particularly calcium and magnesium—and substantial gains in fresh biomass and root system development. Calcium supplementation is therefore recommended as a strategy to enhance productivity and crop quality in intensive soilless systems. Full article

A process-based developmental model was developed to predict leaf appearance and expansion in romaine lettuce (Lactuca sativa L. var. longifolia) using hourly air temperature and daily light integral as environmental inputs. The model consisted of two linked modules representing leaf appearance and individual leaf expansion as distinct biological processes. The leaf appearance module calculated the hourly leaf tip appearance rate as the product of a beta-type nonlinear temperature response function and a developmental stage weighting function based on growing degree days accumulated above a base temperature of 4 °C. The leaf expansion module estimated individual leaf expansion using photothermal age, a Gompertz growth function, and a leaf length–area allometric relationship, with potential leaf length determined by the mean growing temperature and leaf rank. The optimum temperatures for leaf appearance rate and potential leaf length differed by approximately 6 °C (26.7 °C vs. 20.4 °C), indicating distinct temperature response patterns between the two developmental processes. Model calibration was performed using datasets (n = 437) collected from a temperature-gradient greenhouse with a nutrient film technique hydroponic system across the spring, summer, and autumn growing seasons, yielding an overall model efficiency (EF) of 0.92 and a root mean square error (RMSE) of 4.26 leaves for leaf appearance, and an EF of 0.80 and an RMSE of 448.1 cm² for leaf expansion. Independent model evaluation was also performed using datasets (n = 132) obtained from a commercial greenhouse with either a deep flow technique hydroponic system or a perlite-based substrate system across the same three growing seasons, yielding an EF of 0.96 and an RMSE of 2.24 leaves for leaf appearance, and an EF of 0.92 and an RMSE of 216.8 cm² for leaf expansion. These results demonstrate that the model effectively described leaf appearance and expansion in romaine lettuce across the tested soilless culture systems under greenhouse conditions, highlighting its potential as a leaf development module for integration into canopy photosynthesis and biomass production models. Full article

Hydroponic and soilless systems are increasingly adopted as low-cost, sustainable solutions for global food production, yet they remain highly susceptible to contamination by potential toxic elements (PTEs), particularly arsenic. While biochar is widely recognized as an effective amendment for mitigating PTE contamination in soil-based systems, its ability to alleviate PTE stress in hydroponic environments has been largely overlooked. The gap reveals a critical and underexplored frontier in controlled-environment agriculture, where extending biochar-based mitigation strategies could yield substantial benefits. Here, we evaluated whether Acacia auriculiformis wood biochar could alleviate arsenic (As) toxicity in lettuce (Lactuca sativa) grown in a continuous-flow hydroponic system. Using a completely randomized factorial design (arsenic species × dose × biochar) with three independent replicates per treatment, we tested biochar under 0.2 and 0.8 mg/L of As(III) and As(V). Arsenic significantly (p < 0.05) reduced lettuce growth, with As(III) being more toxic than As(V). Biochar significantly (p < 0.05) improved morphological traits (2.4–103%), cell membrane stability (5.5–12%), photosynthetic pigments (3–73%), and stress indicators proline (8–11%) and malondialdehyde (8–14%). Arsenic accumulated mainly in roots (1.7–2.63 mg/kg) and shoots (0.76–1.36 mg/kg), but biochar reduced accumulation by 28–47% in roots and 33–48% in shoots. Additionally, biochar enhanced nutrient uptake (K, P, Ca, Mg, B, Zn, Cu, S, Mn) at both arsenic levels. Overall, the results indicate that Acacia biochar can substantially reduce arsenic toxicity and improve plant physiological responses in continuous-flow hydroponics, highlighting its promise as a viable and scalable mitigation tool for safeguarding soilless food production systems against PTE contamination. Full article

Phenolic acids are considered important allelochemicals that can restrict nutrient uptake and inhibit plant growth. Most existing studies have focused on growth phenotypes and single nutrient changes under phenolic acid stress, while the coupled C:N:P balance responses of plant–soil systems remain poorly characterized. Ecological stoichiometry offers a holistic perspective to reveal the nutrient supply–demand mismatch underlying allelopathic inhibition by analyzing elemental ratio dynamics, thus deepening the mechanistic understanding of allelopathy beyond traditional single-indicator observations. Using lettuce (Lactuca sativa L.) as the test plant, this study investigated the effects of cinnamic acid (CA) and p-hydroxybenzoic acid (PHA) stress, combined with nitrogen (N), phosphorus (P), and their combined application (NP) on plant growth and plant C, N, and P stoichiometric characteristics. Soil C, N, and P contents and stoichiometric characteristics were further analyzed as supplementary indicators. The results showed that phenolic acid stress significantly reduced lettuce biomass: PHA decreased aboveground biomass by 40.11% and belowground biomass by 44.14%, with a stronger inhibitory effect than CA. Both phenolic acids induced marked stoichiometric imbalance, characterized primarily by a sharp decline in leaf nitrogen content; N content dropped by 49.80% under CA and 70.75% under PHA, corresponding to a 64.43% and 162.79% increase in leaf C:N ratio, and a 37.63% and 63.19% decrease in leaf N:P ratio, respectively. Nutrient addition alleviated these responses to varying degrees: N addition mainly promoted biomass recovery and elevated plant N status, P addition optimized elemental ratios, and combined NP application yielded the strongest overall recovery. Correlation and redundancy analyses indicated that soil C, N, and P stoichiometric characteristics were closely associated with plant growth, with soil organic carbon and total phosphorus identified as major explanatory variables associated with plant growth. Overall, phenolic acid stress altered plant stoichiometric characteristics and growth, as well as soil C, N, and P stoichiometric characteristics, while nutrient addition partially alleviated these responses. These findings provide a stoichiometric perspective for understanding allelopathic stress and may offer a theoretical basis for nutrient management under continuous cropping conditions. Full article

Water scarcity and environmental degradation have emerged as critical challenges threatening sustainable agricultural development worldwide. This study hypothesized that organic substitution buffers the physiological stress of deficit irrigation on lettuce (Lactuca sativa L.), and that this buffering effect of organic substitution can be quantified using AquaCrop to optimize irrigation schedules. Field experiments were conducted to evaluate the interactive effects of irrigation levels and organic/urea fertilizer rates on soil moisture, lettuce growth and yield during two growing seasons (April to May and September to October 2024) in Songjiang, Shanghai. Six treatments combining two irrigation levels (full irrigation at 100% of crop evapotranspiration (ETc) and deficit irrigation at 60% ETc) with three fertilization levels (300 kg/ha urea, 150 kg/ha urea + 15 t/ha organic fertilizer, and 150 kg/ha urea) were conducted. AquaCrop was calibrated and validated using field observations. The results demonstrated that organic substitution under deficit irrigation preserved soil moisture, canopy development, and fresh yield at levels comparable to full irrigation and nitrogen fertilization, whereas 50% nitrogen alone caused substantial yield reduction. AquaCrop showed satisfactory performance in simulating lettuce growth under organic substitution, with normalized root mean square error (NRMSE) values of 3.07%~21.42%, 5.02%~20.11%, and 8.22%~20.95% for soil water content, canopy cover, and fresh yield, respectively. Using the validated model, scenario analysis across the different precipitation years revealed that lettuce yield was most responsive to irrigation during the seedling stage, followed by the rosette stage and cupping stage. Specifically, 100% ETc during the seedling and rosette stages was suggested for dry years; 100% ETc at the seedling stage combined with 80% to 100% ETc at the rosette stage for normal years; and more flexible strategies (60% to 100% ETc at the seedling stage) for wet years based on model predictions. These irrigation strategies, combined with organic substitution, can achieve above 90% of the potential yield of the full irrigation and nitrogen treatment. These findings offer preliminary guidance for irrigation and fertilization management of lettuce under the experimental climate and soil conditions, while further validation across diverse cultivars and environments is needed before broader application. Full article

This study evaluated the effects of peat-based organomineral fertilizers with different compositions and Bacillus spp. inoculation on the growth and nutrient accumulation of loose-leaf lettuce grown under summer and winter conditions. Two independent greenhouse experiments were conducted using a randomized complete block design with eight treatments: no basal fertilized control (T1); conventional mineral fertilization (T2); peat-based organomineral fertilizers containing 50% (T3), 40% (T4), or 30% peat (T5); and the corresponding formulations supplemented with Bacillus subtilis, Bacillus megaterium, and Bacillus aryabhattai (T6–T8). All fertilized treatments were standardized to supply the same P rate. Multivariate analyses revealed a strong effect of fertilization strategy on plant growth and nutritional status. In both seasons, fertilized treatments significantly outperformed the control, while organomineral fertilizers performed similarly to or better than conventional mineral fertilization. The greatest shoot fresh mass and nutrient accumulation were observed in formulations containing lower peat proportions and higher mineral nutrient density, particularly when combined with Bacillus spp. inoculation. In the summer experiment, the 40% peat formulation supplemented with Bacillus spp. (T7) produced the highest shoot fresh mass (197.57 g plant⁻¹), whereas in the winter experiment the highest value was obtained with the 30% peat formulation supplemented with Bacillus spp. (T8; 157.86 g plant⁻¹). These treatments also exhibited greater accumulation of macronutrients and micronutrients, particularly N, P, K, Fe, Mn, and Zn. The results indicate that the performance of peat-based organomineral fertilizers was influenced by the balance between the organic matrix and mineral fraction, as well as by seasonal growing conditions. In addition, Bacillus spp. inoculation was associated with improved performance of formulations with greater mineral nutrient density but did not compensate for less favorable fertilizer compositions. Under the conditions evaluated, peat-based organomineral fertilizers containing lower peat proportions and supplemented with Bacillus spp. performed similarly to or better than conventional mineral fertilization and promoted greater lettuce growth and nutrient accumulation than the non-fertilized control. These findings are limited to a single lettuce cultivar grown in pots under greenhouse conditions across two seasonal experiments conducted at one location. Full article

Agronomic biofortification represents an effective strategy to counteract hidden hunger in humans. Salts and synthetic chelates are widely used as foliar or root applications for enriching vegetables with mineral nutrients. Recently, biochelates have been proposed as a sustainable alternative to synthetic chelates, especially peptide-based biochelates that combine the beneficial role of peptides as biostimulants and chelating agents. This study investigated the impact of multiple foliar applications of two peptide-based biochelates for enhancing Fe and Zn in leaves of hydroponically grown lettuce. No significant differences were observed in the fresh and dry weight of lettuce shoots, leaf pigments, leaf antioxidant activity and leaf macronutrient profile, while a significant increase in biochelate treatments was observed in leaf Fe and Zn concentrations in comparison with untreated control (+38.1% and +44.1%, respectively). Leaf concentration of Fe and Zn in biochelate treatments allowed to estimate that 100 g of biofortified fresh lettuce shoots per day in the human diet can contribute to Population Reference Intake from 7.9 to 11.5% for Fe and from 3.3 to 3.9% for Zn. Moreover, Zn-peptide treatments reduced nitrate concentration with respect to control and Fe-peptide (−9% and −11%, respectively), increasing the quality of lettuce leaves. Overall, peptide-based biochelates proved to be a promising, environmentally friendly fertilizer for lettuce biofortification, enhancing Fe and Zn concentration without impairing yield and leaf quality. Full article

The seedling production stage of lettuce (Lactuca sativa L.) is crucial for crop success, as it determines the initial quality of the plants. The use of seeds with rapid and uniform germination is essential to ensure proper seedling establishment. Among sustainable alternatives for water management, irrigation with ozonated water stands out due to its disinfectant potential and its ability to stimulate plant physiology. This study evaluated the effects of irrigation with ozonated water on the production and development of lettuce seedlings. The experiment was conducted in a completely randomized design (CRD) arranged in a 2 × 2 factorial scheme, with four replications. Two lettuce cultivars were tested: one with smooth leaves and another with crisp leaves. The variables analyzed included germination parameters (final percentage, germination index and mean germination rate, uniformity, and time to reach 10, 50, and 90% germination), as well as initial growth parameters (total height, shoot and root height, and dry matter content). Analyses were performed on 20 seedlings per cultivar. Irrigation with ozonated water promoted significant growth (p < 0.05) of the shoot and root growth, with increases of 16.90 and 4.99% for the smooth-leaf cultivar, and 24.27 and 9.26% for the crisp-leaf cultivar, compared to the control. Ozone application did not alter the microbiological, physical, or chemical parameters of the water. These growth-promoting effects are likely associated with increased oxygenation of the root zone, enhanced oxidation of organic matter in the substrate, and improved nutrient availability promoted by ozone-derived radicals, which may also optimise root respiration and reduce pathogenic pressure. The applied concentration of 5 mg L⁻¹ O₃ over a 25-day seedling production cycle proved effective and did not cause phytotoxic effects. Irrigation with ozonated water is an efficient and environmentally safe alternative for producing vigorous lettuce seedlings. Full article

This study investigated the efficacy of fruit peel-derived fertilizers from banana (Musa), orange (Citrus × sinensis), and mixed fruit peels in promoting lettuce (Lactuca sativa) growth in a hydroponic system as a sustainable alternative to synthetic nutrient solutions. The research determined the optimal concentration and application through trials, comparing effectiveness across concentrations and light exposure conditions within the first 1–2 weeks of cultivation. Findings revealed that optimal concentrations of 400–1000 g of peels per liter of water and a 3-L fertilizer combination yielded favorable outcomes under direct sunlight. The study concludes that banana and mixed peel fertilizers supported robust lettuce growth, with banana being the most effective. Full article

Developing sustainable strategies for natural resource management and conservation under shifting climatic scenarios is increasingly necessary due to exacerbated abiotic stresses, such as salinity. Under salt stress, several negative effects are observed in plants, particularly in leafy vegetables such as lettuce (Lactuca sativa L.). To mitigate the effects of saline stress from brackish water, several strategies have been adopted, including hydroponic cultivation. Therefore, this study aimed to determine the effects of variations in nutrient solution concentration and volume per lettuce plant cultivated in a nutrient film technique (NFT) hydroponic system using brackish water. The experiment was conducted using a randomized complete block design in a 2 × 2 × 2 factorial scheme, combining two levels of water electrical conductivity (ECw of 0.3 and 5.0 dS m⁻¹), two nutrient solution concentrations (NSC of 50 and 100%), and two nutrient solution volumes (NSV of 1 and 2 L plant⁻¹), with four replications. Growth, production, and water productivity variables were evaluated at 20 and 25 days following the imposition of treatments. The responses of the variables to saline stress varied according to the evaluation period (20 and 25 days), depending on the NSC and NSV levels. At the end of the 25-day cycle, it can be concluded that for lettuce cultivation using brackish water, the NSC can be reduced to 50% and provide an NSV of 2 L plant⁻¹. Under these growing conditions, leaf fresh matter production loss was approximately 40% lower than under cultivation without saline stress, which yielded 144.11 g plant⁻¹ under 100% NSC and an NSV of 2 L plant⁻¹. In contrast, water productivity of fresh matter was similar, at 78.68 and 76.55 g L⁻¹, respectively. Full article

Understanding the ecological impacts of nanoplastics requires evaluation metrics beyond conventional mass-based concentrations. In this study, we investigated the generation, characterization, and phytotoxic effects of environmentally relevant plastic particles in hydroponically grown lettuce (Lactuca sativa), focusing on particle size, shape, and number concentration. Low-density polyethylene (LDPE) was degraded using an advanced oxidation process, demonstrating that substantial oxidative degradation is required for the formation of nanoplastics; the resulting LDPE particles exhibited a broad size distribution ranging from the nanoscale to the micrometer scale, containing nanoscale domains (peak size ~20 nm, average size ~30 nm), and showed predominantly ellipsoidal morphologies derived from cross-linked polymer regions. In contrast, polystyrene (PS) particles of defined sizes (~600 nm and ~2000 nm) were prepared via mechanical fragmentation, exhibiting sharp-edged, flake-like morphologies. Laser scanning microscopy revealed uptake and translocation of LDPE particles from roots to aerial tissues, whereas larger PS particles showed limited transport. Growth inhibition analysis based on particle number concentration (10¹⁰–10¹⁷ particles/mL) showed a stepwise concentration–response relationship for LDPE particles, with inhibition levels increasing from approximately ~30% at low concentrations to high levels of inhibition at the highest concentrations In contrast, PS particles caused significant root damage (e.g., clear surface disruption observed in microscopy) and growth inhibition (~30–40%) even at relatively low number concentrations (~10¹⁰–10¹² particles/mL), likely due to their sharp-edged morphology. Overall, plant responses to plastic particles were governed by an interplay of size, shape, and number concentration, highlighting the importance of particle morphology and concentration metrics in agroecosystem risk assessment. Full article

Mercury contamination in water poses severe environmental and health risks, requiring efficient and sustainable removal strategies. In this study, rice husk (RH), rice husk-derived materials, including rice ash (RHA), and Mobil Composition of Matter No. 41 (MCM-41) were evaluated as adsorbents for Hg(II) removal in aqueous systems. Among the tested materials, MCM-41 exhibited superior adsorption performance, achieving up to 98% Hg(II) removal under optimal conditions (pH 6.8, 3 g L⁻¹ of adsorbent, and a pollutant concentration of 0.90 mg L⁻¹). Adsorption followed a pseudo-second-order kinetic model and was best described by the Langmuir isotherm, indicating monolayer adsorption. The maximum adsorption capacity reached 0.80 mg g⁻¹. Thermodynamic analysis revealed that the process was spontaneous and exothermic, primarily governed by coordination interactions and hydrogen bonding with surface silanol groups. The adsorbent’s applicability was further assessed in distilled water, synthetic industrial wastewater, and river water. Although high removal efficiencies were maintained, a decrease was observed in complex matrices due to competition from coexisting ions. Reusability tests demonstrated that MCM-41 retained its performance over four adsorption cycles. Environmental safety was evaluated through ecotoxicological and microbiological assays. Daphnia magna exhibited high sensitivity to Hg(II) (EC₅₀ values of 0.0220 mg L⁻¹ at 24 h and 0.0158 mg L⁻¹ at 48 h), while treated samples showed improved germination indices of Lactuca sativa, particularly in distilled and river water. However, residual toxicity persisted in industrial wastewater matrices. Overall, rice husk-derived MCM-41 is a promising and sustainable adsorbent for Hg(II) removal, though further optimization is needed to mitigate residual toxicity in complex water matrices. Full article