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Lettuce is the most highly consumed raw leafy vegetable crop eaten worldwide, making it nutritionally important in spite of its comparatively low nutrient density in relation to other vegetables. However, the perception of bitterness caused by high levels of sesquiterpenoid lactones and comparatively low levels of sweet tasting sugars limits palatability. To assess variation in nutritional and taste-related metabolites we assessed 104 members of a Lactuca sativa cv. Salinas x L. serriola (accession UC96US23) mapping population. Plants were grown in three distinct environments, and untargeted NMR and HPLC were used as a rapid chemotyping method, from which 63 unique Quantitative Trait Loci (QTL) were identified. We were able to identify putative regulatory candidate genes underlying the QTL for fructose on linkage group 9, which accounted for up to 36 % of our population variation, and which was stable across all three growing environments; and for 15-p-hydroxyyphenylacetyllactucin-8-sulfate on linkage group 5 which has previously been identified for its low bitterness, while retaining anti-herbivory field effects. We also identified a candidate gene for flavonoid 3,5- hydroxylase underlying a polyphenol QTL on linkage group 5, and two further candidate genes in sugar biosynthesis on linkage groups 2 and 5. Collectively these candidate genes and their associated markers can inform a route for plant breeders to improve the palatability and nutritional value of lettuce in their breeding programmes.

Cadmium (Cd) contamination in agricultural soil brings severe health risks through the dietary intake of Cd‐polluted crops. The comprehensive role of pectin in lowering Cd accumulation is investigated through low Cd accumulated (L) and high Cd accumulated (H) cultivars of L. sativa. The significantly different Cd contents in the edible parts of two L. sativa cultivars are accomplished by different Cd transportations. The pectin is the dominant responsive cell wall component according to significantly increased uronic acid contents and the differential Cd absorption between unmodified and modified cell wall. The chemical structure characterization revealed the decreased methyl esterification in pectin under Cd treatment compared with control. Significantly brighter LM19 relative fluorescence density and 40.82% decreased methanol in the root pectin of L cultivar under Cd treatment (p < 0.05) supported that the de‐methyl esterification of root pectin is more significant in L cultivar than in H cultivar. The pectin de‐methyl esterification of L cultivar is achieved by the upregulation of pectin esterases and the downregulation of pectin esterase inhibitors under Cd treatments, which has facilitated the higher Cd‐binding of pectin. Our findings provide deep insight into the differential Cd accumulation of L. sativa cultivars and contribute to the understanding the pollutant behaviors in plants. Summary statement: Cd‐pollution safe cultivar (Cd‐PSC) with low Cd accumulation in edible parts is a promising strategy to minimize the Cd pollution risk of crops and guarantee food security even in Cd pollution soil. Our study has illustrated the role of root pectin de‐methyl esterification in determining the Cd accumulation in L. Sativa through comprehensive physiological, chemical characterization, and molecular methods, supporting de‐methyl esterification of pectin in L cultivar plays a more prominent role in root pectin detaining Cd. We believe that our study makes a significant contribution to understanding different Cd accumulation mechanisms and molecular‐assistant Cd‐PSC breeding of Lactuca Sativa. [ABSTRACT FROM AUTHOR]

Crop monitoring can promptly reflect the growth status of crops. However, conventional methods of growth monitoring, although simple and direct, have limitations such as destructive sampling, reliance on human experience, and slow detection speed. This study estimated the fresh weight of lettuce (Lactuca sativa L.) in a plant factory with artificial light based on three-dimensional (3D) reconstruction technology. Data from different growth stages of lettuce were collected as the training dataset, while data from different plant forms of lettuce were used as the validation dataset. The partial least squares regression (PLSR) method was utilized for modeling, and K-fold cross-validation was performed to evaluate the model. The testing dataset of this model achieved a coefficient of determination (R2) of 0.9693, with root mean square error (RMSE) and mean absolute error (MAE) values of 3.3599 and 2.5232, respectively. Based on the performance of the validation set, an adaptation was made to develop a fresh weight estimation model for lettuce under far-red light conditions. To simplify the estimation model, reduce estimation costs, enhance estimation efficiency, and improve the lettuce growth monitoring method in plant factories, the plant height and canopy width data of lettuce were extracted to estimate the fresh weight of lettuce in addition. The testing dataset of the new model achieved an R2 value of 0.8970, with RMSE and MAE values of 3.1206 and 2.4576. [ABSTRACT FROM AUTHOR]

Given the fluctuating availability of natural lighting throughout the year, supplemental light is frequently employed to maintain the optimal daily light integral (DLI) levels necessary for adequate plant growth. However, the use of supplemental light translates into higher operational costs. Recent reports suggest that plants can tolerate a day with low DLI following exposure to a day with high DLI from natural light. This was referred to as the 'carryover' effect. In such cases, supplemental lighting may not be necessary, resulting in energy savings. In this study, we determined if plants can withstand such DLI fluctuations over multiple days without compromising plant growth. Additionally, we calculated the energy requirements for trese treatments to evaluate the potential energy savings of the carryover effect. To test this, we cultivated lettuce plants (Lactuca sativa cv. 'Waldmand's Dark Green' and 'Rouxai') in a walk-in grow chamber, subjecting them to six different lighting treatments. Each treatment consisted of a day with a high DLI of 22.5 mol·m-2·d-1 followed by a varying number of consecutive days with low DLI, ranging from 1 to 5 days, with DLIs of 7.5, 11.25, 12.5, 13.13, and 13.5 mol·m-2·d-1 respectively. The combined DLI for each treatment, calculated as the average DLI across high and low DLI days, was maintained at 15 mol·m-2·d-1. Additionally, we included a control treatment where plants were exposed to a constant DLI of 15 mol·m-2·d-1. We measured plant growth rate, final fresh and dry weights, leaf number, leaf area, specific leaf area, light use efficiency, and relative pigment content to assess differences in plant growth under the different lighting regimes. We observed a decrease in biomass accumulation, as indicated by a 13% reduction in final dry weight only for the treatment involving one day of high DLI followed by one day of low DLI, compared to our control. We discovered that plants can tolerate multiple days of low DLI following a day with high DLI, in contrast to the optimal values reported in the literature. This finding can lead to reduced energy consumption for supplemental lighting and consequent operational cost savings. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lettuce (Lactuca sativa) is a globally significant leafy vegetable, valued for both its economic and nutritional contributions. The efficient conservation and use of the lettuce germplasm are crucial for breeding and genetic improvement. This study examined the genetic diversity and population structure of a core collection of the lettuce germplasm using genotyping by sequencing (GBS). A total of 7136 high-quality single-nucleotide polymorphisms (SNPs) were identified across nine chromosomes. Population analysis through Bayesian clustering and discriminant analysis of principal components (DAPC) revealed three distinct genetic clusters. Cluster 2 exhibited the greatest genetic diversity (He = 0.29, I = 0.44), while Cluster 3 had high levels of inbreeding (F = 0.79). Agro-morphological trait evaluation further identified significant differences in leaf length, plant weight, and head height across clusters. These findings provide valuable insights into the genetic and phenotypic diversity of lettuce, facilitating the development of more robust breeding programs. Additionally, the core collection established in this study offers a representative subset of the lettuce germplasm for future genomic research and conservation efforts. [ABSTRACT FROM AUTHOR]

We evaluated the effects of neodymium (0.000, 2.885, 5.770 and 8.655 mg · L−1) and zinc (0.1, 0.2 and 0.3 mg · L−1), as well as their interaction on lettuce plants in hydroponics. Applications of 2.885 mg Nd · L−1 and 5.770 mg Nd · L−1 increased plant height, number of leaves and leaf area, as well as fresh and dry stem, root and total biomasses. Root volume was greater in plants treated with 2.885 mg Nd · L−1. With 0.1 mg Zn · L−1, plant height, leaf area and fresh stem, root and total biomass were greater, while applying 0.3 mg Zn · L−1 increased the ratio of dry biomass of stems and roots. Plants exposed to 5.770 mg Nd · L−1 + 0.3 mg Zn · L−1 exhibited greater leaf length. The ratios of fresh and dry biomass of stems and roots increased in plants treated with 8.655 mg · L−1 Nd + 0.3 mg Zn · L−1. Dry biomass weights of stems, roots and total were the highest in plants treated with 20 mg Nd · L−1 + 0.1 mg Zn · L−1. Nd significantly increased foliar concentration of N, P and K. Hence, Nd and Zn improve growth and nutrition. [ABSTRACT FROM AUTHOR]

Herbicides are important for weed control but can severely impact ecosystems, causing soil and water contamination, biodiversity loss, and harm to non-target organisms. Tebuthiuron, widely used in sugarcane cultivation, is highly soluble and persistent, posing significant environmental risks. Microbial inoculation has emerged as a sustainable strategy to mitigate such damage. This study investigated the phytoremediation potential of Mucuna pruriens and Canavalia ensiformis in tebuthiuron-contaminated soils, enhanced by fungal and bacterial inoculants. Crotalaria juncea served as a bioindicator plant, and Lactuca sativa was used in ecotoxicological bioassays. During a 140-day greenhouse experiment from September 2021 to March 2022, M. pruriens showed faster growth than C. ensiformis in uncontaminated soils but was more affected by tebuthiuron. Bacterial inoculants improved M. pruriens growth under stress, while fungal inoculants mitigated tebuthiuron's effects on C. ensiformis. C. juncea exhibited high sensitivity to tebuthiuron but grew beyond 100 cm with bacterial inoculants. Ecotoxicological assays showed that bacterial bioaugmentation significantly reduced soil toxicity. Natural attenuation further decreased tebuthiuron toxicity, and prior cultivation of M. pruriens enhanced soil detoxification. This integrated approach combining phytoremediation and bioaugmentation offers a sustainable method to degrade tebuthiuron, foster safer agriculture, and reduce environmental and health risks. [ABSTRACT FROM AUTHOR]

Pyraclostrobin-based fungicides play an effective role in controlling fungal diseases and are extensively used in agriculture. However, there is concern regarding the potential adverse effects attributed to exposure to these fungicides on non-target organisms and consequent influence exerted on ecosystem functioning. Thus, it is essential to conduct studies with model organisms to determine the impacts of these fungicides on different groups of living organisms. The aim of this study was to examine the ecotoxicity associated with exposure to commercial fungicides containing pyraclostrobin. The focus of the analysis involved germination and initial development of seedlings of 4 plant models (Lactuca sativa, Raphanus sativus, Pennisetum glaucum and Triticum aestivum), in addition to determining the population growth rate and total carbohydrate content in microalga Raphidocelis subcapitata. The fungicide pyraclostrobin adversely influenced growth and development of the tested plants, indicating a toxic effect. The fungicide exerted a significant impact on the initial development of seedlings of all model species examined with T. aestivum plants displaying the greatest susceptibility to pyraclostrobin. Plants of this species exhibited inhibitory effects on both aerial parts and roots when treated with a concentration of 4.75 mg/L pyraclostrobin. In addition, the green microalga R. subcapitata was also significantly affected by the fungicide, especially at relatively high concentrations as evidenced by a reduction in total carbohydrate content. This commercial fungicide demonstrated potential phytotoxicity for the tested plant models and was also considered toxic to the selected microalgae, indicating an ecotoxic effect that might affect other organisms in aquatic environments. [ABSTRACT FROM AUTHOR]

Accurate and non-destructive methods for measuring leaf area are crucial for understanding the growth and physiological variations of plants under stress conditions. This investigation aimed to develop and assess the effectiveness of various regression models for predicting the leaf area of curly lettuce cultivated under different irrigation water salinities (IWS: 0.30, 4.15, 8.0 dS m-1) and salicylic acid doses (SA: 0, 1, 2 mM). The coefficient of determination (R²) values for the models ranged from 0.505 to 0.968, with Root Mean Square Error (RMSE) values between 4.59 and 17.79 cm² and Mean Absolute Error (MAE) values of 3.44 to 13.05 cm². Using only leaf length (LL) and leaf width (LW) can effectively estimate the leaf area of curly lettuce plants (Model 3, R²: 0.962, RMSE: 7.58 cm², MAE: 5.34 cm²). Incorporating IWS and SA into prediction models enhanced their accuracy and reliability. The best model for estimating the leaf area of curly lettuce was found from Model 13, which integrated all four parameters--SA, IWS, LL, and LW--achieving the highest R² (0.968) and the lowest RMSE (4.59 cm²) and MAE (3.44 cm²). Finally, using leaf area prediction models that consider stress conditions can enhance crop management by allowing accurate monitoring of plant health and growth in agriculture. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nanofertilizers and nano-agrochemicals are widely used to increase yield and improve plant growth characteristics in the agricultural field. However, the impact of titanium dioxide nanoparticles (TiO2NPs) on plants growing in humic acid (HA) amended soils has not been investigated before. Therefore, this study aims to determine the effects of TiO2NPs and HA on the growth, yield, and nutritional values of lettuce plants. Lettuce seeds and plants were treated with TiO2NPs suspension (0, 30, and 60 mg/L) and HA solution (0, 3, and 6 g/L) at different concentration levels. The plants were planted in the Randomized Complete Block Design (RCBD) under greenhouse conditions. Overall, TiO2NPs and HA applications improved seed germination rate, plant biomass, and phytochemical contents of the plants. In particular, the integrated TiO2NPs at 30 mg/L and HA at 60 g/L applications significantly increased seed germination (96.49%), plant yield (1123.0 g), and biomass (1159.0 g), as well as antioxidant activity (TAA) (5.25 μg/g FW) and nitrogen (5.08%) contents compared with the control treatment. TiO2NPs and HA applications affected lettuce plant physiology by increasing the plant biomass, as well as biochemical pathways by increasing bioactive compound contents. Interestingly, the phytochemical contents of total polyphenol content (TPC), flavonoid content (TFC), and TAA contents of lettuce plants increased significantly; this indicates that the TiO2NPs and HA applications induce the defense system of the plants. Thus, integrated TiO2NPs and HA applications can be utilized to improve seed germination, growth, yield, and nutritional values of plant species that are nutritionally preferred and also to enhance plant resilience to different environments. [ABSTRACT FROM AUTHOR]

Abstract Background Breeding of lettuce (Lactuca sativa L.), the most important leafy vegetable worldwide, for enhanced disease resistance and resilience relies on multiple wild relatives to provide the necessary genetic diversity. In this study, we constructed a super-pangenome based on four Lactuca species (representing the primary, secondary and tertiary gene pools) and comprising 474 accessions. We include 68 newly sequenced accessions to improve cultivar coverage and add important foundational breeding lines. Results With the super-pangenome we find substantial presence/absence variation (PAV) and copy-number variation (CNV). Functional enrichment analyses of core and variable genes show that transcriptional regulators are conserved whereas disease resistance genes are variable. PAV-genome-wide association studies (GWAS) and CNV-GWAS are largely congruent with single-nucleotide polymorphism (SNP)-GWAS. Importantly, they also identify several major novel quantitative trait loci (QTL) for resistance against Bremia lactucae in variable regions not present in the reference lettuce genome. The usability of the super-pangenome is demonstrated by identifying the likely origin of non-reference resistance loci from the wild relatives Lactuca serriola, Lactuca saligna and Lactuca virosa. Conclusions The super-pangenome offers a broader view on the gene repertoire of lettuce, revealing relevant loci that are not in the reference genome(s). The provided methodology and data provide a strong basis for research into PAVs, CNVs and other variation underlying important biological traits of lettuce and other crops.

Summary Bolting time is an important agronomic trait in lettuce (Lactuca sativa) production. Premature bolting significantly reduces crop quality and marketability. Here, we report map‐based cloning and characterization of a LsKN1 gene that controls bolting in lettuce. A segregating population was developed by crossing a crisphead‐type cultivar with a stem‐type cultivar to genetically map and clone the LsKN1 gene. In the late‐bolting parent (crisphead), the LsKN1 was activated by a CACTA‐like transposon which was inserted into the first exon of LsKN1. Complementation test, overexpression, and CRISPR/cas9 knockout showed that the activated LsKN1 allele (LsKN1TP) delays bolting in lettuce. ChIP‐seq and phytohormone analysis demonstrated that LsKN1 regulates gibberellin (GA) biosynthesis and response. LsKN1TP binds to the promoter of the LsGA20ox1 and LsRGA1, and down‐ and upregulates their expression, respectively. Furthermore, LsRGA1 interacts with LsKN1TP to enhance the repression of GA biosynthesis. LsOFP6 acts as a safeguard, interacting with LsKN1TP to prevent excessive inhibition of GA biosynthesis and response during the vegetative‐to‐reproductive phase transition. The LsKN1‐LsOFP6 module orchestrates the GA pathway to regulate bolting time in lettuce, which provides insight into the bolting development in lettuce and offers valuable genetic resources for breeding lettuce varieties resistant to premature bolting. [ABSTRACT FROM AUTHOR]

Humans have been using plants in the treatment of various diseases for millennia. Currently, even with allopathic medicines available, numerous populations globally still use plants for therapeutic purposes. Although plants constitute a safer alternative compared to synthetic agents, it is well established that medicinal plants might also exert adverse effects. Thus, the present investigation aimed to assess the phytotoxic, cytotoxic, and genotoxic potential of two plants from the Brazilian Cerrado used in popular medicine, Davilla nitida (Vahl) Kubitzki, and Davilla elliptica (A. St.-Hil.). To this end, germination, growth, and cell cycle analyses were conducted using the plant model Lactuca sativa. Seeds and roots were treated with 0.0625 to 1 g/L for 48 hr under controlled conditions. The germination test demonstrated significant phytotoxic effects for both species at the highest concentrations tested, while none of the extracts produced significant effects in the lettuce growth test. In the microscopic analyses, the aneugenic and cytotoxic action of D. elliptica was evident. In the case of D. nitida greater clastogenic action and induction of micronuclei, (MN) were noted suggesting that the damage initiated by exposure to these extracts was not repaired or led to apoptosis. These findings indicated that the observed plant damage was transmitted to the next generation of cells by way of MN. These differences in the action of the two species may not be attributed to qualitative variations in the composition of the extracts as both are similar, but to quantitative differences associated with synergistic and antagonistic interactions between the compounds present in these extracts. [ABSTRACT FROM AUTHOR]

Cigarette butts (CBs) are a major source of persistent pollution in coastal ecosystems, introducing harmful chemicals and microplastics into the environment. This study assesses the ecotoxicological impact of CB leachates on Marbella Beach, Chile, by analyzing the metal contamination and its phytotoxic effects on Lactuca sativa and Lolium perenne. Three scenarios were evaluated: CBs alone, CBs mixed with sand, and sand alone. Leachate analysis revealed significant concentrations of iron and zinc, with higher toxicity observed in scenarios involving CBs. Ecotoxicological assays demonstrated that cigarette butt leachates severely inhibited seed germination and plant growth, particularly in Lactuca sativa, which showed greater sensitivity compared to that of Lolium perenne. The results underscore the partial mitigating role of sand, although it was insufficient to prevent the toxic effects of CBs. The persistence of cellulose acetate in the environment and the continued release of hazardous chemicals highlight the ecological risks posed by cigarette butt pollution. These findings emphasize the need for improved waste management strategies and the development of biodegradable cigarette filters to reduce environmental contamination in coastal areas. [ABSTRACT FROM AUTHOR]

Plants exposed to drought not only have to cope with a shortage of water, but also with a simultaneous decrease in nutrient availability. In this greenhouse experiment, the responses of antioxidants and key metabolites to 2 or 4 days of water limitation immediately prior to harvest were compared to the effect of nutrient limitation with continued water supply in lettuce leaves. Water limitation led to a faster increase in stress intensity than nutrient limitation. While moderate drought stress led to a slight increase in the antioxidant compounds studied, there was a concomitant sharp decrease in starch content. Under nutrient limitation, an increase in the content of ascorbic acid, the proportion of reduced ascorbic acid and the content of phenolic compounds, flavonoids, soluble sugars and starch was observed in the mild phase of stress. These results suggest that reducing nutrient availability shortly before harvest could be a suitable means of improving the nutritional value of crops through cultivation practices as opposed to breeding. [ABSTRACT FROM AUTHOR]

There is a growing demand for herbicides that are more effective than conventional ones yet less harmful to ecosystems. In light of this, this study aimed to synthesize esters from phenols and phenoxyacetic acid, using compounds with known phytotoxic potential as starting materials. Phenoxyacetic acid was first synthesized and then utilized in the synthesis of seven esters through Steglich esterification, employing N,N'-dicyclohexylcarboimide and N,N-dimethylpyridin-4-amine in the presence of phenols (thymol, vanillin, eugenol, carvacrol, guaiacol, p-cresol, and β-naphthol), yielding esters 1–7. All synthesized compounds were characterized using mass spectrometry, 1H, and 13C NMR. These compounds were tested for phytotoxicity to evaluate their effects on the germination and root development of Sorghum bicolor and Lactuca sativa seeds, and for the induction of alterations in the mitotic cycle of meristematic cells of L. sativa roots. Esters 1, 3, 4, and 5 exhibited the most significant phytotoxic activity in both L. sativa and S. bicolor. Alterations in the mitotic index and frequency of chromosomal alterations in L. sativa roots revealed the cytotoxic, genotoxic effects, and the aneugenic mode of action of the tested molecules. These findings suggest that these compounds could serve as inspiration for the synthesis of new semi-synthetic herbicides. [ABSTRACT FROM AUTHOR]

Fusarium wilt, caused by the soilborne fungal pathogen Fusarium oxysporum f. sp. lactucae (FOL), is an economically important disease of lettuce (Lactuca sativa) throughout the world. Four pathogenic races of FOL are reported, though only race 1 is known to exist in the United States. Recently, Californian lettuce growers have expressed increasing concern about Fusarium wilt, as some race 1‐resistant cultivars have exhibited susceptibility, and some susceptible cultivars have displayed reduced disease severity. To determine whether such changes in disease patterns are responses to potentially novel variants, we collected infected plants from commercial fields in the Salinas Valley and Santa Maria regions, isolated the fungus, and conducted a series of pathogenicity tests using a set of FOL race differential cultivars over 2 years (2022 and 2023) in controlled conditions. Pathogenicity tests revealed two new FOL variants that elicited novel disease reaction patterns on the set of differential cultivars that have not been previously described. Isolates Fol621 and Fol621s were less aggressive on race 1‐susceptible Banchu Red Fire, designated Variant‐1. Isolate VSP‐0916 incited severe Fusarium wilt on race 1‐resistant Costa Rica No. 4, designated Variant‐2. Moreover, VSP‐0916 exhibited high aggressiveness and the ability to induce disease in other race 1‐resistant cultivars. This study is the first documentation, to our knowledge, of the occurrence of FOL‐inciting Fusarium wilt on race 1‐resistant lettuce in the United States. Our work provides valuable information critical for the development of Fusarium wilt management strategies, including broad‐spectrum resistance breeding efforts against multiple FOL races. [ABSTRACT FROM AUTHOR]

As vegetables have been growing and space has gathered on the market, there is increasing demand for alternative light sources. This research aimed to evaluate the effects of colored LEDs on the germination and initial growth of lettuce plants, as well as their effects on the antioxidant system. Seeds were germinated in a chamber at 20°C under a 12-hour photoperiod. The light treatment in the first phase consisted of white and colored light-emitting diode (LED) lights (red-V + blue-A) in proportions of 100% V, 80% V + 20% A, 50% V + 50% A, and 80% A + 20% V. The first phase of the experiment consisted of a completely randomized design in a 2x4 factorial scheme (two light conditions and four seed lots) with four replications. The first count, germination, germination speed index (GSI), root length, shoot length, total seedling length, and shoot-to-root ratio were evaluated via image analysis. For the second phase of the experiment, the quantification of antioxidative enzyme activity (SOD, CAT, and APX) was performed to assess whether the light treatments (white LED light, colored LED light, and fluorescent light) caused photooxidative damage in the seedlings. Compared with white LED light, colored LED light improved plant germination and growth by promoting faster radicle protrusion, a greater GSI, a longer total seedling length, and a longer primary root length. The quantification of SOD, CAT, and APX activity indicated that the quality of light used in this work did not cause photooxidative stress in lettuce plants. [ABSTRACT FROM AUTHOR]

Zinc (Zn) is a crucial micronutrient for living beings, yet the restricted availability of micronutrients in soil and the limited effectiveness of existing fertilizers often lead to deficiencies in crops, causing malnutrition in the population. Approximately 17.3% of the world's population suffers from health problems related to inadequate Zn intake. Nanobiofortification of crops is a strategy to mitigate this issue. The 'Parris Island' cultivar of lettuce (Lactuca sativa L.) was grown in 5-liter pots using a mixture of river sand and perlite (80:20 v/v) in a greenhouse environment. This study evaluated the effects of foliar application of zinc oxide nanoparticles (ZnO NPs) at concentrations of 0, 50, 75, and 100 mg L-1. ZnO NPs were applied four times at 15-day intervals. At 60 days post-transplantation, we assessed the fresh biomass, bioactive compound content, and bioaccumulation of Zn in lettuce. Results demonstrated that foliar spraying with 100 mg L-1 ZnO NPs enhanced Zn accumulation and the synthesis of bioactive compounds, thereby improving the nutritional profile of lettuce. Additionally, the 75 mg L-1 application increased fresh biomass by 103.23% compared to the control. This study provides compelling evidence of the potential of ZnO NPs as an effective nanofertilizer and biostimulant, presenting a promising approach to enhance Zn concentration and optimize antioxidant metabolism in lettuce plants. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the evaporation (E) and transpiration (T) components of evapotranspiration (ETc), and the growth parameters of curly lettuce (Lactuca sativa L. cv. Caipira) grown under different irrigation treatments. The study was conducted in a Mediterranean-type plastic greenhouse located in Antalya, Türkiye, in the fall and spring growing seasons of 2020 and 2021, respectively. To assess the impact of water stress on ETc and its components, three different irrigation water levels [ I100 for full irrigation treatment (100%), I66 for 66% (I100×0.66), and I33 for 33% (I100×0.33)] were selected. Planted and unplanted pots were used to measure ETc and E independently. The values obtained from these measurements were used as inputs to calculate the evaporation that occurred in the soil under the crop canopy and plant transpiration. In the present study, T was determined indirectly from the difference of measured evapotranspiration and evaporation and estimated with the modified Hernandez-Suarez model (Te). The modified model for the different irrigation treatments showed high Te estimation performance. Evaporation from the soil in the planted pots (Es) was calculated by considering the canopy cover and soil water content. The study revealed that water stress significantly affected lettuce plant height, root length, cover percentage, leaf area index (LAI), number of leaves, fresh and dry head weights, and root weights (p<0.01). The study also investigated the relationship between Es/ETc , and LAI using an exponential method and established a strong nonlinear relationship in all irrigation treatments (R2>0.90). The modified model developed for different irrigation treatments in Mediterranean-type greenhouses can be used to predict lettuce ETc values with greater precision and to better understand the partitioning of ETc into its constituent components. [ABSTRACT FROM AUTHOR]

Vegetable cultivation holds significant socioeconomic importance, while Bidens pilosa L., a weed with allelopathic effects, can negatively impact seed germination and early development in vegetables. This study aimed to determine the allelopathic potential of B. pilosa on the germination and initial development of lettuce and chicory seeds. Two separate trials were conducted, one with lettuce seeds and the other with chicory seeds. Germination and vigor tests were performed in petri dishes using a completely randomized design, with four concentrations of aqueous extract of Bidens p. (0, 20, 60, and 100%) and five replications, totaling 20 experimental plots. The parameters evaluated included: number of days to start germination, number of days to finish germination, germination percentage, germination speed index, average germination time, root length, and hypocotyl length. The number of days to start germination and the average germination time of lettuce and chicory seeds were greater as the concentration of aqueous extracts of B. pilosa increased. Conversely, with increasing extract concentrations, the germination percentage, germination speed index, root length, and hypocotyl length of lettuce and chicory seedlings were reduced. The aqueous extract of B. pilosa leaves exhibited inhibitory allelopathic activity on the physiology of germination and the development of lettuce and chicory seedlings. [ABSTRACT FROM AUTHOR]

SUMMARY: Accurate quantification of gene and transcript‐specific expression, with the underlying knowledge of precise transcript isoforms, is crucial to understanding many biological processes. Analysis of RNA sequencing data has benefited from the development of alignment‐free algorithms which enhance the precision and speed of expression analysis. However, such algorithms require a reference transcriptome. Here we generate a reference transcript dataset (LsRTDv1) for lettuce (cv. Saladin), combining long‐ and short‐read sequencing with publicly available transcriptome annotations, and filtering to keep only transcripts with high‐confidence splice junctions and transcriptional start and end sites. LsRTDv1 identifies novel genes (mostly long non‐coding RNAs) and increases the number of transcript isoforms per gene in the lettuce genome from 1.4 to 2.7. We show that LsRTDv1 significantly increases the mapping rate of RNA‐seq data from a lettuce time‐series experiment (mock‐ and Botrytis cinerea‐inoculated) and enables detection of genes that are differentially alternatively spliced in response to infection as well as transcript‐specific expression changes. LsRTDv1 is a valuable resource for investigation of transcriptional and alternative splicing regulation in lettuce. Significance Statement: Integrating long‐ and short‐read sequencing data from multiple lettuce tissues and treatments with existing publicly available transcriptome annotations led to the development of LsRTDv1. This is a reference transcript dataset that identifies novel genes and significantly increases the number of transcript isoforms per gene providing a valuable resource for accurate quantification of transcript‐level expression, and hence both transcriptional and post‐transcriptional regulation, in this leafy vegetable crop. [ABSTRACT FROM AUTHOR]

The present investigation highlights the necessity of monitoring some basic physico-chemical water quality indicators and their phytotoxic effect using ecotoxicological bioassays such as "seed germination tests." The phytotoxicity of raw and treated vegetable oil refinery wastewater (VORW) using different treatment processes was assessed through some physiological responses (relative seed germination (RSG), seedling elongation, and germination index (GI)) using Lactuca sativa cultivar. Biotest results of different raw water samples revealed a noticeable correlation between the organic matter content and water phytotoxicity. In fact, VORW showed a very low RSG (17 ± 0.7 to –47 ± 0.58%) and high phytotoxic effects (GI < 50%). The use of coagulation/flocculation (CF) allowed a satisfactory phytotoxicity removal where RSG obtained ranged from 83 ± 1.58 to 90 ± 1.2%. However, the effluent still presents high to moderate phytotoxicity since GI remained below 80% which indicates the presence of toxic elements remaining after CF treatment. When VORW were treated using membrane processes, their phytotoxicity was gradually decreased with the decrease in the membrane pore size. The use of microfiltration membranes (MF), with pore size of 5 µm, 1.2 µm, 0.45 µm, and 0.22 µm, showed RSG values ranged from 37 ± 1.15 to 77 ± 1.68% and GI of less than 80% indicating a moderate to high phytotoxicity. However, the use of ultrafiltration (UF) membranes with molecular weight cut-off (MWCO) of 100 kDa, 30 kDa, and 10 kDa made it possible to achieve an RSG of 100% and an IG exceeding 80% showing that the VORW-treated using UF does not exhibit any phytotoxicity effect. Hence, UF appears to be the most efficient and environmentally friendly technology that could be used for safely treated VORW irrigation purposes compared to CF and MF processes. [ABSTRACT FROM AUTHOR]

The aim of the study was to develop a soil-based cultivation method to grow lettuce indoors for 28 days without the need for irrigation or fertilization, and to investigate their growth and physiological responses in this novel growing substrate. Agar (15 g L− 1) was added to a soil mixture, which comprised potting soil, perlite, fertilizer, and water, to semi-solidify it into a substrate block. Lettuce seeds were sown in the semi-solidified substrate, which was prepared in a custom-made, enclosed container with planting holes in the lid. Three different soil-to-water (SW) ratio (v:v) treatments were used to prepare the soil substrate: SW1:1; SW1:2; SW2:1, and three fertilizer treatments were tested: no fertilizer (control); urea; NPK (15:3:3) fertilizer. Results showed that the semi-solidified soil substrates can be used to successfully grow lettuce for 28 days, however, the extent of their growth varied depending on the soil-water ratio and fertilizer treatment. Lettuce plants grown in the NPK-enriched SW2:1 substrate had significantly higher number of leaves, leaf area, and dry weight compared to all the other treatments. In contrast, the lettuce plants grown without additional fertilizers exhibited poor growth regardless of the soil-water ratio used. In the growing substrates supplemented with urea, the SW1:2 ratio treatment produced lettuces with the lowest leaf number, leaf area, leaf fresh weight, and dry weight. Overall, the chlorophyll a/b ratio and Fv/Fm value of lettuces grown in substrate fertilized with NPK were found to be higher than all the other treatments. The key feature of this cultivation method was the use of agar to semi-solidify the waterlogged soil mixture and transform it into a growing substrate that provided the necessary water and nutrients for plant growth over a 28-day period. The growing substrate developed in this study, which is the first of its kind, can be considered as a new soil-based method of growing lettuce indoors. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) have garnered global attention as emerging contaminants due to their adaptability, durability, and robustness in various ecosystems. Still, studies concerning their combination with heavy metals (HMs), their interactions with soil biota, and how they affect soil physiochemical properties and terrestrial plant systems are limited. Our study was set to investigate the combined effect of HMs (cadmium, arsenic, copper, zinc and lead) contaminated soil of Tongling and different sizes (T1 = 106 µm, T2 = 50 µm, and T3 = 13 µm) of polystyrene microplastics on the soil physiochemical attributes, both bacterial and fungal diversity, compositions, AMF (arbuscular mycorrhizal fungi), plant pathogens in the soil, and their effect on Lactuca sativa by conducting a greenhouse experiment. According to our results, the combination of HMs and polystyrene microplastic (PS-MPs), especially the smaller PS-MPs (T3), was more lethal for the lettuce growth, microbes and soil. The toxicity of combined contaminants directly reduced the physio-biochemical attributes of lettuce, altered the lettuce's antioxidant activity and soil health. T3 at the final point led to a significant increase in bacterial and fungal diversity. In contrast, overall bacterial diversity was higher in the rhizosphere, and fungal diversity was higher in the bulk soil. Moreover, the decrease in MPs size played an important role in decreasing AMF and increasing both bacterial and fungal pathogens, especially in the rhizosphere soil. Functional prediction was found to be significantly different in the control treatment, with larger MPs compared to smaller PS-MPs. Environmental factors also played an important role in the alteration of the microbial community. This study also demonstrated that the varied distribution of microbial populations could be an ecological indicator for tracking the environmental health of soil. Overall, our work showed that the combination of HMs and smaller sizes of MPs was more lethal for the soil biota and lettuce and also raised many questions for further studying the ecological risk of PS-MPs and HMs. [ABSTRACT FROM AUTHOR]

In this study, two commercial products based on the main groups of contemporary biostimulants—a commercial leonardite and a seaweed extract—were tested with the objective of assessing the conditions under which they can enhance lettuce (Lactuca sativa L.) performance, particularly to determine if synergies with conventional fertilization methods can be observed. The experimental protocol was arranged as a factorial design with two factors: organic or mineral fertilization × plant biostimulant. The organic or mineral fertilization factor included five levels: two rates of a nitrogen (N) fertilizer (40 (Nmin40) and 80 (Nmin80) kg ha−1 of N), the same N rates applied as an organic amendment (Norg40 and Norg80), and an unfertilized control (N0). The plant biostimulants used were a commercial leonardite (leonardite) for soil application before planting, a commercial seaweed extract (algae) for foliar application during the growing season, and a control without plant biostimulant. Leonardite significantly increased lettuce dry matter yield (DMY) compared to the control only in the first growing cycle (11.5 and 13.5 g plant−1) and showed no significant interaction with conventional fertilization. It also consistently increased phosphorus (P) levels in the plant tissues. The seaweed extract did not show any effect on the plant, nor did it have any interactions with conventional fertilization regarding DMY. In contrast, with mineral fertilization, lettuce DMY increased from 8.0 and 4.0 g plant−1 (N0) to 22.2 and 12.0 g plant−1 (Nmin80) in the first and second growing cycles, respectively. The response to organic fertilization was lower, yet DMY still increased from 4.0 to 8.1 g plant−1 in the second growing cycle. Generally, this type of plant biostimulant is tested under some form of environmental stress, where it often yields positive results. In this study, the optimal cultivation conditions maintained for the lettuce in the pots likely explain the limited response to the biostimulants. This study suggests that the product labels should more clearly indicate whether they are recommended for general cultivation conditions or specifically for situations where a particular environmental stress can be anticipated. [ABSTRACT FROM AUTHOR]

We did a preliminary investigation of the allelopathic activity of 60 invasive and medicinal plants in Sri Lanka on Lactuca sativa (lettuce) and Raphanus sativus (radish). Out of 60 plants, 14 significantly reduced lettuce seedling lengths than distilled water, and 55 plants reduced radish seedling growth. In consideration of all the parameters tested, Cardiospermum halicacabum and Canarium zeylanicum Blume showed the highest phytotoxicity. C. zeylanicum (family Burseraceae), an endemic plant in Sri Lanka was selected for the isolation of phytotoxic compounds. The whole tree has a distinct fragrance bears edible seeds and has potential health benefits. This plant is used for medicinal purposes and its bark contains 3-hydroxy-12-methoxy-8,11,13-podocarpatrien-3-one and acetyl aleuritolic acid. This is the first report of the aforementioned two compounds from C. zeylanicum. These compounds exhibited phytotoxicity against lettuce. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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

The growth and development of green lettuce plants can be modulated by the prevailing light conditions around them. The aim of this study was to evaluate the effect of ambient light enrichment with different LED light spectra on agronomic characteristics, polyphenol concentration and relative gene expression of enzymes associated with polyphenol formation in 'Levistro' lettuce grown hydroponically in a Nutrient Film Technique (NFT) system for 28 days in a greenhouse. The spectra (blue:green:red:far-red) and red:blue (R:B) ratios obtained by enriching ambient light with Blue (B), White (W), Blue-Red (BR) and Red (R) LED light were B: 47:22:21:10, 0.5:1; W: 30:38:23:9, 0.8:1; BR: 33:15:44:8, 1.3:1 and R: 16:16:60:8, 3.8:1, respectively, and photosynthetically active radiation (PAR) under the different treatments, measured at midday, ranged from 328 to 336 µmoles m−2 s−1. The resulting daily light integral (DLI) was between 9.1 and 9.6 mol m−2 day−1. The photoperiod for all enrichment treatments was 12 h of light. The control was ambient greenhouse light (25:30:30:15; R:B = 1.2:1; PAR = 702 µmoles m−2 s−1; DLI = 16.9 mol m−2 day−1; photoperiod = 14.2 h of light). Fresh weight (FW) and dried weight percentage (DWP) were similar among the enrichment treatments and the control. The leaf number increased significantly under BR and R compared to B lights. The relative index of chlorophyll concentration (RIC) increased as plants grew and was similar among the enrichment treatments and the control. On the other hand, the concentration of chlorogenic acid and chicoric acid increased under BR and B lights, which was consistent with the higher relative expression of the coumarate 3-hydroxylase enzyme gene. In view of the results, it is inferred that half of the PAR or DLI is sufficient to achieve normal growth and development of 'Levistro' lettuce plants, suggesting a more efficient use of light energy under the light enrichment treatments. On the other hand, the blue and combined blue-red lights promoted the accumulation of phenolic compounds in the leaves of 'Levistro' lettuce plants. [ABSTRACT FROM AUTHOR]

O cultivo de hortaliças tem grande importância socioeconômica, e a Bidens pilosa L. é uma planta daninha com efeito alelopático que pode diminuir a germinação de sementes de hortaliças e prejudicar seu desenvolvimento inicial. Com este estudo objetivou-se determinar a potencialidade alelopática de picão-preto sobre a germinação e desenvolvimento inicial de sementes de alface e almeirão. Foram conduzidos dois ensaios separadamente, um com sementes de alface e outro com sementes de almeirão. Os testes de germinação e vigor foram conduzidos em placas de petri e dispostos em delineamento inteiramente casualizado, com quatro concentrações de extrato aquoso de picão-preto (0, 20, 60 e 100%) e cinco repetições, totalizando 20 parcelas experimentais. As características avaliadas foram: número de dias para início de germinação, número de dias para finalizar a germinação, porcentagem de germinação, índice de velocidade de germinação, tempo médio de germinação, comprimento da raiz e do hipocótilo. O número de dias para iniciar a germinação e o tempo médio de germinação de sementes de alface e almeirão foram maiores, à medida que aumentou a concentração de extratos aquosos de picão-preto. Com o aumento das concentrações de extrato, o percentual germinativo, o índice de velocidade de germinação, o comprimento da raiz e do hipocótilo de plântulas de alface e almeirão foram reduzidos. O extrato aquoso de folhas de picão-preto apresentou atividade alelopática inibitória sobre a fisiologia da germinação e o desenvolvimento de plântulas de alface e almeirão.

The purpose of this study was to evaluate the ecotoxicological effects on soils containing associations of the herbicide tebuthiuron (TBT), the insecticide thiamethoxam (TMX), vinasse (VIN), and millet (Pennisetum glaucum) cultivation. We conducted the experiment under greenhouse conditions using a completely randomized design with five replications. Treatments consisted in soil application of tebuthiuron (1000 g ha−1 a. i), thiamethoxam (330 g ha−1 a. i), vinasse (113 m3 ha−1) with or without P. glaucum cultivation. The monitoring extended to 50 days after sowing (DAS) and evaluated the ecotoxicological potential from Lactuca sativa seeds as test-organism. Seed germination and root development determined the germination index (GI) concerning the negative control, which was prepared with water. Thus, P. glaucum highlighted a beneficial influence on soil health, thereby mitigating the ecotoxicological effects of TBT and TMX. Results emphasized the importance of the timing in soil sample collection, where early collections after plant seeding result in higher germination rates and rapid soil health improvements. Furthermore, vinasse reduced the ecotoxicological impact of pesticides and TBT presence presented harmful effects to test-organism. The interaction between P. glaucum growth period and soil sampling had a profound impact on ecotoxicity bioassays, which highlighted the importance of early intervention. Therefore, P. glaucum and vinasse can be valuable components in effective phytoremediation strategies, pointing towards future research and enhancement of approaches for sustainable treatment strategies of agricultural soils with pesticides.

Lettuce is the most highly consumed raw leafy vegetable crop eaten worldwide, making it nutritionally important in spite of its comparatively low nutrient density in relation to other vegetables. However, the perception of bitterness caused by high levels of sesquiterpenoid lactones and comparatively low levels of sweet tasting sugars limits palatability. To assess variation in nutritional and taste-related metabolites we assessed 104 members of a Lactuca sativa cv. Salinas x L. serriola (accession UC96US23) mapping population. Plants were grown in three distinct environments, and untargeted NMR and HPLC were used as a rapid chemotyping method, from which 63 unique Quantitative Trait Loci (QTL) were identified. We were able to identify putative regulatory candidate genes underlying the QTL for fructose on linkage group 9, which accounted for up to 36 % of our population variation, and which was stable across all three growing environments; and for 15-p-hydroxyyphenylacetyllactucin-8-sulfate on linkage group 5 which has previously been identified for its low bitterness, while retaining anti-herbivory field effects. We also identified a candidate gene for flavonoid 3′,5′- hydroxylase underlying a polyphenol QTL on linkage group 5, and two further candidate genes in sugar biosynthesis on linkage groups 2 and 5. Collectively these candidate genes and their associated markers can inform a route for plant breeders to improve the palatability and nutritional value of lettuce in their breeding programmes.

Given the fluctuating availability of natural lighting throughout the year, supplemental light is frequently employed to maintain the optimal daily light integral (DLI) levels necessary for adequate plant growth. However, the use of supplemental light translates into higher operational costs. Recent reports suggest that plants can tolerate a day with low DLI following exposure to a day with high DLI from natural light. This was referred to as the ‘carryover’ effect. In such cases, supplemental lighting may not be necessary, resulting in energy savings. In this study, we determined if plants can withstand such DLI fluctuations over multiple days without compromising plant growth. Additionally, we calculated the energy requirements for trese treatments to evaluate the potential energy savings of the carryover effect. To test this, we cultivated lettuce plants (Lactuca sativa cv. ‘Waldmand’s Dark Green’ and ‘Rouxai’) in a walk-in grow chamber, subjecting them to six different lighting treatments. Each treatment consisted of a day with a high DLI of 22.5 mol·m-2·d-1 followed by a varying number of consecutive days with low DLI, ranging from 1 to 5 days, with DLIs of 7.5, 11.25, 12.5, 13.13, and 13.5 mol·m-2·d-1 respectively. The combined DLI for each treatment, calculated as the average DLI across high and low DLI days, was maintained at 15 mol·m-2·d-1. Additionally, we included a control treatment where plants were exposed to a constant DLI of 15 mol·m-2·d-1. We measured plant growth rate, final fresh and dry weights, leaf number, leaf area, specific leaf area, light use efficiency, and relative pigment content to assess differences in plant growth under the different lighting regimes. We observed a decrease in biomass accumulation, as indicated by a 13% reduction in final dry weight only for the treatment involving one day of high DLI followed by one day of low DLI, compared to our control. We discovered that plants can tolerate multiple days of low DLI following a day with high DLI, in contrast to the optimal values reported in the literature. This finding can lead to reduced energy consumption for supplemental lighting and consequent operational cost savings.

In order to create better conditions to achieve food safety and sovereignty, agroecology, as a science, looks for solutions for several steps of the technical itineraries of the crops. Crop nutrition and protection are two main crop itinerary components that have been in the center of farmers challenges and consumers concerns, and biopreparations, which have been prepared using natural substances, have been used in agroecological systems, most times based on farmers empirical knowledge. Six biopreparations—purslane vinegar, prickly pear vinegar, orange fermented fruit juice, garlic extract, nettle infusion, and horsetail decoction—were used in this study, for physicochemical analyses and field tests in two different locations (Viseu and Castelo Branco, Portugal) in nurseries of Lactuca sativa L. (lettuce), and aimed to validate its results and uses. The nettle infusion presented the best stimulating results for the length of aerial part and the garlic extract presented the best results for the length of root, though there weren't significant differences and effects when compared with the control. The results indicate that the biopreparations used did not exert a biostimulant action in relation to the application of water in lettuce nurseries and that more research is needed to confirm the results observed by farmers.

The effects of additional far-red light (FRL) on the photosynthetic and growth parameters of Lactuca sativa plants grown for 30 d and on the photosynthetic activity of the plants under high irradiance [4 h; 1,500 μmol(photon) m-2 s-1] were studied. The plants were grown under coloured light-emitting diodes at a ratio of red light (RL): blue light (BL): green light (GL): far-red light (FRL) = 0.7:1:0.3:0.4 or RL:BL:GL:FRL = 0.7:1:0.3:0.8 (test, T). Additional FRL led to an increase in plant biomass, height, and leaf area but to a decrease in photosynthesis and respiration rates. However, PSII activity was greater in plants with additional FRL. It is suggested that the increase in biomass occurred mainly due to an increase in leaf area but not in photosynthesis. In addition, PSII in the experiment was less resistant to high irradiance. The possible direct and indirect influences of the FRL on growth and photosynthesis were considered.

We investigated the growth dynamics of hydroponic lettuce (Lactuca sativa) driven by the influence that potassium (K+) has on crop growth. This study aimed to determine whether increased K+ concentrations under different daily light integrals (DLIs) in a hydroponic system will boost growth of greenhouse lettuce. This study was conducted within a controlled glass greenhouse environment with varying DLIs achieved by integrating an adaptive lighting control system over a 16-hour photoperiod. We used three K+ treatments of 200, 400, or 600 mg·L-1 K+ and six DLI lighting treatments of 11.1, 12.9, 14.6, 15.9, 16.9, and 17 mol·m-2·d-1. We found that increasing K+ did not increase shoot dry weight, leaf area, or specific leaf area with increasing DLIs. Although K+ and DLI had an interacting effect on the root dry weight fraction, leaf chlorophyll content, and quantum yield of photosystem II, the K+ treatments did not increase or decrease with increasing DLIs. The influencing factor was DLI, which led to increases in shoot dry weight and leaf area, whereas a decrease in specific leaf area was observed with increasing DLIs. Ultimately, adding supplemental concentrations of K+ did not enhance lettuce growth, nor did these effects show any increase with increasing DLIs. [ABSTRACT FROM AUTHOR]

Highlights: The spectral characteristics of different types of white LEDs differ significantly. The Phyto-LED spectrum increases the productivity of lettuce plants The combination of white LEDs and Phyto-LEDs had the same effect on the productivity of lettuce plants as the Phyto-LEDs alone. The combination of white LEDs and Phyto-LEDs has a significantly greater effect on color rendering than does the use of sole Phyto-LED spectrum Phyto-LEDs provoke flowering of lettuce plants The effect of light of various spectral compositions on the complex morphophysiological parameters of lettuce plants in hydroponic was studied. The light sources had the following light spectra: warm white light—2700 K, cold white light—6500 K, and Phyto-LED light, as well as 2700 K + Phyto-LED and 6500 K + Phyto-LED. The dry and fresh biomass, leaf area, stem length, photosynthetic pigment content, photosynthesis and transpiration rates, chlorophyll fluorescence parameters, and percentage of plants that passed into the generative stage of development were studied. The results showed that partial and complete replacement of white LEDs by Phyto-LEDs with lower green light content and greater amounts of far-red light in the radiation spectrum caused an increase in plant productivity of 37%, average leaf area, and transpiration rate in the treatments but also promoted an earlier transition of plants to flowering under light treatment, Phyto-LEDs, and Phyto-LEDs + white LEDs. The 2700 K + Phyto-LED treatment had one of the highest productivities, as did the Phyto-LED and 6500 K + Phyto-LED treatments, but this lighting treatment provoked less flowering on the 60th day of the growing period. [ABSTRACT FROM AUTHOR]

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Adding far-red (FR, 700–800 nm) light to photosynthetic active radiation (400–700 nm) proved to be a possible approach to increasing plant biomass accumulation for lettuce production in indoor vertical farms with artificial lighting as a sole-source lighting. However, how FR light addition influences plant growth, development, and metabolic processes and the optimal value of FR photon flux density for greenhouse-grown lettuce under sunlight are still unclear. This work aims to quantify the value of supplementary FR light with different intensities on lettuce morphological and physiological characteristics in a greenhouse. Lettuce 'Dasusheng' (Lactuca sativa L.) was grown in a greenhouse under seven light treatments, including white plus red LEDs with FR photon flux density at 0, 10, 30, 50, 70, and 90 µmol m−2 s−1 (WR, WR + FR10, WR + FR30, WR + FR50, WR + FR70, and WR + FR90, respectively), and lettuce grown with sunlight only was marked as natural light (NL). FR light addition improved the electron transport flux per cross section and performance index (PIabs, PItotal) and decreased the changes in relative variable fluorescence of lettuce leaves compared to plants under NL. Specifically, the PIabs of lettuce leaves were 41%, 41%, 38%, 33%, 26%, and 25% lower under control than in plants under treatments WR + FR90, WR + FR70, WR + FR50, WR + FR30, WR + FR10, and WR, respectively. Leaf number, leaf area, and biomass accumulation of lettuce followed a quadratic function with increasing FR light intensity and were the highest under treatment WR + FR50. The shoot fresh weight and dry weight of lettuce were increased by 111% and 275%, respectively, under treatment WR + FR50 compared to NL. The contents of vitamin C, reducing sugar, total soluble sugar, and starch in lettuce showed a similar trend with biomass accumulation. In conclusion, with commonly used photosynthetic photon flux density (PPFD, 400–700 nm) around 200 μmol m−2 s−1, supplementary FR light intensity of 30~50 μmol m−2 s−1 was suggested to enhance the photochemistry efficiency, biomass accumulation, and carbohydrates' contents in greenhouse-grown lettuce. [ABSTRACT FROM AUTHOR]

Light/dark (L/D) cycle plays a crucial role in controlling the production and quality of vegetables. However, the mechanism of L/D cycle on vegetable growth and quality is scarce studied. To investigate the impact of L/D cycle on lettuce growth and quality, we designed three diel scenarios, including 16 hours of light and 8 hours of darkness (L16/D8), 12 hours of light and 6 hours of darkness (L12/D6), and 8 hours of light and 4 hours of darkness (L8/D4). By phenotypic analysis, we found that lettuce grew taller under the L8/D4 scenario than under L16/D8 light cycle scenarios. The physiological indexes showed that the lettuce leaves grown in the L8/D4 scenario exhibited greater enhancements in the levels of soluble protein, soluble sugar, and carotenoid content compared to the other scenarios. By comparing the expression levels under different diel scenarios (L16/D8 vs L12/ D6, L16/D8 vs L8/D4, and L12/D6 vs L8/D4), we identified 7,209 differentially expressed genes (DEGs). Additionally, 3 gene modules that were closely related to L/D cycle of lettuce were selected by WGCNA analysis. The eigengenes of three gene modules were enriched in plant hormone signal transduction, sphingolipid metabolism, and nucleocytoplasmic transport pathways. Through network analysis, we identified six hub genes (CIP1, SCL34, ROPGEF1, ACD6, CcmB, and Rps4) in the three gene modules, which were dominant in plant circadian rhythms and greatly affected lettuce growth. qRT-PCR analysis confirmed the diurnal response patterns of the 6 hub genes in different treatments were significant. This study intensively enhanced our comprehension of the L/D cycle in the growth morphology, nutritional quality, and metabolic pathways of lettuce. [ABSTRACT FROM AUTHOR]