Over-expression of LsEXPA6, a lettuce expansin gene, improves cadmium stress tolerance in transgenic Arabidopsis.

Cadmium (Cd) is a harmful heavy metal that is highly toxic to plants and animals. Expansins are cell wall proteins inducing cell wall loosening and participate in all plant growth and development processes which are associated with cell wall modifications. We investigated lettuce's expansin gene LsEXPA6 and found that LsEXPA6 overexpression Arabidopsis lines were much more resistant to cadmium stress. Our results revealed that the root system of the expa6 mutant was suppressed under cadmium stress, resulting in shorter plant height, reduced biomass, and a significant increase in cadmium content in the plants compared with wild-type plants, whereas LsEXPA6 overexpression lines had a well-developed root system and reduced cadmium accumulation in the roots and shoots of the plants. The above results indicated that overexpression of LsEXPA6 affected root development and reduced Cd absorption in Arabidopsis. In addition, the higher absorption capacity of nutrients, increased antioxidant enzymes activities, improved chlorophyll and photosynthetic function in the overexpression Arabidopsis plants, supported the Cd stress tolerance mechanism. Taken together, these results provided a new insight on the role of expansin proteins in the tolerance of plants to Cd stress by root cell elongation.

Biochar amendment affects the fate of phthalic acid esters in the soil-vegetable system.

Phthalates, e.g., esters of phthalic acid (PAEs), when used as plasticizers due to weak physical bonding with polymer matrix favoring leaching, are widely noted in the environment. Their confirmed toxicity to plants and animals implies that their fate should be monitored in the environment, especially when considering the interaction between soil and vegetables. Removal of PAEs from the environment or limiting their bioavailability is a key point in reducing their harmful effects. In the present paper, the fate of six PAEs in the biochar-amended soil during the cultivation of two popular vegetables, lettuce, and radish, was estimated. High bioaccumulation in the soil was noted with the biochar obtained from residues from biogas production being up to 15% higher than in the case of the other biochar and up to 10 times higher than in plants due to increased basic character of biochar. This biochar reduced the bioavailability of DEP (diethyl phthalate), DBP (dibutyl phthalate), BBP (butyl benzyl phthalate), and DNOP (di-n-octyl phthalate) in radish roots and DBP in lettuce leaves. However, PAEs significantly increased the fresh mass of radish and slightly increased the mass of lettuce. All six tested PAEs in both plants reached higher concentrations in the leaves (up to two orders of magnitude) than in the roots. Additionally, PAEs were present in two times higher concentrations in the lettuce than in the radish. The biochar aromaticity, porosity, and the presence of organic carbon and inorganics (ash) affect the fate of tested pollutants depending on the tested plant and compound.

Phytotoxic and Cytogenetic Assessment of Glycerol Triazole Derivatives in Model Plants and Weeds.

Weed invasion represents a challenge for farmers, who typically manage it with herbicides. However, this approach raises concerns about environmental and human health, as well as increasing resistance in these plants with continued use. Therefore, exploring alternative methods, such as heterocyclic compounds, triazoles, is essential due to their biological and environmental relevance. This study aimed to evaluate the effects of twelve 1,2,3-triazoles on the germination and early development of Lactuca sativa, Bidens pilosa, and Lolium multiflorum, as well as their impact on cell division in the cells of L. sativa. Triazole derivatives 4a, 4b, 4c, 4g, 4h, 4i, 4k, and 4l exhibited phytotoxicity, showing varying levels of inhibition in germination, germination speed index, and root growth. Chlorinated compounds were the most detrimental to lettuce development. B. pilosa was notably affected by compounds 4h, 4i, 4k, and 4l, while L. multiflorum responded most to triazoles 4c and 4l, with effectiveness comparable to that of the herbicide glyphosate. All derivatives, except 4l, exhibited aneugenic mechanisms of action, and 4a, 4b, 4c, 4e, 4f, and 4g showed clastogenic effects. This study demonstrated the potential of triazoles as effective agents against weed growth, with mechanisms that warrant further investigation for agricultural applications.

Isolation and characterization of pathogenic Klebsiella pneumoniae strains from lettuce: a potential source of antibiotic resistance and development of a mathematical model for ANOVA results.

Introduction: This study aimed to evaluate the prevalence of Klebsiella pneumoniae contamination in raw lettuce from Risalpur, Pakistan, and to analyze the antibiotic susceptibility profiles of the isolated strains. The presence of foodborne pathogens such as K. pneumoniae poses significant public health risks, particularly in regions with suboptimal hygiene practices and improper food handling. Methods: Lettuce samples were collected from various sources in Risalpur and screened for K. pneumoniae. Antimicrobial susceptibility testing was performed to evaluate the effectiveness of various antibiotics against the isolated strains. Statistical analyses, including ANOVA and linear regression, were conducted to assess differences in inhibition zones and to predict antibiotic effectiveness based on concentration. Results: The results revealed a significant prevalence of K. pneumoniae in the lettuce samples, highlighting the risks associated with poor hygiene, transportation, storage, and contaminated irrigation water. The isolated strains exhibited high susceptibility to gentamicin but demonstrated notable resistance to doxycycline, vancomycin, and ticarcillin. Multidrug-resistant (MDR) strains were identified. ANOVA showed significant differences in inhibition zones, and the linear regression model predicted a Zone of Inhibition based on antibiotic concentration (ß0 = 10.6667, ß1 = 0.4556). Discussion: The identification of MDR strains of K. pneumoniae underscores the urgent need for enhanced antibiotic stewardship and food safety protocols to manage foodborne pathogens. Improved hygiene practices throughout the food production and supply chain are critical to mitigate health risks and address the challenge of growing antibiotic resistance.

Spent coffee grounds as an alternative fertilizer: impact on bioaccessibility of antioxidants and commercial quality of lettuce.

BACKGROUND: During the processing of spent coffee grounds (SCGs) several residues are obtained, which are mostly disposed of in landfills. There is an urgent need for a comprehensive waste management strategy for these residues. This study evaluates the potential of SCGs as a biofertilizer by assessing their effects on lettuce leaves and the release of antioxidants following in vitro digestion and fermentation. RESULTS: Lettuce plants were grown with different amounts of SCGs (0-150 g kg-1) in the substrate. High SCG concentrations in the soil generated lighter colored tissues, a decrease in the green color, less root development, and lower dry weight of leaves (P < 0.05). The SCG levels also affected the release of antioxidants by the final product. This effect was more pronounced in the digested fraction: applying the Ferric Reducing Antioxidant Power (FRAP) method, the addition of SCGs from 10 g kg-1 to 125 g kg-1 increased the amount of antioxidant from 43.88 ± 4.81 to 105.96 ± 29.09 µmol Trolox g-1 of dry weight (P < 0.05). The Indigo Carmine Reducing Capacity (ICRED) method also showed a similar trend, but in this case the highest value was obtained with 150 g kg-1 of SCGs (16.41 ± 3.93 mmol catechin g-1 of dry weight) (P < 0.05). Moreover, in the fermented fraction a significant increase in the antioxidant released was found with low levels of SCG(P<0.05), while lettuces fertilized with intermediate amounts of SCGs (25 and 50 g kg-1) presented the highest amount of insoluble antioxidant (P < 0.05). CONCLUSION: A compromise should be found in order to achieve a product with a high antioxidant capacity and an acceptable visual quality. © 2024 Society of Chemical Industry.

Comparative genomics and transcriptomics reveal differences in effector complement and expression between races of Fusarium oxysporum f.sp. lactucae.

This study presents the first genome and transcriptome analyses for Fusarium oxysporum f. sp. lactucae (Fola) which causes Fusarium wilt disease of lettuce. Long-read genome sequencing of three race 1 (Fola1) and three race 4 (Fola4) isolates revealed key differences in putative effector complement between races and with other F. oxysporum ff. spp. following mimp-based bioinformatic analyses. Notably, homologues of Secreted in Xylem (SIX) genes, also present in many other F. oxysporum ff. spp, were identified in Fola, with both SIX9 and SIX14 (multiple copies with sequence variants) present in both Fola1 and Fola4. All Fola4 isolates also contained an additional single copy of SIX8. RNAseq of lettuce following infection with Fola1 and Fola4 isolates identified highly expressed effectors, some of which were homologues of those reported in other F. oxysporum ff. spp. including several in F. oxysporum f. sp. apii. Although SIX8, SIX9 and SIX14 were all highly expressed in Fola4, of the two SIX genes present in Fola1, only SIX9 was expressed as further analysis revealed that SIX14 gene copies were disrupted by insertion of a transposable element. Two variants of Fola4 were also identified based on different genome and effector-based analyses. This included two different SIX8 sequence variants which were divergently transcribed from a shared promoter with either PSE1 or PSL1 respectively. In addition, there was evidence of two independent instances of HCT in the different Fola4 variants. The involvement of helitrons in Fola genome rearrangement and gene expression is discussed.

Food waste biochar for sustainable agricultural use: Effects on soil enzymes, microbial community, lettuce, and earthworms.

This study investigates the effects of food waste biochar (FWB) on the biological properties of soil, including the microbial community structure, enzyme activities, lettuce growth, and earthworm ecotoxicity. This holistic assessment of various soil organisms was used to assess the potential of FWB as a soil amendment strategy. Pot experiments were carried out over a 28-d period using various FWB concentrations in soil (0-3% w/w). The presence of FWB enhanced the activity of alkaline phosphatase and beta-glucosidase in proportion to the FWB concentration. Similarly, the dehydrogenase activity after 28 d was positively correlated with the FWB concentration. Notably, the application of FWB improved the bacterial diversity in the soil, particularly among hydrocarbonoclastic bacteria, while also prompting a shift in the fungal community structure at the class level. Measures of lettuce growth, including total fresh weight, shoot length, and leaf number, also generally improved with the addition of FWB, particularly at higher concentrations. Importantly, FWB did not adversely affect the survival or weight of earthworms. Collectively, these findings suggest that FWB can enhance soil microbial enzyme activity and support plant growth-promoting rhizobacteria, potentially leading to increased crop yields. This highlights the potential of FWB as an eco-friendly soil amendment strategy.

Hydroponic lettuce in-situ water circulation evaluation via nondestructive mass measurement in controlled environment.

This study proposed a hydroponic system with the capacity to acquire high-resolution in situ mass data for non-destructive evaluation of water circulation in lettuce. The system customizes the watering profile, enables high-frequency in situ weight measurement, and monitors multidimensional environment changes. Key air, water, and light parameters were collected to evaluate the plant response, susceptibility, and adaptability to environmental conditions. Multiple physiological indices were defined to characterize the properties of two lettuce varieties in response to different environmental factors.

Lactuca super-pangenome reduces bias towards reference genes in lettuce research.

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.

Toxicity of paclobutrazol-based pesticide on Lactuca sativa L.: germination, seedling development, and DNA damage.

Paclobutrazol, a fungicide of the triazole class, is widely used as an inducer of early flowering and fruiting by inhibiting gibberellin formation. However, biological assays using model organisms to evaluate their cytogenotoxic and mutagenic potential are still scarce. Therefore, this study aimed to investigate the effects of the commercial product Cultar® 250 SC (CP) and the pure substance (PBZ) on the germination and initial seedling development of Lactuca sativa L. (lettuce), in addition to evaluating the effects of CP on the mitotic activity and DNA, as we believe that PBZ has a greater toxic potential than CP on seed germination, and that the latter has cytogenotoxic and mutagenic effects on L. sativa. Lettuce seeds treated with CP and with PBZ in the doses of 0.25, 0.50, 1, 1.5, and 2 g L-1 showed significant reductions in germination rate, as well the CP reduced the root and initial development seedling development. PBZ showed greater inhibition of germination compared to CP. In direct exposure to PBZ, there was not sufficient seedling development for analysis, while in discontinuous treatment, there was inhibition of root growth (except for doses of 0.25 and 0.50 g L-1) and in the development of the aerial part. While no mitodepressive effect was observed in meristematic cells treated with CP, increased frequencies of chromosomal alterations, including condensed nuclei and micronuclei, were evident in both meristematic cells and the F1 region. The Comet assay further demonstrated higher levels of DNA damage at higher paclobutrazol doses, supporting the findings of increased micronucleus frequencies. Consequently, it can be concluded that the CP exhibits greater toxicity towards seed germination compared to lettuce seedlings, and PBZ has a greater toxic potential than CP in relation to these parameters. However, the impact of CP on seedlings was relatively minimal, as evidenced by their limited effects on development, cell proliferation, and DNA, suggesting a slight toxicity of this agent. Therefore, we infer that Cultar® 250 SC should be used with caution. Thus, this study emphasizes the importance of employing joint analyses to better elucidate and correlate the mechanisms of action of potentially toxic substances. Furthermore, it provides a basis for discussing the application of Cultar® 250 SC and seeking more sustainable alternatives in food production.

Oilseed Cakes: A Promising Source of Antioxidant, and Anti-Inflammatory Agents-Insights from Lactuca sativa.

This study evaluated the antioxidant and antibacterial properties of methanolic extracts derived from oilseed cakes of Lactuca sativa (lettuce), Nigella sativa (black seed), Eruca sativa (rocket), and Linum usitatissimum (linseed). Lettuce methanolic extract showed the highest potential, so it was selected for further investigation. High-performance liquid chromatography (HPLC-DAD) analysis and bioassay-guided fractionation of lettuce seed cake extract led to the isolation of five compounds: 1,3-propanediol-2-amino-1-(3',4'-methylenedioxyphenyl) (1), luteolin (2), luteolin-7-O-ß-D-glucoside (3), apigenin-7-O-ß-D-glucoside (4), and ß-sitosterol 3-O-ß-D-glucoside (5). Compound (1) was identified from Lactuca species for the first time, with high yield. The cytotoxic effects of the isolated compounds were tested on liver (HepG2) and breast (MCF-7) cancer cell lines, compared to normal cells (WI-38). Compounds (2), (3), and (4) exhibited strong activity in all assays, while compound (1) showed weak antioxidant, antimicrobial, and cytotoxic effects. The anti-inflammatory activity of lettuce seed cake extract and compound (1) was evaluated in vivo using a carrageenan-induced paw oedema model. Compound (1) and its combination with ibuprofen significantly reduced paw oedema, lowered inflammatory mediators (IL-1ß, TNF-α, PGE2), and restored antioxidant enzyme activity. Additionally, compound (1) showed promising COX-1 and COX-2 inhibition in an in vitro enzymatic anti-inflammatory assay, with IC50 values of 17.31 ± 0.65 and 4.814 ± 0.24, respectively. Molecular docking revealed unique interactions of compound (1) with COX-1 and COX-2, suggesting the potential for targeted inhibition. These findings underscore the value of oilseed cakes as a source of bioactive compounds that merit further investigation.

GC-MS metabolomics of French lettuce (Lactuca Sativa L. var capitata) leaves exposed to bisphenol A via the hydroponic media.

INTRODUCTION: Bisphenol A (BPA), an organic compound used to produce polycarbonate plastics and epoxy resins, has become a ubiquitous contaminant due to its high-volume production and constant release to the environment. Plant metabolomics can trace the stress effects induced by environmental contaminants to the variation of specific metabolites, making it an alternative way to study pollutants toxicity to plants. Nevertheless, there is an important knowledge gap in metabolomics applications in this area. OBJECTIVE: Evaluate the influence of BPA in French lettuce (Lactuca Sativa L. var capitata) leaves metabolic profile by gas chromatography coupled to mass spectrometry (GC-MS) using a hydroponic system. METHODS: Lettuces were cultivated in the laboratory to minimize biological variation and were analyzed 55 days after sowing (considered the plant's adult stage). Hexanoic and methanolic extracts with and without derivatization were prepared for each sample and analyzed by GC-MS. RESULTS: The highest number of metabolites was obtained from the hexanoic extract, followed by the derivatized methanolic extract. Although no physical differences were observed between control and contaminated lettuce leaves, the multivariate analysis determined a statistically significant difference between their metabolic profiles. Pathway analysis of the most affected metabolites showed that galactose metabolism, starch and fructose metabolism and steroid biosynthesis were significantly affected by BPA exposure. CONCLUSIONS: The preparation of different extracts from the same sample permitted the determination of metabolites with different physicochemical properties. BPA alters the leaves energy and membrane metabolism, plant growth could be affected at higher concentrations and exposition times.

Response of crop seed germination and primary root elongation to a binary mixture of diclofenac and naproxen.

Non-steroidal anti-inflammatory drugs, diclofenac (DCF) and naproxen (NPX), represent a group of environmental contaminants often detected in various water and soil samples. This work aimed to assess possible phytotoxic effects of DCF and NPX in concentrations 0.1, 1 and 10 mg/L, both individually and in binary mixtures, on the seed germination and primary root elongation of crops, monocots Allium porrum and Zea mays, and dicots Lactuca sativa and Pisum sativum. Results proved that the seed germination was affected by neither individual drugs nor their mixture. The response of primary root length in monocot and dicot species to the same treatment was different. The Inhibition index (%) comparing the root length of drug-treated plants to controls proved to be approximately 10% inhibition in the case of dicots lettuce and pea, and nearly 20% inhibition in monocot leek, but almost 20% stimulation in monocot maize. Assessment of the binary mixture effect confirmed neither synergistic nor antagonistic interaction of DCF and NPX on early plant development in the applied concentration range.

Silencing of RDR1 and RDR6 genes by a single RNAi enhances lettuce's capacity to express recombinant proteins in transient assays.

KEY MESSAGE: Enhanced recombinant protein expression was achieved in Salinas lettuce and commercial lettuce by designing a unique RNAi that knockdown the gene-silencing mechanism in transient assays. Improved yields of recombinant proteins (RP) are necessary for protein-production efficiency and ease of purification. Achieving high yield in non-tobacco plants will enable diverse plants to be used as hosts in transient protein-expression systems. With improved protein yield, lettuce (Lactuca sativa) could take the lead as a plant host for RP production. Therefore, this study aimed to improve RP production in lettuce var. Salinas by designing a single RNA interference (RNAi) construct targeting LsRDR1 and LsRDR6 using the Tsukuba system vector. Two RNAi constructs, RNAi-1 and RNAi-2, targeting common regions of LsRDR1 and LsRDR6 with 75% and 76% similarity, respectively, were employed to evaluate simultaneous gene silencing. Quantitative transcription analysis demonstrated that both RNAi constructs effectively knocked down LsRDR6 and LsRDR1, but not LsRDR2, at both 3 and 5 days post-infiltration (dpi), with RNAi-1 exhibited slightly higher efficiency. Based on the protein yield, co-expression of RNAi-1 with enhanced green fluorescent protein (EGFP) increased EGFP expression by approximately 4.9-fold and 3.7-fold at 3 dpi and 5 dpi, respectively, compared to control. A similar but slightly lower increase (2.4-fold and 2.33-fold) was observed in commercial lettuce at 3 and 5 dpi, respectively. To confirm these results, co-infiltration with Bet v 1, a major allergen from birch pollen, resulted in a 2.5-fold increase in expression in Salinas lettuce at 5 dpi. This study marks a significant advancement in enhancing transient protein production in lettuce, elevating its potential as a host for recombinant protein production.

Agricultural Mitigation Strategies to Reduce the Impact of Romaine Lettuce Contamination.

BACKGROUND: Leafy greens, particularly romaine lettuce, are often associated with outbreaks due to their susceptibility to contamination from various environmental sources. This study aimed to evaluate the presence of E. coli, Salmonella, copper, nickel, zinc, and manganese in irrigation water, lettuce leaves, and agricultural soil in the Litani River Basin (LRB), Lebanon. METHOD: Samples were collected from five demonstration plots employing different agricultural practices. Heavy metal concentrations were determined using atomic absorption spectrometry, while E. coli and Salmonella testing were conducted through conventional culturing techniques. The impact of E. coli contamination on seed germination and the interaction effects between E. coli and heavy metals were also examined. The study also compared the effectiveness of various irrigation systems in reducing bacterial contamination. RESULTS: The results demonstrated that contamination levels varied significantly across the plots and irrigation types. This variation underscores the necessity of site-specific mitigation strategies to enhance food safety. Our findings highlight the importance of selecting appropriate irrigation methods and implementing tailored agricultural practices to minimize the risk of contamination. CONCLUSION: This research provides valuable insights for optimizing agricultural practices in the LRB to ensure food safety and environmental sustainability.

A comparison of the biofouling potential of field-collected and laboratory-cultured Ulva.

The marine algae Ulva spp. are commonly used as model biofouling organisms. As biofouling studies are primarily conducted using field-collected specimens, factors including species identity, seasonal availability, and physiological status can hinder the replicability of the results. To address these limitations, a protocol was developed for the on-demand laboratory culture and release of Ulva zoospores. The biofouling potential of laboratory-cultured and field-collected Ulva blades was compared using a waterjet. No significant differences were found between field and laboratory-cultured samples in either spore adhesion (before waterjet) or the proportion of spores retained after waterjet exposure. However, there was significant variability within each session type in pre- and post-waterjet exposures, indicating that spore adhesion and retention levels vary significantly among trial runs. In addition, all our laboratory cultures were Ulva Clade C (LPP complex). In contrast, our field samples contained a mix of Ulva Clade C, U. compressa clade I, and U. flexuosa Clade D. This protocol for on-demand production of Ulva spores can improve biofouling research approaches, enables comparison of results across laboratories and regions, and accelerate the development of anti-biofouling strategies.

Rapid detection of Impatiens necrotic spot virus from thrips vectors using reverse transcription-recombinase polymerase amplification.

The plant virus, Impatiens necrotic spot virus (INSV), is an economically important pathogen of vegetables, fruits, and ornamental crops. INSV is vectored by the western flower thrips, Frankliniella occidentalis, a small insect pest that is globally distributed. In recent years, INSV outbreaks have reached epidemic levels in the Salinas Valley of California-an agriculturally rich region where most of the lettuce (Lactuca sativa) is produced in the United States. Due to the obligate nature in which virus transmission occurs, new tools that could rapidly detect INSV from thrips vectors would enhance our ability to predict where virus outbreaks may occur. Here, we report on the development of a reverse transcription-recombinase polymerase amplification (RT-RPA) assay that can detect INSV from individual thrips. The assay uses crude extraction methods, is performed at a single temperature of 42 °C, can be completed in 25 min, and provides sensitivity levels that are comparable to other available detection methods. When the assay was used on field populations of thrips, INSV was successfully identified and quantified from individual larvae and adults. The work provides a new cost-effective surveillance tool that can rapidly detect INSV from its insect vector and from plants.

Investigating the influence of varied ratios of red and far-red light on lettuce (Lactuca sativa): effects on growth, photosynthetic characteristics and chlorophyll fluorescence.

Far red photon flux accelerates photosynthetic electron transfer rates through photosynthetic pigments, influencing various biological processes. In this study, we investigated the impact of differing red and far-red light ratios on plant growth using LED lamps with different wavelengths and Ca1.8Mg1.2Al2Ge3O12:0.03Cr3+ phosphor materials. The control group (CK) consisted of a plant growth special lamp with 450 nm blue light + 650 nm red light. Four treatments were established: F1 (650 nm red light), F2 (CK + 730 nm far-red light in a 3:2 ratio), F3 (650 nm red light + 730 nm far-red light in a 3:2 ratio), and F4 (CK + phosphor-converted far-red LED in a 3:2 ratio). The study assessed changes in red and far-red light ratios and their impact on the growth morphology, photosynthetic characteristics, fluorescence characteristics, stomatal status, and nutritional quality of cream lettuce. The results revealed that the F3 light treatment exhibited superior growth characteristics and quality compared to the CK treatment. Notably, leaf area, aboveground fresh weight, vitamin C content, and total soluble sugar significantly increased. Additionally, the addition of far-red light resulted in an increase in stomatal density and size, and the F3 treatments were accompanied by increases in net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci), and stomatal conductance (Gs). The results demonstrated that the F3 treatment, with its optimal red-to-far-red light ratio, promoted plant growth and photosynthetic characteristics. This indicates its suitability for supplementing artificial light sources in plant factories and greenhouses.

Toxic and non-toxic cyanobacterial biomass as a resource for sustainable agriculture: A lettuce cultivation experiment.

Cyanobacteria represent a promising resource for sustainable agriculture, as they have demonstrated the ability to restore soil fertility even after death and decay. However, several cyanobacteria can also release secondary metabolites, such as cyanotoxins, which may compromise the quality of agricultural products and pose a potential risk to human health. Depending on the concentration of exposure, few studies reported deleterious effects on plant species when irrigated with cylindrospermopsin (CYN) contaminated water, impairing plant growth and leading to food product contamination, while other studies show promoting effects on plant yield. To evaluate the potential of cyanobacterial biomass (cyanotoxin-containing or not) as a sustainable resource for soil amendment, biostimulants or fertilizers for lettuce cultivation, a study was carried out that consisted of the culture of lettuce plants under controlled conditions, in soil: (1) with no extra nutrient addition (control) and supplemented with 0.6 g of freeze-dried Raphidiopsis raciborskii biomass of (2) a non-CYN-producing strain, (3) a CYN-producing strain, and (4) the same CYN-producing strain pasteurized. Results showed no significant differences in photosystem II efficiency with the amendment addition. On the contrary, shoot fresh weight significantly increased in lettuce plants grown with the cyanobacterial biomass addition, especially in condition (3). In addition, there were significant differences in mineral concentrations in lettuce leaves after the cyanobacterial biomass addition, such as K, Na, Ca, P, Mg, Mn, Zn, Cu, Mo, and Co. CYN accumulation was detected under conditions (3) and (4), with concentrations observed in descending order from roots > soil > shoot. Nevertheless, the CYN concentration in edible tissues did not exceed the WHO-proposed tolerable daily intake of 0.03 µg/kg/day. These findings suggest that incorporating cyanobacterial biomass as a soil amendment, biostimulant or fertilizer for lettuce cultivation, even with trace amounts of CYN (1-40 µg/g), may enhance plant yield without leading to cyanotoxin accumulation in edible tissues above the WHO-recommended tolerable daily intake.