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Reduction of nitrogen application in crop production is desirable for ecological and health-related reasons. Interestingly, nitrogen deficiency can lead to enhanced concentrations of polyphenols in plants. The reason for this is still under discussion. The plants' response to low nitrogen concentration can interact with other factors, for example radiation intensity. We cultivated red and green leaf lettuce hydroponically in a Mediterranean greenhouse, supplying three different levels of nitrogen (12 mM, 3 mM, 0.75 mM), either in full or reduced (-50%) radiation intensity. In both red and green lettuce, we found clear effects of the nitrogen treatments on growth characteristics, phenolic and photosynthetic compounds, nitrogen, nitrate and carbon concentration of the plants. Interestingly, the concentrations of all main flavonoid glycosides, caffeic acid derivatives, and sucrose increased with decreasing nitrogen concentration, whereas those of chlorophylls, [beta]-carotene, neoxanthin, lactucaxanthin, all trans- and cis-violaxanthin decreased. The constitutive concentrations of polyphenols were lower in the green cultivar, but their relative increase was more pronounced than in the red cultivar. The constitutive concentrations of chlorophylls, [beta]-carotene, neoxanthin, all trans- and cis-violaxanthin were similar in red and green lettuce and with decreasing nitrogen concentration they declined to a similar extent in both cultivars. We only detected little influence of the radiation treatments, e.g. on anthocyanin concentration, and hardly any interaction between radiation and nitrogen concentration. Our results imply a greater physiological plasticity of green compared to the red lettuce regarding its phenolic compounds. They support the photoprotection theory regarding anthocyanins as well as the theory that the deamination activity of phenylalanine ammonia-lyase drives phenylpropanoid synthesis.

Movement proteins (MPs) modulate the size exclusion limit of plasmodesmata—membrane‐lined channels connecting plant cells—thereby allowing cell‐to‐cell movement and systemic spread of plant viruses. The largest and arguably best‐studied group of MPs is the 30K superfamily. Its family members share little sequence similarity, with only a handful of residues being well conserved. Yet, all family members appear to adopt the same jelly‐roll protein fold structure. Lettuce big‐vein associated virus (LBVaV), a member of the Rhabdoviridae family, is closely associated with lettuce big‐vein disease (LBVD). It appears to facilitate the long‐distance movement of Mirafiori lettuce big‐vein virus (MiLBVV) in plants through an unknown mechanism. Notably, enhanced MiLBVV spread correlates with severe LBVD symptoms. Despite LBVaV having been known for decades, its proteins have not been studied in detail thus far. By using a combination of Alphafold2 structure modelling and FoldSeek structure‐based homology searches, we managed to annotate all LBVaV open reading frames (ORFs), with ORF3 clustering with the 30K superfamily. While ORF3 is the most conserved protein sequence among the LBVaV‐encoded ORFs, it shares only 5%–11% protein sequence identity with related MPs in the same genus. Microscopy studies confirmed that ORF3 locates at plasmodesmata, and in planta expression of ORF3 allowed cell‐to‐cell movement of two movement‐impaired plant viruses. Thus, the Alphafold2‐FoldSeek strategy allowed successful annotation of a plant viral genome even when viral proteins show little sequence similarity. AlphaFold2 + FoldSeek structure guided search predicts the movement protein of lettuce big‐vein associated virus despite low sequence similarity.

Harvesting is an important procedure for hydroponic lettuces in plant factories. At present, hydroponic lettuces are mainly harvested manually, and the key difficulty in mechanical harvesting is reducing the occurrence of leaf injury. Measuring the size of hydroponic lettuces using the image processing method and intelligently adjusting the operating parameters of the harvesting device are the foundation of high-quality harvesting for lettuces. The overlapped leaves of adjacent hydroponic lettuces cause difficulties in measuring lettuce size, especially the leaves expansion size. Therefore, we proposed an image processing method for measuring lettuce height and leaves expansion size according to the upper contour feature of lettuces and an image included three lettuces. Firstly, the upper contours of the lettuces were extracted and segmented via image preprocessing. Secondly, lettuce height was measured according to the maximum ordinate of the contour. Lastly, the lettuce’s upper contour was fitted to a function to measure the leaves expansion size. The measurement results showed that the maximal relative error of the lettuce height measurements was 5.58%, and the average was 2.14%. The effect of the quadratic function in fitting the upper contour was the best compared with the cubic function and sine function. The maximal relative error of the leaves expansion size measurements was 8.59%, and the average was 4.03%. According to the results of the lettuce height and leaves expansion size measurements, the grabbing parameters of each lettuce were intelligently adjusted to verify the harvesting effect. The harvesting success rates of lettuces was above 90%, and the injured leaves areas of the left, middle, and right lettuces in each image were 192.6 mm2, 228.1 mm2, and 205.6 mm2, respectively. This paper provides a reference for the design and improvement of intelligent harvesters for hydroponic lettuces.

Plant endophytic bacteria live inside host plants, can be isolated from surface-sterilized plant tissues, and are non-pathogenic. These bacteria can assist host plants in obtaining more nutrients and can improve plant growth via multiple mechanisms. Certain Gram-negative Burkholderia species, including rhizobacteria, bioremediators, and biocontrol strains, have been recognized for their plant-growth-promoting abilities, while other isolates have been identified as opportunistic plant or human pathogens. In this study, we observed the auxin production, siderophore synthesis, and phosphate solubilization abilities of B. seminalis strain 869T2. Our results demonstrated that strain 869T2 promoted growth in Arabidopsis, ching chiang pak choi, pak choi, loose-leaf lettuce, romaine lettuce, red leaf lettuce, and Chinese amaranth. Leafy vegetables inoculated with strain 869T2 were larger, heavier, and had more and larger leaves and longer and heavier roots than mock-inoculated plants. Furthermore, inoculations of strain 869T2 into hot pepper caused increased flower and fruit production, and a higher percentage of fruits turned red. Inoculation of strain 869T2 into okra plants resulted in earlier flowering and increased fruit weight. In conclusion, the plant endophytic bacterium Burkholderia seminalis 869T2 exerted positive effects on growth and production in several plant species.

The affordability of packaging materials and proper storage facilities to preserve the quality of lettuce (Lactuca sativa L.) has become a problematic issue for small-scale farmers in Malaysia, who have limited resources and rely on their crops for income. This study compares the post-harvest quality preservation of lettuce using plastic bags and newspapers as cost-effective packaging materials under storage durations of 0, 3, 6, 12, and 15 days. The lettuce quality parameters measured were chlorophyll, sucrose, weight loss, and overall visual quality (OVQ). The results showed newspapers had the highest mean weight loss (7.91 g), while plastic had the lowest one (5.81 g). However, chlorophyll content did not significantly differ between the two packaging types. Lettuce packaged in plastic bags had a significantly lower total soluble solids (TSS) content mean value (2.89%) compared to newspaper (3.89%). In addition, the plastic bag materials gave a better OVQ than that of the newspaper. Generally, the use of plastic bags as a packaging option for small-scale lettuce farmers in Malaysia is affordable and readily available.

The effects of different spectral compositions of light-emitting diode (LED) sources and fertilizer containing biologically active silicon (Si) in the nutrient solution on morphological and physiological plant response were studied. Qualitative indicators and the productivity of plants of a red-leaved and a green-leaved lettuce were estimated. Lettuce was grown applying low-volume hydroponics in closed artificial agroecosystems. The positive effect of Si fertilizer used as a microadditive in the nutrient solution on the freshly harvested biomass was established on the thirtieth day of vegetation under LEDs. Increase in productivity of the red-leaved lettuce for freshly harvested biomass was 26.6%, while for the green-leaved lettuce no loss of dry matter was observed. However, being grown under sodium lamps, a negative impact of Si fertilizer on productivity of both types of plants was observed: the amount of harvested biomass decreased by 22.6% and 30.3% for the green- and red-leaved lettuces, respectively. The effect of using Si fertilizer dramatically changed during the total growing period: up to the fifteenth day of cultivation, a sharp inhibition of the growth of both types of lettuce was observed; then, by the thirtieth day of LED lighting, Si fertilizer showed a stress-protective effect and had a positive influence on the plants. However, by the period of ripening there was no effect of using the fertilizer. Therefore, we can conclude that the use of Si fertilizers is preferable only when LED irradiation is applied throughout the active plant growth period.

The agrotechnical methods of biofortification of plants, i.e., enriching them in iodine (I) and selenium (Se) could be effective methods to enrich food products in these elements. The advantage of agrotechnical methods of biofortification is the incorporation of elements in organic compounds in plants; therefore, they have better health-promoting properties than pure technical salts. Two-year studies were conducted in a greenhouse with hydroponic cultivation of three botanical varieties of lettuce in an NFT (nutrient film technique) system: two cultivars butterhead lettuces (abb. BUTL) 'Cud Voorburgu' and 'Zimująca,' two cultivars iceberg lettuces (abb. ICEL) 'Maugli' and 'Królowa lata' (all this four cultivars are classified as L. var. ) as well two cultivars L. var. L. cultivars (abb. REDL) 'Lollo rossa' and 'Redin' having little red leaves. The study included the application of I (as KIO ), Se (as Na SeO ), and SA into the nutrient solution. The tested treatments were as follows: (1) control, (2) I+Se, (3) I+Se+0.1 mg SA dm , (4) I+Se+1.0 mg SA dm , and (5) I+Se+10.0 mg SA dm . KIO was used at a dose of 5 mg I dm , while Na SeO was 0.5 mg Se dm . Regardless of the kind of the applied compound, the highest biomass of heads was produced by the REDL 'Redin' variety. Furthermore, this variety, as the only one in six varieties tested, reacted with the decrease in yield to the application of I+Se and I+Se+three concentrations of SA. In the heads of all cultivars, the level of I accumulation was 10-30 times higher than of Se. The level of I accumulation formed the following order: REDL 'Lollo rossa' > REDL 'Redin' = BUTL 'Cud Voorburgu' > BUTL 'Zimująca' > ICEL 'Maugli' > ICEL 'Królowa lata'. The order of Se content in leaves was as follows: REDL 'Redin' = BUTL 'Cud Voorburgu' > REDL 'Lollo rossa' > ICEL 'Maugli' > BUTL 'Zimująca' > ICEL 'Królowa lata'. The obtained results indicate that the introduction of SA to the nutrient solutions in hydroponic systems may allow an improve the effectiveness of - biofortification.

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

Interest in aquaponics (AP) is increasing due to its ability to minimize sewage and maximize feed efficiency in fish farming. However, owing to limitations of intensive cultures and a lack of nutrients such as NO[sub.3] for growing crops, AP requires the use of artificial nutrients. Therefore, novel approaches are required to develop AP-intensive culturing methods. An AP system based on biofloc technology (BFT) called FLOCponics (FP) has been recommended. Here, the productivity of the weather loach (Misgurnus anguillicaudatus ) in the FP system, BFT system, and flow-through systems (FTSs), as well as these systems’ effect on Caipira lettuce (Lactuca sativa ) growth, was analyzed. To compare crop productivity, a hydroponic (HP) bed was installed. The growth rate of M. anguillicaudatus showed significant differences, at 51.1 ± 3.69% in the FP system, followed by 24.0 ± 4.16% in the BFT system and −14.3 ± 1.4% in the FTS. Its survival rates were better in the FP system (91.1 ± 2.64%) than in the BFT system (82.1 ± 10.98%) or the FTS (66.8 ± 2.75%) (p < 0.05). Total ammonia nitrogen and NO[sub.2] [sup.−] -N concentrations were stabilized in every plot during the experimental period. However, the NO[sub.3] [sup.−] -N concentration continuously increased in the BFT system but decreased in the FP system and was maintained. The shoot weight of the Caipira lettuce was 163.6 ± 8.65 g in the FP system and 149.6 ± 9.05 g in the HP system. In conclusion, FP system can provide a large amount of nutrients and improve the growth performance of both fish and crops in the FP system.

The ZIP protein (ZRT, the IRT-like protein) is an important metal transporter that transports Zn, Fe, and other divalent metal ions in plants. In this study, we identified 20 ZIP genes in lettuce (Lactuca sativa L.). We used bioinformatics methods and renamed them according to their E value in hmmsearch. We also analyzed their gene structure, chromosomal location, constructed a phylogenetic tree, conserved motifs, performed synonymous analysis and responses to abiotic stresses. The results show that these LsZIP genes have 3-11 exons and were distributed unequally on 8 of the 9 chromosomes in lettuce. Based on phylogenetic analyses, the LsZIP gene family can be divided into three subfamilies, and the LsZIP genes within the same subfamily shared similar gene structure. The LsZIP genes contain 12 Motifs, of which Motif1 to Motif8 are widely distributed in group â . Furthermore, the LsZIP gene contains numerous hormones and anti-stress response elements. Real-time quantitative PCR demonstrated that most LsZIP genes is up-regulated under the elemental stress in this experiment, indicating that they are positively regulated. But different elemental stressors can induce the expression of LsZIP gene to varying degrees. The LsZIP genes also change in response to different elemental stresses. The present study serves as a basic foundation for future functional studies on the lettuce ZIP family.