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The bell pepper is a vegetable with high antioxidant content, and its consumption is important because it can reduce the risk of certain diseases in humans. Plants can be affected by different types of stress, whether biotic or abiotic. Among the abiotic factors, there is saline stress that affects the metabolism and physiology of plants, which causes damage, decreasing productivity and quality of fruits. The objective of this work was to evaluate the application of selenium, silicon and copper nanoparticles and saline stress on the bioactive compounds of bell pepper fruits. The bell pepper plants were exposed to saline stress (25 mM NaCl and 50 mM) in the nutrient solution throughout the crop cycle. The nanoparticles were applied drenching solution of these to substrate (Se NPs 10 and 50 mg L−1, Si NPs 200 and 1000 mg L−1, Cu NPs 100 and 500 mg L−1). The results show that saline stress reduces chlorophylls, lycopene, and β-carotene in leaves; but increased the activity of some enzymes (e.g., glutathione peroxidase and phenylalanine ammonia lyase, and glutathione). In fruits, saline stress decreased flavonoids and glutathione. The nanoparticles increased chlorophylls, lycopene and glutathione peroxidase activity in the leaves; and ascorbate peroxidase, glutathione peroxidase, catalase and phenylalanine ammonia lyase activity, and also phenols, flavonoids, glutathione, β-carotene, yellow carotenoids in fruits. The application of nanoparticles to bell pepper plants under saline stress is efficient to increase the content of bioactive compounds in fruits.

The vigorous behaviour of a rootstock modifies the growth and yield of a plant variety or hybrid, altering the plant nutritional requirements. The purpose of this work was to study four ratios of NO3-/NH4+ (100/0, 92/8, 85/15 and 80/20%) over the growth, leaf anatomy and yield of grafted and ungrafted tomato plants. We used a fully randomised experimental block design with factorial arrangement of 2 × 4 (grafted and ungrafted plants and four ratios of NO3-/NH4+), on eight treatments in total with four replicates each, using Tukey's mean comparison test (P ≤ 0.05). The rootstock was 'Silex' by Fito Seeds, with the 'El Arrojado' graft (variety) by Gene Seeds. The graft produced an increase in growth, dry biomass production, stomatal density, trichome number, epidermal cell density, fruits per plant, average fruit weight, fruit size and total soluble solids, in comparison with the ungrafted tomato plants. In most of the assessed variables, the grafted tomato plants gave their best response at an 85/15% NO3-/NH4+ ratio; while the ungrafted plants performed better at a 92/8% NO3-/NH4+ ratio. The response of the grafted plants to the different NO3-/NH4+ ratios suggests that grafting induces tolerance to NH4+.

Water stress decreases the quality of fruit by generating reactive oxygen species. Grafting is a technique that can improve the efficiency of crop water usage. This work was performed in order to assess the effect of different water stresses on the commercial and nutraceutical quality of a melon fruit. Cantaloupe melon plants, grown under shade houses were grafted onto a creole pumpkin rootstock and grown with different water stresses (20, 30, and 40 kPa). The grafted melon plants under 30-kPa water stress (G30) showed greater fruit firmness and increased catalase activity. The G30 fruits showed an increase in GPX activity of up to 80% over the non-grafted plants. The GSH was higher in fruits subjected to the 40-kPa water tension. The superoxide dismutase showed a 15% greater inhibition in the fruits from the non-grafted plants. At higher water tensions, the DPPH antioxidant activity decreased, while the vitamin C content increased.

The use of nanoparticles (NPs) has generated an alternative pest control. The objective was to evaluate the insecticidal effect of zinc oxide nanoparticles (ZnO NPs), titanium dioxide nanoparticles (TiO2 NPs), and their combination on Bactericera cockerelli (Hemiptera: Triozidae) second-stage nymphs under laboratory and greenhouse conditions in tomato. The laboratory research was carried out with the leaf immersion bioassay method under a complete randomized design, and in the greenhouse by direct plant spraying under a randomized block design; in both designs, a control without NPs was added. Mortality was recorded every 24 h for 4 days. Both NPs in the laboratory and greenhouse showed toxicity to B. cockerelli nymphs. Results in the laboratory showed that NPs significantly caused increased mortality of 88, 99, and 100% 96 h after treatment of ZnO NPs, TiO2 NPs, and their combinations, at 1000, 100, and 250 ppm, respectively. Direct spray of plants in the greenhouse showed low mortality with 27, 32, and 23% after 96 h of ZnO NPs, TiO2 NPs, and their combinations, at 3000, 500, and 250 ppm, respectively. These results on B. cockerelli control seem promising. Nanoparticles as insecticides are a novel strategy, however, further investigation is required in field tests to obtain suitable efficacy for use in a pest management system.

The valorization of agro-industrial residues through fermentation processes represents a sustainable approach to producing high-value bioproducts, such as microbial organic acids and fermentation-derived anti-browning agents, including kojic acid and kojic acid-rich fermented extracts. In this study, melon waste (non-commercial-quality or damaged fruit) was evaluated as an alternative carbon source (whole fruit) for kojic acid (KA) production by Aspergillus oryzae (ATCC 10124) under submerged fermentation. The effects of process variables such as pH, temperature, and nitrogen and carbon availability on KA synthesis were analyzed, and biomass growth and product formation were described using logistic and Luedeking–Piret kinetic models. Under optimal conditions (pH 5.5, 36 °C, 2.5 g/L melon dry matter, 2.5 g/L yeast extract, 100 rpm), KA production reached 1.64 g/L at a final time of 120 h. Kinetic analysis showed moderate fungal growth (μmax = 0.058 h−1; Xmax = 0.81 g/L), with KA formation following a mixed growth-associated pattern as described by the Luedeking–Piret model (α = 1.26 g KA/g X; β = 0.024 h−1), indicating sustained production during the stationary phase. The KA-rich fermented extract was subsequently applied as an anti-browning treatment on spineless prickly pear (Opuntia ficus-indica) cladodes. Short immersion times (0.5–1.0 min) in a 2 g/L KA solution significantly preserved luminosity (L*) and limited total color change (ΔE ≤ 5) during 4 days of storage at 28 °C, compared with water-treated controls, which exhibited accelerated darkening (ΔE ≈ 9–15). Prolonged immersion times induced tissue damage and color deterioration, indicating an optimal exposure window. These results demonstrate the feasibility of valorizing melon waste to obtain a KA-rich extract and support its potential application as a natural anti-browning agent in fresh-cut vegetables within a circular agrifood framework.

Blueberry (Vaccinium corymbosum L.) continues to gain importance in the international market due to its effects on the prevention of human diseases. This leads to the need to optimize the production and quality of the fruit. The present research evaluated the effect of NO3- and NH4+, using the split roots technique, in the nutritional status, photosynthetic pigments and total sugars in blueberry leaves. A completely random experiment was established with six greenhouse treatments: three under homogeneous root conduction (HR) and three with split roots (SR). The concentration of N, P, K, Ca, Mg, S, Fe, Cu, Zn, Mn, B and Na, chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoids (Car) and total sugars were evaluated in the leaves. The exclusive supply of NH4+ led to the largest accumulation of N, P, Mg, S, Cu, Mn and B, compared to plants treated with NO3-. The Chla and total sugars were higher with NH4+ compared to NO3- nutrition. The supply of N separately (SR) had no positive effects on the evaluated variables, however, the SR with half of N, in the form of NH4+, compared to the non-SR with full application of N, has no differences in N-leaf concentration, which implies a higher use in the uptake or accumulation of this macro element in plant. V. corymbosum L. with split root and half of N in the form of NH4+, doubled the N use efficiency, as it matches in yield the complete supply treatment of N-NH4+ without root division.

The bell pepper (Capsicum annuum L.) is a food vegetable with a high nutritional intake, with rich content in vitamins, minerals and antioxidants. In this study, using nutrient film technique (NFT) system, the effect of the zinc oxide nanoparticles on the micromorphology, histology, physiology and production of the grafted pepper was evaluated. The treatments used were grafted and non-grafted plants, four concentrations (0, 10, 20, 30 mg L-1) of zinc oxide nanoparticles, and the experience was organized in a completely randomized design. An increase in grafted plants was observed in the weight, number and size of fruits in 18.1%, 21.8% and 9.6%, the concentration 30 mg L-1 of nanoparticles statistically affected the weight, number and size 46.9%, 47.7% and 18% compared to the control. The interaction with grafted plants and the treatment of 30 mg L-1 of zinc oxide nanoparticles increased fruit weight, number of fruits and size by 62.60%, 57.69% and 29.17% compared to plants without grafting and the control treatment. These results indicate that the use of grafts and zinc oxide nanoparticles could be used in bell pepper production to increase yield.

Selenium (Se) is an essential element of the human diet. Therefore, it is necessary to implement Se in selenium-deficient soils and in the nutrient solution of soilless system culture. Although it is not considered as an essential element for plants, Se provides benefits at the level of redox metabolism, increasing the resistance of plants to various stress factors. The increase of the availability of Se, with the use of biopolymer complexes, was sought in Lactuca sativa var. Great Lakes, grown in substrate pots treated with SeO2 (5 mg Se/plant), chitosan-polyacrylic acid complex + Se (Cs-PAA + Se) (5 mg Se/plant), and chitosan-polyacrylic acid complex (Cs-PAA). The redox metabolism was modified by increasing the enzymatic activity of catalase and glutathione peroxidase. The use of Cs-PAA + Se biopolymer complexes increased Se up to 24 mg/Kg dry weight (DW) in plant tissues.

Biostimulants are materials that when applied in small amounts are capable of promoting plant growth. Nanoparticles (NPs) and nanomaterials (NMs) can be considered as biostimulants since, in specific ranges of concentration, generally in small levels, they increase plant growth. Pristine NPs and NMs have a high density of surface charges capable of unspecific interactions with the surface charges of the cell walls and membranes of plant cells. In the same way, functionalized NPs and NMs, and the NPs and NMs with a corona formed after the exposition to natural fluids such as water, soil solution, or the interior of organisms, present a high density of surface charges that interact with specific charged groups in cell surfaces. The magnitude of the interaction will depend on the materials adhered to the corona, but high-density charges located in a small volume cause an intense interaction capable of disturbing the density of surface charges of cell walls and membranes. The electrostatic disturbance can have an impact on the electrical potentials of the outer and inner surfaces, as well as on the transmembrane electrical potential, modifying the activity of the integral proteins of the membranes. The extension of the cellular response can range from biostimulation to cell death and will depend on the concentration, size, and the characteristics of the corona.

Early blight is a disease that greatly affects Solanaceae, mainly damaging tomato plants, and causing significant economic losses. Although there are methods of biological control, these are very expensive and often their mode of action is slow. Due to this, there is a need to use new techniques that allow a more efficient control of pathogens. Nanotechnology is a new alternative to solve these problems, allowing the creation of new tools for the treatment of diseases in plants, as well as the control of pathogens. The aim of the present investigation was to evaluate the foliar application of selenium and copper in the form of nanoparticles in a tomato crop infested by Alternaria solani. The severity of Alternaria solani, agronomic variables of the tomato crop, and the changes in the enzymatic and non-enzymatic antioxidant compounds were evaluated. The joint application of Se and Cu nanoparticles decreases the severity of this pathogen in tomato plants. Moreover, high doses generated an induction of the activity of the enzymes superoxide dismutase, ascorbate peroxidase, glutathione peroxidase (GPX) and phenylalanine ammonia lyase in the leaves, and the enzyme GPX in the fruit. Regarding non-enzymatic compounds in the leaves, chlorophyll a, b, and totals were increased, whereas vitamin C, glutathione, phenols, and flavonoids were increased in fruits. The application of nanoparticles generated beneficial effects by increasing the enzymatic and non-enzymatic compounds and decreasing the severity of Alternaria solani in tomato plants.