Iron fertilizers are worthy to be studied due to alleviate the Fe deficiency. Different forms of iron oxide nanoparticles are selected to better understand possible particle applications as an Fe source for crop plants. In this study, we assessed the different effects of γ-Fe2O3 and Fe3O4 NPs on the physiology and fruit quality of muskmelon plants in a pot experiment for five weeks. Results showed that no increased iron content was found under NPs treatment in root, stem, leaf and fruit, except 400 mg/L Fe3O4 NPs had a higher iron content in muskmelon root. With the extension of NPs exposure, both γ-Fe2O3 and Fe3O4 NPs began to promote plant growth. In addition, γ-Fe2O3 and Fe3O4 NPs could increase chlorophyll content at a certain stage of exposure. Happily, 200 mg/L γ-Fe2O3 NPs and 100, 200 mg/L Fe3O4 NPs significantly increased fruit weight of muskmelon by 9.1%, 9.4% and 11.5%. It is noteworthy that both γ-Fe2O3 and Fe3O4 NPs caused positive effects on VC content, particularly 100 mg/L Fe3O4 NPs increased the VC content by 46.95%. To the best of our knowledge, little research has been done on the effect of nanoparticles on the whole physiological cycle and fruit quality of melon. The assessment of physiology and fruit quality of muskmelon plants in vitro upon γ-Fe2O3 and Fe3O4 NPs exposure could lay a foundation for NPs potential impact at every growth period of muskmelon plants.

The scarce availability of good quality water for irrigation in semi-arid regions leads to the reuse of waters, such as reject brine. Associated with this, the use of alternatives, such as hydroponic cultivation in substrates suitable for the development of profitable crops, such as watermelon, a species considered moderately sensitive to salinity, will allow new opportunities for communities assisted by desalination plants. An experiment was conducted in a plastic greenhouse to evaluate the growth, physiological responses, yield, and fruit quality of ‘Sugar Baby’ mini-watermelon cultivated in a hydroponic system with reject brine from desalination plants and different substrates. The experimental design was randomized blocks, with treatments arranged in a 5 × 4 factorial scheme, corresponding to five mixtures of reject brine (9.50 dS m⁻¹) and tap water (0.54 dS m⁻¹) applied to mini-watermelon plants, in an open hydroponic system, with four types of substrate and four replicates, with two plants per plot. Mini-watermelon plants grown in coconut fiber substrate showed the best growth and production. On the other hand, washed sand was the substrate that most hampered the development of plants in all mixtures. The use of reject brine to prepare the nutrient solution reduced the growth and production of mini-watermelon, mainly in mixtures with salinity above 4.00 dS m⁻¹. The changes in gas exchange caused by salt stress in mini-watermelon were of stomatal nature. Mini-watermelon has high energy stability under conditions of salt stress.

The atmosphere over Brazilian cities is influenced by a variety of emissions sources. In this study, aerosol collection and back-trajectory analysis were used to determine the influence of local and remote sources. Aerosols were collected at three locations within the state of São Paulo: one megacity and two cities in which sugar cane burning in the surroundings is observed. We quantified the major water-soluble inorganic ions and trace metals. As expected, vehicle emissions influenced the atmosphere of the megacity heavily, and sugar cane burning influenced that of the other locations. During the period of this experiment the back-trajectory analysis revealed that air masses are transported into the state from the northeast of Brazil, where biomass burning occurs. Multivariate statistical analysis revealed that the two principal components account for 48.5% of the total data variance. We conclude that local sources have a strong impact on the concentrations of particulate matter and pollutants. Remote sources also contribute to the concentrations of aerosol pollutants.

The objective of the present study was to assess the response of tomato cultivars with different fruit colors to exposure to increasing Cd levels in the substrate by measuring the impacts of Cd on the oxidative stress indicators and physicochemical features of fruits, as well as plant development and yield components. A completely randomized experiment in a 3 × 3 factorial design [tomato cultivar (which produces purple, red, or white fruits) vs Cd level in the substrate (0, 3.6, or 12 mg kg⁻¹)] was performed. The cultivation of plants in substrate containing 3.6 mg kg⁻¹ Cd did not affect yield, but fruits exhibited nonpermissive Cd concentrations in both peel and mesocarp across all cultivars. By contrast, yield was decreased in plants with red and white fruits after their cultivation in substrate containing 12 mg kg⁻¹ Cd, while the productivity of plants with purple fruits was maintained under such conditions. The hydrogen peroxide content in the fruit mesocarp depended only on cultivar. However, an increased lipid peroxidation level was detected in the mesocarp of purple fruits at the highest Cd concentration. No parameters of fruit quality [i.e., diameter, length, °Brix, pH, titratable acidity, color (L*, a*, and b*), and concentrations of lycopene and β-carotene in mesocarp] were affected by long-term exposure to Cd at 12 mg kg⁻¹. In conclusion, the results of this study suggested that the potential Cd side effects on diverse tomato quality features can be buffered at the fruit level because these features were maintained at the usual values despite high Cd concentrations in tomato peel and pulp. Moreover, these buffering mechanisms are independent of lycopene and β-carotene concentrations in fruit peel, since the three tomato cultivars that were evaluated in the present study (white fruits, possessing no or negligible concentrations of these carotenoids, and red and purple tomato, possessing high lycopene and β-carotene concentrations) were able to sustain several fruit quality parameters after long-term exposure to high Cd concentrations in the substrate.

Iron deficiency has been becoming a worldwide problem in crop cultivation. New approaches are desired to alleviate the iron-deficit chlorosis. Iron-containing nanomaterials could be effective to supply the iron to plants and promote plant growth. In this study, soil cultured watermelon plants were treated with 100, 200, and 400 ppm α- and γ-Fe₂O₃ nanoparticles (NPs), respectively. Growth and physiology parameters were investigated in a period of time. The study also evaluated the nutritional quality of watermelon fruit. Results showed that no elevation of plant growth or chlorophyll content was observed. All α- and γ-Fe₂O₃ NPs treatments had no positive influence on nutritional components including central and edge sugar content, and total amino acid content. An interesting result was that the vitamin C (VC) content of all NP treatments was significantly improved compared with the control group (without iron). In addition, we found that iron distribution of α- and γ-Fe₂O₃ NPs treatments was closely related to the concentrations of NPs. Both α- and γ-Fe₂O₃ NPs could accumulate in root, stem, and leaf of watermelon plants, but only 400 ppm γ-Fe₂O₃ NPs treatment was found to exist in watermelon fruit. Although no promotion of α- and γ-Fe₂O₃ NPs on the growth of watermelon plants was occurred, our results showed that both α- and γ-Fe₂O₃ NPs could enter plant roots and translocate upwards to other tissues. Our finds will provide data for the future applications of iron-containing nanomaterials in agricultural production. Graphical Abstract

Silicon has been regarded as a promising technology to improve nutrient supply to plants. This study aimed to evaluate the influence of different nitrogen doses on mineral nutrition and fruit quality of zucchini cv. Caserta SH-202 with and without foliar silicon application. An experiment was conducted under field conditions to evaluate the effects of five levels of nitrogen (30, 60, 90, 120, and 150 kg ha⁻¹ N) and silicon application (without and with foliar application). The N levels were split into smaller aliquots and applied at three different times, while Si was equally split into two applications, with the first at 14 days after planting (DAS) and the second at 28 (DAS) via foliar application. Using the leaves during the flowering period, individual leaf samples were collected at 28 (DAS) from the intermediate branches of plants in each plot to evaluate the contents of N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, Zn, and Na. The following quality parameters were obtained at 55 (DAS): potential of hydrogen (pH), soluble solids (Brix), titratable acidity, and ascorbic acid (vitamin C). Nitrogen fertilization promoted adequate nutrition for zucchini of N, P, K, Ca, Mg, B, Cu, Mn and Zn, related to the application of silicon, which is also suitable for fruit quality in the pH, Brix, titratable acidity, and vitamin C. Considering the adequate nutritional value of zucchini, the level of nitrogen fertilization recommended with silicon ranges from 20 to 40 g plant⁻¹.

This study was conducted to compare organic fertilization (OF) with conventional fertilization (CF) in tomato crop with respect to the following specific objectives: (i) to evaluate the contents of applied and available nutrients in the soil; (ii) to evaluate the production, commercial, and nutraceutical quality of tomato fruit; and (iii) to study the relationship of the contents of available nutrients in the soil with the variables affecting the production and quality of tomato fruits. Four treatments were established: OF (1) 6 t ha⁻¹ poultry manure + poultry manure tea and (2) 9 t ha⁻¹ poultry manure + poultry manure tea; CF (3) 180–90-00 and (4) 270–135-00 (N, P₂O₅, and K₂O, respectively). The results show that OF contributed more available nutrients to the soil than CF. OF promoted more fruit yield than CF, as well as more total phenol and antioxidant content in fruits. The higher the doses applied, within each form of fertilization, the higher the agronomic yield, but fruit quality and antioxidant capacity were not affected. The soil variables that were most strongly related to total phenols and antioxidants in tomato fruit were soil available Mn, pH, and electrical conductivity. Both forms of fertilization, organic and conventional fertilization, are different in terms of applied and available nutrients in the soil that nourish the plants and have a consequent effect on the antioxidant capacity of the fruit.

The use of soil conditioners as bovine biofertilizer associated with mineral fertilization affect the physical and physicochemical quality of passion fruit. For fruit growth, post-harvest quality is crucial for production chain development, as it is the characteristic most used by the fresh consumption market for this fruit. In this sense, an experiment was carried out to investigate the effects of doses of bovine biofertilizer in the soil with and without nitrogen fertilization in the cultivation of yellow passion fruit. A randomized block design was adopted, with three replications in a 5×2 factorial scheme, referring to five doses of liquid bovine biofertilizer (B) diluted in water (A): 0% − control (0B + 4A); 25% (1B + 3A); 50% (2B + 2A); 75% (3B + 1A); and 100% (4B + 0A) with and without nitrogen fertilization applied to the soil. Urea was the nitrogen source used in this study. A total of 10 g plant⁻¹ of N was applied monthly at 30 and 60 days after transplanting, and after that age, 20 g plant⁻¹ was applied until the end of harvest. During the final phase of production and ripening, twelve fruits were harvested from each treatment in physiological maturation for physical and physicochemical characterization. The following analyses were performed: longitudinal diameter, transversal diameter, number of seeds per fruit, peel firmness, pulp yield, fruit peel percentage, pulp pH, soluble solids content; titratable acidity and soluble solids content/titratable acidity ratio. Data underwent analysis of variance by the F test means for nitrogen were compared by Tukey’s test and means for bovine biofertilizer, by regression. Nitrogen enhances the positive effect of bovine biofertilizer on the postharvest quality of yellow passion fruit. The association of biofertilizer and nitrogen improves fruit quality in comparison to plants without these inputs, except for pulp yield and fruit peel percentage, which suffered isolated effects from the factors. High doses of biofertilizer, above 75 and 100%, reduce soluble solids content and increase titratable acidity. The bovine biofertilizer has promising effects, but it does not replace nitrogen fertilization on the postharvest quality of yellow passion fruit.

Microplastic pollution in farmlands has become a source of major concern, but few previous studies have focused on the effect of microplastics on higher plants. In this study, the distribution of polystyrene nanoplastics (PSNPs) of four different particle sizes (100, 300, 500, and 700 nm) was investigated in cucumber plants, and their influence on physiological indexes of the root system and fruit quality was determined. The results showed that PSNPs initially accumulated in the root system before being transported to the aboveground parts of the plant. Finally, they were distributed in the leaves, flowers, and fruits, through the stems. The 300-nm plastic microspheres significantly increased root activity and malondialdehyde (MDA) and proline content of the roots. The results demonstrated that the environmental pressures caused by PSNPs of different particle sizes were different. The amount of soluble protein in cucumber fruits was significantly increased, and the levels of Mg, Ca, and Fe were significantly decreased by PSNPs of different particle sizes. Our findings provide a scientific basis for risk assessment of PSNP exposure in the soil–plant systems.

Given a critical water scarcity in arid and semi-arid Tunisian areas and aiming to reduce irrigation water request, it is crucial to identify and apply the best water-saving practices in these irrigated areas. Tomato is a high-water-requiring vegetable crop, thus increasing the pressure on water resources and environment. Its sustainable cultivation in such alarming conditions requires an adaptation of on-farm irrigation water-saving strategies preserving also the crop yield and leading to a fruit quality improvement. This study aimed to explore the effects of the regulated deficit irrigation (RDI) as an irrigation water-saving strategy, on yield, fruit quality, and physiological behavior of greenhouse grown potted tomato crop (Solanum lycopersicum L.) during three identified growth stages. The managed water regimes were (i) full irrigation (FI) ensuring 100% of the estimated water crop requirements, (ii) RDI1-25 and RDI1-50 ensuring respectively 75% and 50% of FI water supplies during the vegetative crop stage (stage I), (iii) RDI2–25 and RDI2–50 ensuring respectively 75% and 50% of FI water supplies from first truss blossom until first harvest (stage II), and (iv) RDI3-25 and RDI3-50 ensuring respectively 75% and 50% of FI supplies during the rest of the harvest period (stage III). The results showed that the substrate moisture vary significantly with the water deficit regime applied under different growth stages, thus providing different levels of substrate water content. Under RDI2, the tomato yield was the highest when compared with FI, RDI1, and RDI3 regimes. Indeed, saving the water by 20% under RDI2-50 reduced only 3% of tomato yield. Deficit irrigation under ripening fruit and flowering stages, mainly with 50% of water supplies shortage, resulted in higher fruit skin color, firmness, and refractometry index (°Brix) when compared to FI and RDI1. Physiological traits measurements indicated that FI exhibited the highest leaf stomatal conductance (gs) and chlorophyll index (CI) values while RDI3 exhibited the lowest gs and CI values among all the RDI treatments. Results are valuable in considering gs and CI as an efficient indicators of tomato plant water status. The results are also an important contribution to identify the second tomato growth stage as the best period that tomato plant tolerate water shortage without significant yield decrease, as well a rather fruit quality improvement. These results help to reach the challenge “more crop per drop” and can contribute to water scarcity remediation.