Water deficit in the semi-arid region of Brazil is a critical limiting factor for tomato (Solanum lycopersicum Mill.), plant development and productivity. We evaluated whether foliar zinc (ZnO NPs) and iron (Fe₂O₃NPs) nano-oxides and their conventional salts (ZnSO₄·7H₂O and FeSO₄·7H₂O) mitigate water deficit effects on tomato (hybrid HM 2798). A split-plot field experiment was conducted with two irrigation levels (50% and 100% ETc) and five foliar treatments: control (no application), FeSO₄·7H₂O (T1), Fe₂O₃NPs (T2), ZnONPs (T3), ZnSO₄·7H₂O (T4), with four replications, totaling 40 experimental plots (2 irrigation levels × 5 foliar treatments × 4 replicates). The water deficit significantly reduced the leaf area index, photosynthetic rate, membrane stability, calcium and boron contents in fruits, and total and marketable yield. Foliar application of iron and zinc nano-oxides and their conventional sources had a limited effect on tomato plant growth but increased the photosynthetic rate under both irrigation levels. Under full irrigation, ZnSO₄·7H₂O increased total fruit production by 61% and fruit Zn content by 18.1%. In turn, Fe₂O₃ NPs (T2) led increases in fruit iron content by 117.3% under water deficit and 135.2% under full irrigation. Foliar application of Fe as Fe₂O₃ NPs is promising to promote the biofortification of tomato fruits with this micronutrient, especially in regions with deficiency problems of this micronutrient.

Guava is one of the most economically important fruit crops grown in the Northeast region of Brazil. This region is characterized by a high concentration of salts in the water sources used for irrigation, necessitating the development of strategies to minimize the harmful effects of salt stress on production systems. The objective of this study was to analyze the effect of priming guava seeds with H2O2 on seedling production under salt stress. The experiment was conducted in a greenhouse at the Center for Agri-food Science and Technology at the Federal University of Campina Grande, located in Pombal, PB, Brazil. A randomized complete block experimental design was employed, involving a 5 × 3 factorial arrangement represented by five levels of electrical conductivity of irrigation water (ECw: 0.3, 1.1, 1.9, 2.7, and 3.5 dS m-1) and three concentrations of hydrogen peroxide (H2O2: 0, 25, and 50 µM). Four replications were used, with five plants per plot. Salinity in the water starting from 0.3 dS m-1 reduced growth, relative water content, photosynthetic pigments, dry biomass, and Dickson’s quality index, and increased the water saturation deficit in ‘Paluma’ guava seedlings 110 days after sowing. Hydrogen peroxide at a concentration of 25 µM increased the emergence speed index of seedlings, although its application at a concentration of up to 50 µM did not alleviate the adverse impacts of salt stress on ‘Paluma’ guava seedlings under an electrical conductivity of irrigation water of 3.5 dS m-1.

Water deficit is a critical limiting factor for tomato plant development and productivity, reducing photosynthesis, membrane stability, fruit nutrient content, and yield. This study evaluated the efficacy of zinc oxide nanoparticles (ZnO NPs) and iron oxide nanoparticles (Fe₂O₃NPs), compared to their conventional forms (ZnSO₄·7H₂O and FeSO₄·7H₂O), in mit-igating water stress (50% ETc) under field conditions. Tomato (Solanum lycopersicum Mill.), hybrid HM 2798 was utilized as the experimental material. A split-plot field experiment was conducted with two irrigation levels (50% and 100% ETc) and five foliar treatments: Control (no application), FeSO₄·7H₂O (T1), Fe₂O₃NPs (T2), ZnONPs (T3), ZnSO₄·7H₂O (T4), with four replications. The water deficit significantly reduced the leaf area index, photo-synthetic rate, membrane stability, calcium and boron contents in fruits, and total and marketable yield. Foliar application of iron and zinc had a limited effect on tomato plant growth but increased the photosynthetic rate under both irrigation levels. Notable results included a 61% increase in total yield under full irrigation with ZnSO₄·7H₂O (T4), and a 117.3% increase in fruit iron content under water deficit with Fe₂O₃ NPs (T2). It is con-cluded that ZnSO₄·7H₂O was the most effective treatment in mitigating water stress, sug-gesting conventional zinc supplementation as a viable strategy to sustain tomato produc-tion under water restriction.

Purple basil (Ocimum basilicum L.) is a medicinal plant widely recognized for its richness in bioactive compounds; however, its production in semi-arid regions is often constrained by soil and/or irrigation water salinity. Micronutrient fertilization may contribute to plant stress alleviation under salinity, since elements such as Mn, Mo, and Zn are involved in essential processes related to photosynthetic metabolism and physiological adjustment. This study aimed to evaluate the short-term effects of Mn, Mo, Zn, and their combinations on growth, gas exchange, and relative chlorophyll indices of purple basil plants subjected to severe NaCl stress under greenhouse conditions. The experiment was conducted under greenhouse conditions for 30 days in a randomized block design with nine treatments and four replicates: a non-saline control without micronutrients, a saline control without micronutrients, and plants exposed to 100 mM NaCl with substrate application of Mn, Mo, Zn, MoMn, ZnMo, ZnMn, or ZnMoMn. Micronutrient sources were applied to the substrate at 3.5 g kg⁻¹ according to each treatment. Fertilization with Mn, Mo, Zn, and their combinations enhanced plant stress alleviation under salinity compared with the saline control without micronutrients, with positive responses in growth and physiological performance, including increases in chlorophyll indices. The double combinations MoMn, ZnMo, and ZnMn attenuated the effects of NaCl, especially by increasing leaf area. Mn stood out for increasing net photosynthesis and water-use efficiency, whereas Mo and ZnMo were associated with higher relative chlorophyll indices. Although the triple combination ZnMoMn improved some traits compared with the saline control, its lower efficacy relative to selected single or double applications may indicate that the simultaneous supply of the three elements reduced specific synergistic effects, possibly due to nutritional imbalance or antagonistic interactions among micronutrients under severe salinity. Overall, micronutrient fertilization, particularly through specific double combinations, may contribute to short-term mitigation of NaCl-induced stress responses under controlled greenhouse conditions.