Green peppers (Capsicum annuum L.) are a fruit vegetable with great culinary versatility and present important nutritional properties for human health. Water deficit negatively affects the nutritional quality of green peppers’ fruits. This study aimed to investigate the influence of zinc oxide nanoparticles (ZnONPs), associated with plant growth-promoting bacteria (PGPB), on the post-harvest nutritional quality of green peppers subjected to water deficit. In an open-field experiment, two irrigation levels (50 and 100% of crop evapotranspiration (Etc)), four treatments composed of a combination of ZnONPs, zinc sulfate (ZnSO₄), and PGPB (T1 = ZnSO₄ via leaves, T2 = ZnONPs via leaves, T3 = ZnONPs via leaves + PGPB via soil, T4 = ZnSO₄ via soil + PGPB via soil), and a control treatment (Control) were tested. Water deficit or water deficit mitigation treatments did not interfere with the physical–chemical parameters (except vitamin C content) and physical color parameters (except the lightness) of green peppers. On average, the water deficit reduced the levels of Ca (−13.2%), Mg (−8.5%), P (−8.5%), K (−8.6%), Mn (−10.5%), Fe (−12.2%), B (−12.0%), and Zn (−11.5%) in the fruits. Under the water deficit condition, ZnONPs or ZnSO₄ via foliar, associated or not with PGPB, increased the levels of Ca (+57% in the T2 and +69.0% in the T2), P, Mg, and Fe in the fruits. At 50% Etc, the foliar application of ZnONPs in association with PGPB increases vitamin C and mineral nutrients’ contents and nutritional quality index (+12.0%) of green peppers. Applying Zn via foliar as ZnONPs or ZnSO₄ mitigated the negative effects of water deficit on the quality of pepper fruits that were enhanced by the Bacillus subtilis and B. amyloliquefaciens inoculation. The ZnONPs source was more efficient than the ZnSO₄ source. The water deficit alleviating effect of both zinc sources was enhanced by the PGPB.

Eggplant (Solanum melongena) is widely cultivated. It shows moderate tolerance to water deficit, but suffers yield losses in the arid and semi-arid regions where it is grown. The aim of this study was to investigate the influence of zinc oxide nanoparticles (NPZnO), in association with plant growth-promoting bacteria (PGPB), on the post-harvest quality of eggplant subjected to water deficit. Two irrigation percentages relative to potential evapotranspiration-ETo (50 and 100% ETo) and five combinations involving NPZnO or PGPB were studied. Number of commercial fruits per plant and weight of commercial fruits per plant, diameter, length, skin color, firmness, titratable acidity, soluble solids, SS/TA, vitamin C and total soluble sugars were evaluated. There was strong positive correlation between weight of commercial fruits per plant, SS/TA, total soluble sugars, titratable acidity, lightness and vitamin C in the treatments containing ZnSO₄, NPZnO and PGPB. Water deficit and nanoparticles containing zinc, associated or not with bacteria that promote plant growth, did not influence the weight and average size of the fruits and the post-harvest quality of the eggplant crop. Water deficit reduced the chromaticity and lightness of the skin color and the vitamin C content of eggplant.

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.

The limited availability of low-salinity water in the northeastern semi-arid region of Brazil is one of the main constraints to the expansion of irrigated agriculture. In this context, the objective of this study was to evaluate the effects of irrigation with saline water on the salinity tolerance of guava during the rootstock formation phase. The experimental design was a randomized complete block in a 2 x 5 factorial scheme, consisting of two guava genotypes (Crioula and cv. Paluma) and five levels of irrigation water electrical conductivity (ECw: 0.3, 1.2, 2.1, 3.0, and 3.9 dS m-1), with six replicates. Stem diameter, plant height, fresh biomass of leaves, stems, and roots, and the accumulation of dry biomass in leaves, stems, roots, and total biomass were measured, along with Dickson quality index, transpiration rate, stomatal conductance, CO2 assimilation rate, and the absolute and relative growth rates in plant height. Irrigation using water with electrical conductivity above 0.3 dS m-1 inhibited stem diameter growth, root dry biomass, leaf transpiration, relative growth rate in height, and Dickson quality index in guava seedlings. Among the genotypes, Crioula showed greater growth, photosynthetic activity, and Dickson quality index under saline water irrigation, indicating its potential for use as a rootstock under semi-arid conditions.

The search for better quality inputs with lower environmental impact has been highlighted in agricultural technology research. Microalgae can improve soil fertility and seedling development. This study aimed to evaluate the influence of suspensions as a biostimulant based on the microalgae Chlorella sp. applied via root on the production of ‘Cantaloupe’ melon seedlings. The experimental design used was completely randomized, with ten replications, in a scheme of split plots in time. The plots consisted of three concentrations (0.0, 0.8, and 1.6%) and the subplots consisted of five evaluation periods (15, 18, 21, 24, and 27 days after sowing). The treatments significantly influenced the number of leaves, total leaf area, aerial part fresh mass, root fresh mass, and total fresh mass and dry mass (p<0.01), as well as plant height and stem diameter at 5% probability level by the ‘F’ test. The concentration of 1.6% was the one that showed the best performance for the increase in leaves, plant height, total leaf area, stem diameter, and fresh and dry phytomass of melon seedlings. The most significant accumulation of fresh and dry mass in the seedlings was obtained at the concentration of 1.6% of Chlorella sp.