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Article

Conventional and Nano-Zinc Foliar Spray Strategies to Improve the Physico-Chemical Properties and Nutritional and Antioxidant Compounds of Timor Mango Fruits under Abiotic Stress

by
Mahmoud Abdel-Sattar
*,
Essa Makhasha
and
Rashid S. Al-Obeed
Department of Plant Production, College of Food and Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia
*
Author to whom correspondence should be addressed.
Horticulturae 2024, 10(10), 1096; https://doi.org/10.3390/horticulturae10101096
Submission received: 26 September 2024 / Revised: 12 October 2024 / Accepted: 13 October 2024 / Published: 15 October 2024
(This article belongs to the Section Biotic and Abiotic Stress)
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Abstract

Zinc deficiency is common under heat stress, and further research is needed to determine how to enhance the fruit quality of mango trees through the use of three forms of zinc, namely Zn-NPs, zinc sulfate (ZnSO4), and chelated zinc (Zn-chelated), as a foliar spray. This research was carried out using ten treatments to investigate the effect of zinc forms on the fruit quality of Timor mango trees. With a few notable exceptions, every fruit quality measurement (physical characteristics, chemical properties, mineral contents, and antioxidant compounds) responded to every treatment looked into; however, the extent of the reaction differed depending on the fruiting measurement. Furthermore, the Zn-NPs created a larger difference in the fruiting measurements than the ZnSO4 and Zn-chelated forms. ZnO NPs at 100 ppm ranked first, followed by ZnO NPs in the first spray and zinc EDTA in the second spray, followed by ZnO NPs in the first spray and ZnSO4 in the second, for all mineral content and antioxidant compound measurements and most of the fruit physico-chemical characteristics. In contrast, the lowest levels of minerals and antioxidant compounds and most of the fruit physico-chemical characteristics were found in the controls. The outcomes of the other treatments after the three treatments lay somewhere between these two extremes, and this pattern was detected throughout two seasons. Spraying Timor mango trees with nano, chelated, and sulfate zinc can be considered a safe and environmentally friendly natural method for improving fruit quality in abiotic stress regions.

1. Introduction

The mango (Mangifera indica L.), a kind of evergreen plant, is a member of the Anacardiaceae family’s Mangifera genus [1] and is one of the most important fruit crops grown in the subtropical and tropical and regions of Asia, Australia, Africa, and Latin America [2,3]. Mango has significant economic value on a global scale due to its nutritional, functional, and sensory qualities [4,5]. This has been attributed to its mineral content, bioactive compounds like carotenoids and phenolic compounds, plant pigments, and abundance of vitamin C, carbohydrates, amino acids, dietary fiber, and organic acids [6,7]. In addition, mango combines sweetness and aroma with significant nutritional value [8].
Mango farming has been practiced in Wadi Jizan, Saudi Arabia, for around forty years [9]. A desert region bordering the Red Sea in Saudi Arabia’s southwest is known as Jizan Province. Jizan has a hot desert climate, with summer highs of 38.5 °C and winter highs of 30 °C on average. In July, the lowest average temperature is 29 °C, and in winter, it is 21 °C [10]. The weather is very hot all year round, and the average annual temperature is above 30 °C, making this one of the hottest places in the world. In addition, in recent years, the Jizan region has faced the development of certain environmental problems as a result of climate change and other processes [10]. Mango trees grown under the conditions of the Jizan region suffer from a decline in fruit production and quality, especially for the Timor cultivar, because of the negative consequences of unfavorable environmental circumstances.
Abiotic stresses due to extreme elevation or lowering of the temperature are among the most severe environmental stresses, affecting almost all plant functions, including fruit development and ripening, and thus causing serious declines in crop yield and quality [11]. Heat stress can result from severe temperature changes (10–15 °C above or below the ideal) [12]. Temperature stress includes extreme elevation or lowering of the temperature. Increased temperatures change membrane fluidity, damage photosynthetic machinery, and disturb the overall stability of metabolic systems, leading to the overproduction of reactive oxygen species (ROS) and oxidative stress, which leads to cell death [12,13,14]. Heat stress in plants reduces photosynthesis, chlorophyll content, enzymatic activity, transpiration rate, stomatal conductance, membrane stability index, and antioxidant levels, while increasing reactive oxygen species (ROS) production [15]. Heat stress causes the accumulation of antioxidative enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase (POD), which results in an elevated amount of ROS in plants [16,17]. Ultimately, it poses major threats to crop growth, productivity, and fruit quality [18].
One of the biggest problems for global agricultural output and food security is abiotic stress in plants. The current trends are not favorable to mango production, and adaptation will be necessary. Therefore, new strategies must be developed. This adaptation must involve specific and urgent research to improve the nutritional status, induce flowering, increase yield, and improve fruit quality at high temperatures. One example of a strategy to achieve this is the use of foliar sprays with zinc. Under high-temperature conditions, the foliar application of zinc improves morpho-physiological and enzymatic antioxidant defense mechanisms [19]. Therefore, the foliar spray strategy may improve the nutritional value of food crops, along with their tolerance to environmental conditions [11], ensuring quality fruit production and sustainability.
Zinc is an important element in plant nutrition because it plays an important role in the structure and growth of plants by functioning as a cofactor for the action of 300 enzymes [20]. Zinc enhances agricultural productivity, improves crop quality, and ensures crop sustainability [21]. Zinc regulates the enzyme carbonic anhydrase for carbohydrate fixation in plants and promotion of the metabolism of carbohydrates, proteins, and auxin, as well as protection from oxidative stress via SOD. It also suppresses the production of hydroxyl radicals in the thylakoid lamellae [22]. Zinc is involved in many important functions of plants, including improving plant resistance to abiotic stress by reducing oxidative damage and improving nutrient uptake and growth [23]. Furthermore, Zn is the structural cofactor of the zinc finger proteins, which operate as essential transcriptional regulators in plant defense and acclimatization responses to stress [24]. Zinc has a critical role in limiting the harmful effects of heat stress by maintaining the structural integrity of proteins, membrane lipids, numerous cell components, and DNA. It also facilitates ion transport in plants [25,26]. Zinc feeding improves defense against heat stress by preserving membrane integrity within the plant system [27]. There is a need for an effective strategy to enhance growth, yield, and fruit quality through the foliar application of ZnSO4, Zn chelates, and zinc oxide nanoparticles [9]. There are several types of zinc fertilizers, but the most often used ones worldwide include chelates, zinc oxide (ZnO), and zinc sulfate (ZnSO4) [28]. Nanotechnology has emerged as a novel technique for improving crop productivity by utilizing nanoscale products such as nano fertilizers [29]. Many prospective strategies for improving plants’ abiotic stress tolerance are being researched, including using nanoparticles, which have been demonstrated to favorably influence plant performance under stress conditions [30].
Although there is a systematic study available regarding the most effective method for ameliorating zinc deficiency using different sources of zinc and their application on the nutritional status and productivity of mangoes [9], no systematic study is available regarding the effects of different zinc formulations (salts, chelates, and nanoparticles of zinc oxide) on improving the fruit quality of the Timor mango in semi-arid conditions. Therefore, this study was conducted to assess the effect of traditional zinc and ZnO NP formulations to maximize zinc use efficiency in enhancing the physical and chemical characteristics of the fruits and the nutritional and antioxidant compounds of Timor mangoes grown under abiotic stress.

2. Materials and Methods

2.1. Experimental Site and Plant Materials

The present study was conducted using eight-year-old Timor mango trees (Mangifera indica L.) budded on Kutchineer seedling rootstocks. The trees were cultivated in sandy soil, spaced 2 × 4 m apart, through two successive seasons of 2022 and 2023, in a private orchard in the Jizan region, Kingdom of Saudi Arabia (GPS coordinates: 17°00′54″ N, 42°51′03″ E). The changes in monthly air temperature and relative humidity at the study site during the seasons of 2012, 2013, 2022, and 2023 are shown in Table 1. Trees were irrigated with well water under a drip irrigation system with two lines and drippers (4 L/h) along the lines. The mango trees were grown under routine cultural practices based on recommendations of the Ministry of Environment, Water, and Agriculture, Saudi Arabia. Soil properties of the experimental site at the beginning of the study are presented in Table 2. The studied mango trees were almost identical in health, size, vigor, uniformity, and productivity, and were free of defects following the application of conventional agricultural practices, such as pruning, irrigation, and management of diseases, pests, and weeds. Thirty healthy trees with as consistent growth and vigor as possible were included in the experiment. The trees were exposed to ten treatments, with three replicates for each treatment (one tree per replicate), in a randomized complete block design (RCBD), following the directions of Snedecor and Cochran [31]. The chosen trees were sprayed with three forms of zinc, namely zinc sulfate (ZnSO4), chelated zinc (Zn-chelated), and zinc oxide nanoparticles (ZnO NPs), at concentrations of 0.1% (w/v), 0.2% (w/v), and 100 ppm, respectively, on January 7 and then 4 weeks after the first spray using ten spray treatments. The zinc oxide nanoparticles were produced by Stem Chemical, 7 Muliken Way, Newburyport, MA, USA. The Piosol Zn (chelated with lignosulfonates) was produced by Pioneers Chemicals Factory, Riyadh, Saudi Arabia. The zinc sulfate (Zn 21%) was manufactured by Karnataka AgroChemicals, Bangalore. The trees were sprayed until run-off with a manual pressure sprayer, and Bio New film (made by Misr El-Dawliya) was added as a surfactant agent at 60 mL/100 L water to all spray treatments, including the control, to obtain good coverage and penetration.
The selected trees were separated into ten different treatments, counting the control, as follows: T1, control (water spray); T2, nano-zinc in the first spray and second spray; T3, chelated zinc in the first spray and second spray; T4, zinc sulfate in the first spray and second spray; T5, nano-zinc in the first application and chelated zinc in the second application; T6, nano-zinc in the first application and zinc sulfate in the second application; T7, chelated zinc in the first application and nano-zinc in the second application; T8, chelated zinc in the first application and zinc sulfate in the second application; T9, zinc sulfate in the first application and nano-zinc in the second application; and T10, zinc sulfate in the first application and chelated zinc in the second application. The zinc oxide nanoparticles were produced by Stem Chemical, 7 Muliken Way, Newburyport, MA, USA.

2.2. Measurements and Determinations

At harvest, fully mature fruits (gray pedicel, green peel, and soft in the touch) from each replicate were collected to measure the fruit quality parameters. A random sample of 32 ripe fruits from each tree per replication was selected.

2.2.1. Fruit Physical Measurements

Half of the fruits were examined to determine their physical characteristics. A digital scale was used to determine the fruit, peel, seed, and pulp weight (g) (Mettler, Toledo, Switzerland, 0.0001 g accuracy). Utilizing a 0.01 mm sensitive digital caliper (Mitutoyo, Kawasaki, Japan), fruit width and fruit length (in cm) were measured, and the fruit shape index (length/width) was estimated. In addition, fruit firmness (Ib/Inch2) was determined using a Magness–Taylor pressure tester (8 mm) “plunger” on opposite sides of the flesh of each fruit after peeling.

2.2.2. Chemical Properties and Nutritional and Antioxidant Compound Measurements

The remaining samples of fruits from each replicate were randomly selected to determine the chemical properties and nutritional and antioxidant compounds. The moisture content of mango juice samples was determined in triplicate according to the AOAC [32] method, by drying about 5.0 g sample at 105 °C overnight. The moisture content was expressed as a percentage.
Moisture (%) = Weight of fresh sample − weight of dry sample/weight of fresh sample × 100.
The fruit pulp was pressed and mixed with the fruit juice to assess the remaining chemical qualities of the fruit. The total soluble solids (TSS) content was calculated using an Abbe refractometer (TAGO 9099, Tokyo, Japan), with a drop of a well-mixed sample placed on its prism. A direct refractometer reading was obtained and recorded in °Brix. The titratable acidity of the mango samples was calculated as citric acid/100 mL of juice by placing a 10 mL juice sample in a 250 mL beaker and adding 40 mL of water. This was thoroughly mixed, and then three drops of phenolphthalein indicator were added to the juice water solution. The solution was titrated with the standard 0.1 M NaOH, and acidity was estimated according to the AOAC [32]. Then, the TSS/acidity ratio was calculated.
Nutritional compounds were evaluated by the determination of the total sugar contents, reducing sugar contents, non-reducing sugar contents, and mineral content in the fruits of the Timor mango during this study. The total and reducing sugar contents were analyzed by using Miller’s method [33], using a 10 mg sample mixed with 5 mL of H2SO4 (5%) at room temperature. After the tube was closed, it was heated in a water bath at 105 °C for 2.5 h with shaking once every 0.5 h, followed by cooling. Then, the pH was adjusted to 7 using NaOH. To determine the total sugar, a 0.5 mL sample solution was mixed with DNS reagents (1 mL), and the mixture was heated in boiling water (100 °C) for 10 min. Following this, 1 mL of 40% potassium sodium tartrate (Rochelle salt) solution was added. After cooling, the solution was adjusted to 10 mL using deionized water, and then the absorbance was measured in a spectrophotometer at 540 nm. To determine the reducing sugars, a 0.5 mL sample solution was mixed with 1 mL of 3,5-Dinitrosalicylic Acid (DNS) reagent. The mixture was boiled in boiling water (100 °C) for 10 min. Following this, a 1 mL solution of 40% potassium sodium tartrate (Rochelle salt) was introduced. After cooling, the solution was adjusted to 10 mL using deionized water, and then at 540 nm, the absorbance was determined with a spectrophotometer. The difference in these numbers was used to compute the percentage of non-reducing sugars.
The mineral contents of the fruit pulp were analyzed using the wet digestion method, following Jacob’s method [34] with slight modification. The dried mango pulp sample (0.5 g) was digested by heating in a Kjeldahl flask with 5 concentrated sulfuric acid and 3 mL 30% hydrogen peroxide for each sample. A blank was created by heating the same amount of sulfuric acid and hydrogen peroxide to 450 °C until all organic content was oxidized. This condition was reached when the solution did not darken further with continuous heating and a clear solution was obtained. This solution was cooled and diluted to 100 mL for the estimation of the macro- and micronutrients. The micro-Kjeldahl method was used to estimate the phosphorus (P) and nitrogen (N) contents (%) of the digested solution, and a spectrophotometer (9100UV-VIS, Manufacturer: PerkinElmer, Woodbridge, ON, Canada) was used to determine the total P and N content colorimetrically. The potassium (K) and nickel (Ni) contents were determined by flame photometry (A&E-FP8501, A&E Lab (UK) Co., Ltd., London, UK). A Perkin Elmer 2380 Atomic Absorption Spectrometer was used to determine the mineral content of sodium (Na). Ionic chromatography plasma (Optical Emission Spectrometer; Perkin Elmer, Ontario, Canada) was used to evaluate the concentrations of iron (Fe), manganese (Mn), calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), and boron (B) using the Donohue and Aho technique [35]. Pulp mineral contents of macroelements N, P, and K were expressed as g·kg−1, while macroelements Ca and Mg and microelements (Fe, Mn, Cu, Zn, Na, Ni, B) were expressed as mg·kg−1.
Antioxidant components in the extracted juice were assessed by measuring vitamin C, total phenol content, total carotenoids, and total antioxidant activity. According to AOAC [32], ascorbic acid (vitamin C) was determined by homogenizing 5 g fruit pulp with 3% metaphosphoric acid (25 mL), which was then filtered through filter paper. To achieve a pink endpoint, a 5 mL filtrate sample was titrated with 2,6-dichloroindophenol dye (standardized by metaphosphoric acid). The results were given on a fresh weight basis (mg ascorbic/100 g). The total phenolic content was assessed using Folin Ciocalteau reagent according to the method published by Slinkard and Singleton [36] at 760 nm using a UV-Vis Spectrophotometer (Laxco-Alpha-1102, Analytik Jena, Germany). It was expressed as milligrams of gallic acid equivalents (GAE)/mL. Total carotenoids were evaluated using the method of Ranganna et al. [37]. After the addition of about 5 g of fruit pulp to 20 mL of acetone, the mixture was left in the dark for ten to fifteen minutes. A sintered funnel was used to filter the contents while being suctioned. To fully extract the pigment, about 20 mL of acetone was applied twice, followed by 20 mL of hexane. After mixing, the solutions were moved to a funnel for separation. The top aqueous layer was entirely removed after five minutes. A 250 mL volumetric flask was used to hold the lower hexane layer. Hexane was added to the flask until it reached the full capacity. After the addition of a small amount of anhydrous sodium sulfate, the absorbance at 450 nm was measured using hexane as a blank. The following equation was used to determine the carotenoid concentration of each sample: weight of the sample × 250 × 1000 × 100/250 × absorbance. The value of total carotenoids was given as µg/100 mL. The free radical scavenging activity was determined via the method of Lee et al. [38], using freshly prepared methanolic DPPH (0.01 mM). Three mango juice extracts were combined with a DPPH solution (2 mL) and a diluted solution (1 mL) of the extract in methanol. Using a UV/VIS Specord 210 plus (Analytik Jena, Germany) spectrophotometer, the reaction mixtures’ decreased purple coloring was measured at 517 nm. The extraction method employed methanol. The experiment was run in duplicate. The free radical scavenging activity (RSA) of the mango juice extracts was determined using the following formula: RSA (%) =1 − A1/A0 × 100, where A0 and A1 are the absorbance values of the control and sample extract, respectively.

2.3. Statistical Analysis

This experiment consisted of 10 treatments arranged in a randomized complete block design (RCBD), as outlined by Gomez and Gomez [39], with three replicates for each treatment and one tree for each replicate. Snedecor and Cochran [31] conducted a variance analysis on the data obtained over two seasons. Significant differences in the means of the different treatments were also distinguished using the least significant difference (L.S.D) method at 0.05 probability using the Statistical Analysis System (SAS) version 9.13 [40].

3. Results

The results revealed that, in both seasons, the recorded fruit quality parameters were all favorably influenced by the chelated (Zn-chelated), sulfate (ZnSO4), and zinc oxide nanoparticle (ZnO NP) treatments. Furthermore, the data recorded for the individual parameters revealed substantial increases when the trees were sprayed with ZnO NPs at 100 ppm on two occasions, namely 7 January and then 4 weeks after the first application. The investigated fruit quality parameters were the physical and chemical characteristics and the nutritional and antioxidant compounds.

3.1. Physical Characteristics

The data obtained for the fruit weight (g), peel weight (g), seed weight (g), pulp weight (g), pulp/fruit ratio, fruit length (cm), fruit width (cm), fruit shape index, and fruit firmness (Ib/Inch2) represented the physical characteristic parameters measured for their response to different sources of zinc (chelates, salts, and ZnO NPs). Their combinations during the 2022 and 2023 seasons are presented in Table 3. The data clearly showed that in both seasons, all the recorded physical property parameters were positively affected in the fruits of trees sprayed with different zinc forms. In general, ZnO NPs at 100 ppm, zinc sulfate at a concentration of 0.1% (w/v), chelated zinc at a concentration of 0.2% (w/v), and their combinations significantly improved all fruit physical properties compared with the control (water spray). The only exception was the pulp/fruit ratio, whose trend showed the opposite effect. The highest values were measured in the trees sprayed with nano-zinc in the first spray and second spray treatment, followed by trees sprayed with nano-zinc in the first application and chelated zinc in the second application. There were insignificant differences in the fruits of trees sprayed with nano-zinc, chelated zinc, zinc sulfate, and their combinations in the pulp/fruit ratio and shape index ratio.

3.2. Chemical Characteristics

The moisture content (%), pH, TSS (%), acidity (%), TSS/acidity ratio, total sugars (%), reducing sugars (%), and non-reducing sugars (%) of Timor mango fruits were influenced by the different forms of zinc and their combinations. Figure 1A–D and Figure 2A–D show the data collected during the experimental seasons of 2022 and 2023. Zinc treatments led to the highest values for total soluble solids (TSS), pH, TSS/acidity ratio, total sugars (%), and non-reducing sugars (%), while the lowest values were obtained for moisture content (%), acidity, and reducing sugars (%). High values for the total sugars (%), non-reducing sugars (%), pH, total soluble solids (TSS), and TSS/acidity ratio were recorded when the trees were sprayed with nano-zinc in the first and second sprays, while the lowest values were obtained in the control treatment. This trend was observed for all fruit chemical characteristics during the 2022 and 2023 experimental seasons. Other combinations of zinc treatment gave values in the middle. The results showed that treatments with higher pH have lower acidity; the lower the pH, the higher the acidity in fresh fruit.

3.3. Mineral Contents

Regarding the impact of different forms and concentrations of zinc and their interaction with the macro- and micronutrient contents of Timor mango fruit pulp, the data in Table 4 and Table 5 revealed that all forms of zinc significantly increased the fruit mineral content of Timor mango fruits compared with the control. The data reported in the same tables demonstrated that the different forms and concentrations varied in terms of their impact on the fruit mineral compositions of the Timor mango fruits. However, the most effective was generally the nano form of zinc. The highest mineral content in the fruits was significantly associated with zinc oxide nanoparticles (ZnO NPs) at concentrations of 100 ppm. Furthermore, the response direction was significantly or slightly associated, varying from one fruit mineral component to another, when other forms of zinc were combined with the nano form. Conversely, the lowest values for all or most of the mineral contents of the fruits were found in the control. The other forms of zinc, whether chelate or sulfate, have values in the middle of the two extremes. The mineral contents of the fruit pulp could be arranged in descending order: ZnO NPs in the first spray and second spray; ZnO NPs in the first application and zinc EDTA in the second application; ZnO NPs in the first application and ZnSO4 in the second application; zinc EDTA in the first application and ZnO NPs in the second application; zinc EDTA in the first spray and second spray; zinc EDTA in the first application and ZnSO4 in the second application; ZnSO4 in the first application and ZnO NPs in the second application; ZnSO4 in the first application and zinc EDTA in the second application; ZnSO4 in the first spray and second spray; and control treatment.

3.4. Antioxidant Compounds and Activities

The data presented in Figure 3A–D indicated that the vitamin C (mg/100 mL juice), antioxidant activity (DPPH inhibition, %), total carotenoids (µg/100 mL), and total phenolic content (TPC, mg GAE/mL) were influenced by specific and interaction effects of different concentrations of nano-zinc, chelated zinc, zinc sulfate, and their combinations during the 2022 and 2023 seasons. The grade of response varied amongst antioxidant compound parameters. In addition, the rates of variation in the measurements that ZnO NPs at 100 ppm displayed were more marked than the rates of correlation generated by zinc sulfate (ZnSO4, 21% Zn) at 0.1% (w/v) and chelated zinc (zinc EDTA, 12% Zn) at 0.2% (w/v). The control trees recorded the lowest values of the antioxidant compounds in both seasons. The results presented the superiority of the antioxidant compounds in fruits among trees sprayed with nano-zinc in the first spray and second spray treatment, followed by the fruit of trees sprayed with nano-zinc in the first application and chelated zinc in the second application, compared with the rest of the treatments. The obtained data showed that the fruit of trees sprayed with two applications of ZnO NPs had the highest values for antioxidant activity (DPPH inhibition), total phenolic content (TPC), vitamin C, and total carotenoids at 84.15 (%), 48.56 mg GAE/mL, 37.17 mg/100 mL juice, and 8763.00 µg/100 mL, respectively, in the 2022 season. In the 2023 season, the values were 84.58%, 48.80 GAE/mL, 36.85 mg/100 mL juice, and 8874.00 µg/100 mL, respectively. The lowest values were recorded in the control treatment and were 24.41 mg GAE/mL, 50.5%, 26.78 mg/100 mL juice, and 4136.00 µg/100 mL, respectively, in the 2022 season. In the 2023 season, the values were 25.14 GAE/mL, 50.38%, 26.45 mg/100 mL juice, and 4922.00 µg/100 mL, respectively.

4. Discussion

Some of the important components that contribute to the acceptability of high-quality fresh mango by customers are its flavor, texture, chemical composition, and antioxidant characteristics [41]. Flavor (aroma and taste) is a significant attribute that is mostly composed of sweetness, sourness, and aroma, correlating to sugars, acids, and volatile chemicals and, to a large extent, decides the consumer acceptance of the fruit [42]. Consumers are also becoming increasingly interested in the nutritional value of fruit. As antioxidant compounds can have positive preventative effects on human health, dietitians advise preserving these components, and consumer preferences emphasize focusing on compounds that promote health [43]. The growing focus on fruit quality calls for further research to better characterize the physical–chemical, nutritional, and biologically active compounds of mango fruits.
The increasing concentration of anthropogenic greenhouse gases is probably the primary cause of the reality that is becoming known as climate change [44]. Climate variability and the frequency of extreme occurrences (heavy rainfall, scorching heat, drought, hurricanes) are also predicted to increase. Climate change significantly affects plant growth, productivity, fruit quality, and the nutritional value of fruit by causing different abiotic and biotic stresses to plants. Abiotic stresses, including cold, heat, drought, heavy metals, and salinity stress, can lead to significant losses in crop growth and productivity [17] of up to 50% of the total major productivity [45,46]. Temperature extremes, among other abiotic factors, contribute to significant crop output losses in various parts of the world, resulting in food poverty [30]. Climate changes due to high temperatures result in vigorous vegetative growth and low nutritional status in mangoes, and in winter, early flowering can cause low yields [44] and ultimately low productivity and fruit quality. Due to changing climatic conditions, tropic and subtropic areas of the world are facing many challenges in relation to mango productivity [44,47]. Every stage of the mango phenological cycle (flowering, vegetative growth/rest, fruit growth, and harvest/vegetative growth) may be influenced by a change in precipitation, humidity, temperature, light, and greenhouse gases [48]. Climate change is therefore a serious concern for agriculture, including in the Jizan region of the Kingdom of Saudi Arabia, and adaptation will be necessary to sustain productivity and quality. Many prospective strategies are being researched to improve the abiotic stress tolerance of plants, including the use of nanoparticles, which have been demonstrated to have a favorable influence on plant performance under stress circumstances [29]. Nanotechnology offers a potential solution for reducing the overuse of fertilizers due to its high surface area, rapid diffusion, and impact on enhanced plant growth and productivity and in this way could improve sustainable agricultural practices [49].
Reactive oxygen species (ROS) are generated during abiotic stress [50,51]. Zn has been found to boost plant resilience to abiotic stress by reducing oxidative damage, resulting in improved nutrient uptake and plant development [52]. Furthermore, zinc serves as a structural cofactor for zinc finger proteins (ZFPs), which are crucial transcriptional regulators involved in plant defense and stress adaptation [14]. Zn-superoxide dismutase scavenges reactive oxygen species by converting them into H2O2 and eventually to water via catalase, thus providing a defensive strategy for plants under abiotic stress [53]. Zn is an essential component of plant enzymes such as alcohol dehydrogenase (ADH), carbonic anhydrase, alkaline phosphatase, phospholipase, RNA polymerase, and Cu-Zn SOD. It is also a significant component of many proteins involved in DNA and RNA synthesis [26,27]. Under drought stress, an adequate zinc supply regulates membrane permeability and antioxidant activity, as well as improving photosynthesis, nutrient uptake, membrane stability, and the plant–water connection [54]. Furthermore, Zn application contributes to a significant increase in leaf area, enhancement in photosynthetic pigments such as chlorophyll, and an increase in relative leaf water content, stomatal conductance, and osmolyte accumulation, resulting in improved vegetative growth, yield, and protection of leaf tissues from the damaging effects of abiotic stress [55].
The increase in fruit quality measurements with zinc treatment is likely due to its effect on improving tree growth, which includes leaf nitrogen, phosphorus, potassium, calcium, copper, magnesium, iron, copper, and zinc contents (%), the total chlorophyll, total carotenoid, and total carbohydrate contents of the leaves, the absorption of water and nutrition, and an increase in the synthesized food that is translocated to the fruits [9]. Zn application enhances membrane stability, nutrient uptake, the plant–water relationship, photosynthetic performance, osmolyte accumulation, antioxidant activities, and gene expression. It improves the synthesis of photosynthetic pigments, photosystem activities, and enzymatic activities, as well as maintaining the structure of the photosynthetic apparatus, ensuring greater growth under abiotic stress [54]. Due to the preliminary improvement of vegetative growth and photosynthesis in response to the application of different zinc forms (nano, sulfate, and chelated), the fruit improved significantly. Furthermore, zinc nanoparticles improved plant stability under drought stress and compensated for the negative effects of abiotic stress. The highest values for the fruit quality parameters were substantially associated with Timor mango trees that received Zn-NPs. Because of their wide surface area, ease of attachment, and quick mass transfer, nanoparticles are advantageous in the administration of agrochemicals [56,57]. Moreover, Kah [58] found that the efficacy of nano-agrochemicals can outperform traditional products by up to 30%. Nano fertilizers (NFs) are effective when used in smaller amounts than traditional fertilizers [59,60]. Compared to the nano and chelated forms, the mineral form of zinc (ZnSO4) had the lowest values for the growth and fruit yield criteria due to its reduced absorption and efficiency [61].

4.1. Physical Characteristics

In general, all of the measured physical characteristics were significantly affected by spraying with different forms of zinc in both the 2022 and 2023 seasons (Table 3). An increase in fruit dimensions (i.e., diameter and length) and weight occurred following the application of the three forms of zinc: zinc sulfate (ZnSO4), chelated (Zn-chelated), and zinc oxide nanoparticles (ZnO NPs). In most circumstances, the fruit weight is not a determining factor of quality; yet, customers prefer medium-sized fruits. The increase in fruit length, diameter, and volume detected in this study after zinc treatment might have been because zinc plays an indirect role in activating protein biosynthesis and RNA/DNA mechanisms, regulating several enzyme activities included in biochemical pathways, such as carbohydrate metabolism, protein metabolism, and growth regulator metabolism, which increase cell division, cell expansion, and the rate of fruit growth [62,63]. The increases in cell division and elongation explain the increase in fruit size due to the zinc treatments. Fruit also develops larger when its cells—which are the building blocks of its mass—are more efficient because these cells can draw in more water, minerals, and carbohydrates. Our findings confirmed those of Maklad et al. [64] on the Ewais mango cultivar. Zinc is necessary for the formation of auxin, the hormone in plants that causes cells to elongate and grow [65]. Because zinc plays an important role in enhancing the amount of micro- and macrominerals, total chlorophyll, total carotenoids, and total carbohydrates in leaves, it produces more photoassimilates and partitions than efficiently into the harvested organ (fruits), increasing the length, width, and size of the fruits, as well as their number [9]. The ZnSO4, Zn-chelated, and ZnO NP treatments resulted in fruit that was less firm than the untreated control. The firmness loss could be attributed to the progressive breakdown of proto-pectin into lower-molecular-weight fractions that are extra soluble in water, which has been demonstrated to be directly connected with the pace of fruit softening. Trees sprayed with zinc may maintain fruit firmness and increase fruit flesh firmness via decreased rates of ethylene generation and respiration and decreased ACC oxidase activity, in addition to decreasing the effects of ethylene-induced enzyme activity, such as polygalacturonase and pectin production [66].

4.2. Chemical Characteristics

The chemical characteristics of the fruit, as indicated in Figure 1A–D and Figure 2A–D, showed that the total soluble solids, pH, total soluble solids/acidity ratio, non-reducing sugars (%), and total sugars (%) were increased, whereas the acidity, moisture content (%), and reducing sugars (%) were decreased due to zinc’s role in carbohydrate metabolism in enhancing photosynthesis and sugar conversion [67] and in the synthesis and transference of proteins and carbohydrates [68]. The data showed that the total soluble solids (%), total soluble solids/acidity ratio, total sugars (%), and non-reducing sugars (%) of the fruit were significantly improved during both seasons for all zinc treatments compared to the untreated control (Figure 1B,D and Figure 2B,D). In the presence of zinc, the functioning of some enzymes may be improved, affecting physiological processes, which in turn hydrolyze starch and support metabolic activity during the change of available starch into TSS and sugars. A popular indicator of ripeness and taste is the TSS/acidity ratio; the higher the ratio, the sweeter the fruit. In addition, the fruit pulp’s pH has a significant impact on both flavor and preservation [69]. Sugars are the primary substrate for the plant’s defensive response, hormone signaling molecules, and immune system regulation [70]. For the majority of fruit species, the maturity index, also known as the TSS/titratable acidity ratio, is a more reliable measure of flavor quality and taste from the consumer’s point of view than the individual amounts of acids or sugars [43]. The reduction in fruit juice total acidity caused by the various zinc forms and concentration combinations is typically associated with late fruit maturity [56]. The moisture content of unripe fruits is lower and increases during the ripening period until it reaches its maximum at the end of the season. Zinc is essential for maintaining phospholipid and membrane protein structural alignment and ion transport networks. It also plays a major function in preserving membrane structure [71]. High temperatures and softening or faster ripening of the fruits limit their storage, packaging, and transport [72]. Therefore, the treatment of mango trees by spraying with different forms of zinc may maintain their quality, confer a longer marketing period, and increase access to international markets.

4.3. Mineral Contents

The contents of mineral elements and heavy metals in the fruits are given in Table 4 and Table 5. These results showed that zinc may play a role in improving macro- and micromineral concentrations in the fruit of Timor mangoes grown in two successive seasons. However, differences in mineral content are affected by various factors, including the species, cultivar, ability to absorb nutrients, root systems, growing habitat, and the structure of the medium in which the plant is grown [73]. Spraying zinc on tree leaves improves the nutritional value of food crops, as reported by Abdul Sattar et al. [11]. Mangoes provide potassium, calcium, magnesium, manganese, copper, iron, phosphorus, sodium, and zinc in the human diet (Table 4 and Table 5) [74,75]. Although mango fruits are rich in mineral nutrients that are essential to human health, because national and international standards set a maximum permitted level of heavy metals in the human diet, food concentrations of heavy metals are an important aspect of food quality. The heavy metal content in the edible part of the fruit is shown in Table 5. In general, the fruits of trees treated with different forms of zinc had moderate levels, within the recommended level set by the USDA [75] and Yahia et al. [76]. These heavy metals are dangerous and toxic to health if they are ingested more than the permissible limit. ZnO NPs play an important role in reducing heavy metal uptake in various plant species [77]. Heavy metals may be present because of the disposal of solid waste onto land that has a high concentration of heavy metals, or because of the utilization of arsenic-contaminated water during farming. As a result, heavy metals may be present in groundwater, which plants may use and eventually absorb into their fruits [78].

4.4. Antioxidant Compounds and Activities

Antioxidants are compounds capable of reducing oxidative damage produced by free radicals, including polyphenols, vitamins, and carotenoids, which bestow health-promoting effects on mangoes [79,80,81]. Vitamin C is a hydrophilic vitamin found in many fruits as oxidized L-dehydroascorbic and L-ascorbic acid. L-ascorbic acid is the most physiologically active form of vitamin C and is a potent antioxidant because of its ability to neutralize superoxide radicals and trap hydroxyl [82]. Polyphenols are the most important antioxidant micronutrient in the food matrix, and they can be considered a primary signal for selecting any plant product as a natural source of antioxidants in functional foods [83]. Carotenoids are lipophilic antioxidants abundant in tropical fruit species such as mangoes [84] and are used as colorants and antioxidant preservatives in the food industry [85]. The abundance of antioxidant compounds and activities in tropical fruits such as mangoes is associated with variations in the expression of genes involved in carotenoid biosynthesis pathways, in response to environmental stimuli such as light signaling cascades and photo-oxidative stress [86]. Among the bioactive substances that we assessed in mango fruits, vitamin C (mg/100 mL juice), total phenolic content (TPC, mg GAE/mL), total carotenoids (µg/100 mL), and antioxidant activity (DPPH inhibition, %) showed a significant increase following Zn application. The metabolic function of zinc, which includes controlling the metabolism of carbohydrates, producing proteins, and activating certain antioxidant enzymes that prevent oxidative and peroxidative cell damage, may be linked to this increase [62,87]. By preserving active antioxidants and interacting with other cellular metabolites and environmental factors, zinc can also modulate the activity of antioxidant enzymes and boost plant tolerance to abiotic stress. This leads to positive effects on antioxidant compounds. Subcellular organelles containing NPs can cause oxidative stress signaling cascades in cells. Organisms employ antioxidant defense mechanisms, such as the creation of phenolic compounds, to counteract elevated amounts of reactive oxygen species [88,89]. ZnO nanoparticles are a promising method for the management of abiotic stress in plants because of their ability to affect the expression of stress resistance genes, transcription factors, and enhanced antioxidant activity, which play a role in reducing cellular damage. These strategies offer new approaches to improve crop productivity, enhance stress tolerance, and support sustainable agriculture [77,90,91].

5. Conclusions

The present study found that the foliar spraying of Timor mango trees grown under heat stress with zinc oxide nanoparticles, zinc sulfate, and chelated zinc is a beneficial method for improving fruit quality. The application of nanoparticles (NPs) enhanced the physico-chemical properties, nutritional compounds, and antioxidants of mango fruits under heat stress when compared with conventional cultivation. The effect of foliar nano-zinc (Zn-NPs) as a replacement for conventional zinc on the quality of mango fruits in heat-stressed areas was demonstrated, along with the appropriate concentrations. It was found that spraying mango trees with ZnO NPs (zinc oxide nanoparticles) at 100 ppm on 7 January and 4 weeks after the first application was the best treatment for enhancing mango fruit quality in heat-stressed areas.

Author Contributions

Conceptualization, M.A.-S. and E.M.; methodology, M.A.-S. and E.M.; software, M.A.-S., R.S.A.-O. and E.M.; validation, M.A.-S. and R.S.A.-O.; formal analysis, M.A.-S. and E.M.; investigation, M.A.-S. and E.M.; resources, M.A.-S., E.M. and R.S.A.-O.; data curation, M.A.-S. and E.M.; writing—original draft preparation, M.A.-S., R.S.A.-O. and E.M.; writing—review and editing, M.A.-S., R.S.A.-O. and E.M.; visualization, M.A.-S. and R.S.A.-O.; supervision, M.A.-S.; project administration, M.A.-S. and E.M.; funding acquisition, M.A.-S. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Researchers Supporting Project (number: RSPD2024R707), King Saud University, Riyadh, Saudi Arabia.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

The authors extend their appreciation to the Researchers Supporting Project (number: RSPD2024R707), King Saud University, Riyadh, Saudi Arabia.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Effect of nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on moisture content (%), reducing sugars (%), and non-reducing sugars (%) of mango fruits, cv. Timor, in the 2022 and 2023 seasons.
Figure 1. Effect of nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on moisture content (%), reducing sugars (%), and non-reducing sugars (%) of mango fruits, cv. Timor, in the 2022 and 2023 seasons.
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Figure 2. Effect of spraying with nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on the pH, TSS (%), acidity (%), and TSS/acidity ratio of mango fruits, cv. Timor, in the 2022 and 2023 seasons.
Figure 2. Effect of spraying with nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on the pH, TSS (%), acidity (%), and TSS/acidity ratio of mango fruits, cv. Timor, in the 2022 and 2023 seasons.
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Figure 3. Effect of nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on the antioxidant compounds and activities of mango fruits, cv. Timor, in the 2022 and 2023 seasons.
Figure 3. Effect of nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on the antioxidant compounds and activities of mango fruits, cv. Timor, in the 2022 and 2023 seasons.
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Table 1. Climate characteristics of the Jizan region, Kingdom of Saudi Arabia, in the 2012, 2013, 2022, and 2023 seasons.
Table 1. Climate characteristics of the Jizan region, Kingdom of Saudi Arabia, in the 2012, 2013, 2022, and 2023 seasons.
MonthsRelative Humidity (%)Minimum Temperature (°C)Maximum Temperature (°C)
SeasonSeasonSeason
201220132022202320122013202220232012201320222023
January55.9450.1564.3853.8513.5715.2515.0518.9433.2832.3130.4830.20
February42.7543.0055.4448.4016.1115.6716.9019.7634.7836.6133.6231.95
March43.5643.1944.2548.3318.1219.8919.2121.4937.6436.9137.2232.74
April46.7547.1529.6245.9622.1720.7420.3124.4037.1036.8440.8035.29
May33.4432.0025.7548.3924.8722.8223.6326.0643.5142.4243.5435.90
June27.3825.3131.9449.9025.6825.0225.5526.1244.2142.7044.4437.09
July41.6941.3154.9449.1425.1225.0322.9027.3644.1940.2138.6537.43
August47.0655.3171.8147.1724.8222.2422.2727.5443.2839.6739.0138.28
September33.3535.0046.7533.2623.3724.2622.4927.3741.8742.0540.8641.28
October30.1233.1232.5642.4320.2120.9420.3323.6339.5839.6139.9836.60
November41.6248.1242.4452.5619.5716.6418.8621.1736.4836.9136.4032.87
December53.9448.4449.2539.9417.1714.1015.8718.5932.4933.8733.6531.92
Average41.4741.8445.7646.6120.920.2220.2823.5439.0338.3438.2235.13
Table 2. Physico-chemical analysis of the soil.
Table 2. Physico-chemical analysis of the soil.
pHCaCo3 %EC dS/mO.MTextural classSand %Silt %Clay %
8.0316.701.711.56Sandy loam43.9249.276.81
Nutrients (mg/kg)Soluble anions (meq/L)Soluble cations (meq/L)
PK NHCO3−Cl−SO42−Ca2+Mg2+Na+K+
45.471.856.026.005.16.206.003.005.952.09
Table 3. Influence of zinc foliar sprays with nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on the fruit physical characteristics of mango trees, cv. Timor, during the 2022 and 2023 experimental seasons.
Table 3. Influence of zinc foliar sprays with nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on the fruit physical characteristics of mango trees, cv. Timor, during the 2022 and 2023 experimental seasons.
SeasonTreatmentFruit Weight
(g)		Seed Weight
(g)		Peel Weight
(g)		Pulp Weight
(g)		Pulp/Fruit
Ratio		Fruit Length
(cm)		Fruit Width
(cm)		Fruit
Shape
Index		Fruit Firmness
(Ib/Inch2)
2022T, Control296.00 j25.70 j23.50 j246.80 h0.83 a9.46 j6.06 j1.56 e16.14 j
T2, A + A394.00 a54.55 a41.30 a298.15 a0.76 i13.80 a7.93 a1.74 a18.90 a
T3, B + B359.25 e40.65 e32.03 e286.58 d0.80 e11.42 e7.33 e1.56 e17.49 e
T4, C + C316.50 i28.85 i25.10 i262.55 g0.83 b10.16 i6.55 i1.55 ef16.45 i
T5, A + B384.75 b51.55 b39.35 b293.85 b0.76 h13.20 b7.73 b1.71 b18.43 b
T6, A + C376.75 c47.00 c36.88 c292.88 bc0.78 g12.76 c7.57 c1.69 c18.19 c
T7, B + A367.25 d44.60 d33.93 d288.73 cd0.79 f12.15 d7.41 d1.64 d17.92 d
T8, B + C347.25 f37.65 f29.08 f280.53 e0.81 dc11.21 f7.24 f1.55 ef17.23 f
T9, C + A337.75 g34.25 g28.03 g275.48 f0.82 c10.93 g7.14 g1.54 f17.04 g
T10, C + B330.00 h31.70 h26.45 h271.85 f0.82 bc10.47 h6.93 h1.51 g16.80 h
LSD0.053.861.130.424.220.0060.090.050.0170.05
2023T, Control294.50 j22.60 j24.13 j247.78 g0.84 a9.54 j6.02 j1.59 de16.14 j
T2, A + A386.60 a41.00 a53.10 a292.50 a0.76 h13.88 a7.95 a1.75 a18.90 a
T3, B + B345.75 e32.60 e37.35 e275.80 c0.80 e11.69 e7.35 e1.59 d17.49 e
T4, C + C312.20 i24.28 i25.95 i261.98 f0.84 a10.20 i6.51 i1.57 e16.45 i
T5, A + B372.70 b39.40 b51.03 b282.28 b0.76 h13.17 b7.79 b1.69 b18.43 b
T6, A + C361.25 c37.40 c47.10 c276.75 c0.77 g12.83 c7.54 c1.70 b18.19 c
T7, B + A355.40 d34.15 d41.90 d279.35 bc0.79 f12.23 d7.44 d1.64 c17.92 d
T8, B + C337.15 f30.05 f35.60 f271.50 d0.81 d11.20 f7.25 f1.55 f17.23 f
T9, C + A328.15 g28.55 g31.40 g268.20 de0.82 c10.93 g7.13 g1.53 f17.04 g
T10, C + B321.75 h26.50 h28.40 h266.85 e0.83 b10.62 h6.89 h1.54 f16.80 h
LSD0.053.630.350.683.750.0040.090.060.0200.05
Mean values inside a column for each season followed by various letters are substantially different (p < 0.05).
Table 4. Effect of the sprayed nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on the N, P, K, Ca, and Mg contents of Timor mango fruits in the 2022 and 2023 seasons.
Table 4. Effect of the sprayed nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on the N, P, K, Ca, and Mg contents of Timor mango fruits in the 2022 and 2023 seasons.
TreatmentN (g/kg)P (g/kg)K (g/kg)Ca (mg/kg) Mg (mg/kg)
2022202320222023202220232022202320222023
T, Control6.89 g6.77 j0.78 j0.77 j8.18 j8.24 j0.52 j0.54 j0.85 j0.86 j
T2, A + A11.13 a11.57 a1.65 a1.77 a12.28 a12.12 a1.62 a1.66 a1.95 a1.85 a
T3, B + B9.48 c9.86 e1.28 e1.39 e10.77 e10.86 e1.16 e1.18 e1.36 e1.45 e
T4, C + C8.32 f8.55 i0.83 i0.93 i8.96 i9.17 i0.66 i0.65 i0.94 i1.06 i
T5, A + B10.77 b11.17 b1.51 b1.64 b11.72 b11.84 b1.53 b1.54 b1.85 b1.78 b
T6, A + C10.54 b10.85 c1.47 c1.59 c11.49 c11.68 c1.45 c1.45 c1.74 c1.65 c
T7, B + A9.66 c10.27 d1.33 d1.44 d10.93 d11.17 d1.24 d1.27 d1.55 d1.56 d
T8, B + C9.18 d9.45 f1.14 f1.21 f10.34 f10.45 f0.99 f1.07 f1.26 f1.36 f
T9, C + A8.99 d9.14 g1.03 g1.18 g9.87 g9.93 g0.85 g0.93 g1.16 g1.27 g
T10, C + B8.62 e8.84 h1.00 h1.03 h9.36 h9.57 h0.76 h0.76 h1.05 h1.16 h
LSD0.050.260.050.190.010.030.050.040.030.040.04
Values within a column with the same letter(s) were not significantly different according to LSD (p < 0.05).
Table 5. Effect of the sprayed nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on Cu, Fe, Mn, Zn, Na, B, and Ni contents (mg/kg) of Timor mango fruits in the 2022 and 2023 seasons.
Table 5. Effect of the sprayed nano-zinc (A), chelated zinc (B), and zinc sulfate (C) on Cu, Fe, Mn, Zn, Na, B, and Ni contents (mg/kg) of Timor mango fruits in the 2022 and 2023 seasons.
SeasonTreatmentCuFeMnZnNaBNi
2022T, Control9.62 j15.22 j6.21 j5.25 j0.28 j1.75 j0.67 j
T2, A + A18.61 a34.83 a12.19 a14.35 a1.26 a2.34 a1.55 a
T3, B + B14.37 e25.76 e9.81 e10.80 e0.84 e2.09 e1.14 e
T4, C + C10.24 i17.25 i7.83 i6.91 i0.43 i1.87 i0.73 i
T5, A + B17.84 b32.56 b11.29 b13.68 b1.18 b2.28 b1.45 b
T6, A + C16.42 c30.84 c10.73 c12.84 c1.05 c2.18 c1.35 c
T7, B + A15.86 d28.47 d10.10 d11.50 d0.95 d2.12 d1.26 d
T8, B + C13.84 f23.45 f9.58 f9.63 f0.77 f2.02 f1.03 f
T9, C + A12.28 g21.39 g8.96 g8.50 g0.63 g1.98 g0.96 g
T10, C + B11.88 h19.69 h8.27 h7.45 h0.56 h1.92 h0.84 h
LSD0.050.110.210.080.230.070.020.03
2023T, Control9.66 j16.82 j6.40 j5.77 j0.35 j1.72 j0.67 j
T2, A + A19.83 a36.56 a12.91 a15.14 a1.37 a2.31 a1.53 a
T3, B + B14.61 f26.76 f9.65 f10.89 f0.84 f1.92 f1.05 f
T4, C + C11.71 i19.31 i7.68 i7.44 i0.55 i1.79 i0.75 i
T5, A + B18.58 b34.45 b11.69 b14.41 b1.27 b2.24 b1.47 b
T6, A + C17.27 c32.20 c10.65 c13.91 c1.15 c2.16 c1.36 c
T7, B + A16.08 d30.84 d10.25 d12.78 d1.04 d2.05 d1.25 d
T8, B + C13.42 g24.88 g9.04 g9.38 g0.73 g1.88 g0.96 g
T9, C + A15.93 e28.17 e9.84 e11.30 e0.93 e1.98 e1.16 e
T10, C + B12.16 h21.70 h8.50 h8.23 h0.65 h1.82 h0.86 h
LSD0.050.070.220.080.070.040.030.03
Mean values within a column for each season followed by different letters are significantly different at p ≤ 0.05.
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Abdel-Sattar, M.; Makhasha, E.; Al-Obeed, R.S. Conventional and Nano-Zinc Foliar Spray Strategies to Improve the Physico-Chemical Properties and Nutritional and Antioxidant Compounds of Timor Mango Fruits under Abiotic Stress. Horticulturae 2024, 10, 1096. https://doi.org/10.3390/horticulturae10101096

AMA Style

Abdel-Sattar M, Makhasha E, Al-Obeed RS. Conventional and Nano-Zinc Foliar Spray Strategies to Improve the Physico-Chemical Properties and Nutritional and Antioxidant Compounds of Timor Mango Fruits under Abiotic Stress. Horticulturae. 2024; 10(10):1096. https://doi.org/10.3390/horticulturae10101096

Chicago/Turabian Style

Abdel-Sattar, Mahmoud, Essa Makhasha, and Rashid S. Al-Obeed. 2024. "Conventional and Nano-Zinc Foliar Spray Strategies to Improve the Physico-Chemical Properties and Nutritional and Antioxidant Compounds of Timor Mango Fruits under Abiotic Stress" Horticulturae 10, no. 10: 1096. https://doi.org/10.3390/horticulturae10101096

APA Style

Abdel-Sattar, M., Makhasha, E., & Al-Obeed, R. S. (2024). Conventional and Nano-Zinc Foliar Spray Strategies to Improve the Physico-Chemical Properties and Nutritional and Antioxidant Compounds of Timor Mango Fruits under Abiotic Stress. Horticulturae, 10(10), 1096. https://doi.org/10.3390/horticulturae10101096

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