In an open-field investigation at Quaid-i-Azam University in Islamabad, Pakistan, foliar applications of green-synthesized silver nanoparticles derived from Aloe vera leaf extract enhanced the physiological performance, biomass accumulation, and grain yield of bread wheat across four distinct cultivars. Evaluating three foliar dosages of five, ten, and fifteen parts per million against untreated controls, researchers determined that the fifteen parts per million concentration produced the greatest overall agronomic and physiological responses. The most striking yield improvement occurred in the cultivar Borlaug-16, where individual grain yield expanded from 2.35 grams per plant in control conditions to 6.93 grams per plant under the highest nanoparticle treatment, representing a 194.89 percent increase. Concurrently, biological yield in cultivar Wafaq-23 surged by 94.25 percent, while thousand-kernel weight rose by 12.67 percent in Borlaug-16. These yield enhancements coincided with increased photosynthetic pigments, activated antioxidant enzymes, and improved nitrogen metabolism under field conditions.
Bread wheat, Triticum aestivum, serves as an essential global staple crop, providing nearly twenty percent of the daily calories and protein consumed by the world population. However, modern wheat farming encounters substantial obstacles from climate instability, soil degradation, and declining nutrient-use efficiency. While conventional mineral fertilizers have historically expanded agricultural productivity, extensive portions of applied soil nutrients are regularly lost through environmental runoff, leaching, volatilization, and soil fixation, creating ecological contamination. Agricultural nanotechnology has emerged as a promising strategy to improve resource efficiency, as engineered nanoparticles can modulate plant redox balance and enhance nutrient utilization when delivered at non-toxic levels. However, biological reactions vary substantially depending on particle dimensions, surface chemistry, and delivery pathways. Green synthesis using botanical extracts circumvents hazardous chemicals and high energy consumption associated with conventional nanoparticle production. In this context, Aloe vera leaf extract provides diverse secondary metabolites, such as phenolics and flavonoids, which simultaneously reduce silver ions and stabilize formed nanoparticles.
To synthesize the green nanoparticles, the researchers prepared an aqueous extract by boiling twenty grams of washed, chopped fresh Aloe vera leaves in two hundred and fifty milliliters of distilled water at eighty degrees Celsius for twenty minutes. After cooling, the resulting extract was centrifuged at twelve thousand revolutions per minute for fifteen minutes at four degrees Celsius and filtered through Whatman filter paper. Nanoparticle synthesis proceeded by mixing ten milliliters of this botanical filtrate into ninety milliliters of a one millimolar silver nitrate solution prepared in distilled water. The mixture was incubated overnight in complete darkness at ambient room temperature. Reduction of monovalent silver ions was verified by a visible color shift from a colorless solution to a distinct brownish-yellow suspension. Foliar application of the resulting green-synthesized silver nanoparticles offered a direct route for leaf tissue absorption, avoiding the nutrient immobilization and leaching losses that frequently undermine soil applications.
Physicochemical characterization detailed the structural, optical, and elemental features of the synthesized material. Ultraviolet-visible spectroscopy detected an absorption peak at 269 nanometers, which the authors explicitly noted does not represent the characteristic surface plasmon resonance band of monodisperse metallic silver and likely includes contributions from Aloe vera phytochemicals. Fourier-transform infrared spectroscopy identified absorption bands at 3326, 1640, and 1052 inverse centimeters, indicating that plant-derived hydroxyl, carbonyl, and carbon-oxygen functional groups participated in reducing and capping the particles. Dynamic light scattering documented an average hydrodynamic diameter of 699.6 nanometers with a polydispersity index of 0.591, reflecting particle agglomerations rather than individual primary particles. A zeta potential of negative 2.79 millivolts indicated limited electrostatic stabilization. Scanning electron microscopy confirmed compact, irregularly clustered morphologies, while energy-dispersive X-ray spectroscopy identified silver as the predominant element at 76.01 weight percent. However, X-ray diffraction peaks did not correspond to standard metallic silver reflections, indicating a complex crystalline composite.
Laboratory bioassays evaluated the in vitro antioxidant, antifungal, and antihemolytic properties of the synthesized nanoparticles prior to field administration. In DPPH radical scavenging assays, antioxidant activity increased in a concentration-dependent manner from 8.14 percent at twenty micrograms per milliliter to 27.87 percent at one hundred micrograms per milliliter. Total antioxidant capacity measured by phosphomolybdenum assays similarly climbed from 83.16 percent to 138.42 percent across the same range, demonstrating chemical reducing potential attributable to surface-adsorbed phytochemicals. Antifungal testing against Aspergillus flavus using the poisoned food technique revealed substantial growth inhibition, reaching 58.48 percent at one hundred micrograms per milliliter, 64.55 percent at five hundred micrograms per milliliter, and 75.35 percent at one thousand micrograms per milliliter. Antihemolytic tests on human erythrocytes showed negative inhibition values of negative 15.79 percent and negative 3.29 percent at twenty and forty micrograms per milliliter, transitioning to 12.50 percent protection at one hundred micrograms per milliliter.
To identify safe exposure limits and assess potential phytotoxicity, the research team conducted a radish seed bioassay across nanoparticle concentrations spanning zero to thirty micrograms per milliliter. Results demonstrated a clear biphasic response: moderate concentrations promoted early seedling development, whereas higher levels caused marked growth suppression. Radish germination after twenty-four hours increased from 36.67 percent in water controls to 76.67 percent at fifteen micrograms per milliliter, while forty-eight-hour germination rose from 63.33 percent to 86.67 percent. Seedling length similarly peaked at fifteen micrograms per milliliter, measuring 38.67 millimeters compared to 10.33 millimeters in untreated controls. However, seedling length dropped sharply to 6.00 millimeters at twenty micrograms per milliliter and further declined to 3.67 millimeters at thirty micrograms per milliliter. This bioassay demonstrated that biological stimulation was restricted to lower concentrations, justifying the selection of five, ten, and fifteen parts per million for field testing on wheat crops.
The field trial was carried out during the 2025–2026 growing season on loam soil with a pH of 7.99, electrical conductivity of 0.72 decisiemens per meter, and 0.98 percent organic matter. Four wheat cultivars—Borlaug-16, Zincol-16, NARC-SUPER, and Wafaq-23—were grown in three-by-three-meter plots. Foliar treatments of distilled water or nanoparticles at five, ten, and fifteen parts per million were sprayed at tillering, booting, and heading stages. Factorial ANOVA revealed that cultivar, treatment, and their interaction significantly influenced plant height, spike length, grains per spike, biological yield, grain yield per plant, and thousand-kernel weight. Beyond the 194.89 percent grain yield increase in Borlaug-16, Wafaq-23 exhibited an 8.09 percent increase in plant height and a 26.35 percent increase in spike length. Pairwise correlations identified strong positive associations between plant height and spike length, as well as between spike length and biological yield, confirming coordinated agronomic gains across the field plots.
Foliar application of green silver nanoparticles stimulated photosynthetic pigment accumulation and nitrogen metabolism across all four wheat cultivars. Factorial analysis indicated significant main and interaction effects on chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids, with the fifteen parts per million dosage yielding the largest responses. Zincol-16 exhibited the greatest increases in chlorophyll a and total chlorophyll, rising by 216.24 percent and 204.88 percent over untreated controls, respectively. Chlorophyll b increased most in NARC-SUPER by 217.94 percent, while carotenoids rose by 274.27 percent in Wafaq-23. Concurrently, nitrogen metabolism traits showed marked improvements, with urease activity rising by 169.25 percent in Zincol-16. Leaf ammonia increased by 131.87 percent in NARC-SUPER, and nitrate content climbed by 24.35 percent in NARC-SUPER and 20.99 percent in Zincol-16. Correlation analysis revealed positive relationships among nitrogen traits and photosynthetic pigments, indicating coordinated physiological enhancement, although direct metabolic fluxes were not quantified.
The physiological responses were accompanied by strengthened antioxidant enzyme activities and reduced oxidative stress markers. Factorial ANOVA indicated that nanoparticle concentrations significantly enhanced superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, and ascorbate oxidase activities. Catalase activity increased by up to 65.38 percent in Zincol-16, while ascorbate peroxidase rose by 46.15 percent in Borlaug-16. Concurrently, levels of oxidative stress biomarkers declined substantially under fifteen parts per million treatments: malondialdehyde decreased by 50.00 percent in both NARC-SUPER and Wafaq-23, hydrogen peroxide declined by 33.04 percent in Borlaug-16, and proline dropped by 50.66 percent in Zincol-16. Electrolyte leakage decreased by 26.63 percent in Wafaq-23, reflecting improved cell membrane stability, while relative water content rose by 22.20 percent in Borlaug-16. Correlation modeling revealed strong negative associations between antioxidant enzyme levels and oxidative stress biomarkers, indicating that nanoparticle applications were associated with enhanced membrane preservation and improved cellular water status.
Mature grain profiling, stem ionomics, and multivariate analyses further clarified the physiological responses and study limitations. Grain protein content increased by 63.13 percent and total sugars rose by 291.53 percent in Borlaug-16, while starch content increased by 106.82 percent in Wafaq-23 under fifteen parts per million treatments. Stem ionomics showed that phosphorus, sulfur, manganese, potassium, and calcium increased substantially in Wafaq-23, while zinc consistently declined across all cultivars by 4.4 to 38.1 percent. Principal component analysis accounted for 70.2 percent of total variation, separating nanoparticle treatments from controls along the first axis. Crucially, the authors emphasized experimental limitations: the control consisted of distilled water rather than Aloe vera extract or silver nitrate solutions, meaning responses cannot be attributed solely to metallic silver nanoparticles. Additionally, measurements relied on three within-plot subsample plants rather than independent field-plot replicates, and physiological mechanisms were inferred without direct gas-exchange or carbon-flux measurements.
Subject of Research: Foliar application of green-synthesized silver nanoparticles on bread wheat
Article Title: Aloe vera-mediated green-synthesized silver nanoparticles enhance physiological performance and yield in bread wheat
Article References: Tabassum, A., Akhtar, S., Elahi, M., Younas, M., Naeem, K., & Quraishi, U. M. (2026). Aloe vera-mediated green-synthesized silver nanoparticles enhance physiological performance and yield in bread wheat. Discover Plants, 3(1), Article 538. https://doi.org/10.1007/s44372-026-01008-x
Image Credits: AI Generated
DOI: 10.1007/s44372-026-01008-x
Keywords: Triticum aestivum, green synthesis, silver nanoparticles, Aloe vera extract, foliar application, bread wheat cultivars, Borlaug-16, Wafaq-23, Zincol-16, grain yield, antioxidant enzymes, photosynthetic pigments, nitrogen metabolism, stem ionomics, malondialdehyde, Aspergillus flavus, phytotoxicity assay, dynamic light scattering
Tags: Aloe vera extractantioxidant enzymesAspergillus flavusBorlaug-16bread wheat cultivarsdynamic light scatteringfoliar applicationgrain yieldgreen synthesismalondialdehydenitrogen metabolismphotosynthetic pigmentsphytotoxicity assaysilver nanoparticlesstem ionomicsTriticum aestivumWafaq-23Zincol-16
