Sunflower-Grown Zinc Nanoparticles Boost Eggplant Growth and Nutrition, Study Finds

A team of Nigerian researchers has shown that tiny zinc oxide particles made from sunflower leaves can dramatically reshape how eggplants grow, cope with oxidative stress, and pack away nutrients. In a greenhouse study conducted at Lagos State University, foliar sprays of the plant-derived nanoparticles produced taller plants, more leaves, larger leaf areas, and richer mineral and protein profiles than untreated controls. The work, published in BMC Agriculture, adds to a growing body of evidence that green-synthesized nanomaterials could serve as next-generation fertilizers at a time when conventional synthetic inputs are increasingly criticized for slow mineralization, soil degradation, and nutrient leaching.

The researchers began with sunflower leaf extract, chosen because sunflowers are rich in flavonoids and phenolic acids, phytochemicals that act as natural reducing and stabilizing agents for zinc ions. Twenty-five grams of air-dried, milled sunflower leaves were stirred into 500 milliliters of distilled water at 50 degrees Celsius for three hours to produce the extract. Zinc oxide solution was then added, acidified with hydrochloric acid, and heated to 80 degrees Celsius to encourage particle formation. Sodium hydroxide was added dropwise until the pH reached between 10 and 11, darkening the mixture and driving the nanoparticles to precipitate. After centrifugation, washing, and drying at 105 degrees Celsius, the team had a batch of biologically derived zinc oxide nanoparticles ready for rigorous characterization.

Fourier transform infrared spectroscopy revealed that the nanoparticles carried hydroxyl groups, amides, and carbon-hydrogen bonds as their major functional groups, fingerprints largely absent from the original leaf extract. The researchers interpreted these signatures as evidence that the zinc oxide had successfully complexed with biomolecules from the sunflower leaves. Scanning electron microscopy showed a smooth surface on the nanoparticles, in contrast to the rough texture of the raw extract, a difference the authors linked to enhanced adhesion, catalytic activity, and interaction with surrounding soil and plant molecules. Transmission electron microscopy revealed homogeneous, rod-shaped particles with an average diameter of just 4.19 nanometers, a size the team says likely boosts solubility and diffusion rates, key mechanisms for nutrient absorption in plant tissue.

X-ray diffraction confirmed a crystalline structure, with the highest diffraction intensity recorded in the nanoparticles between zero and 20 degrees. Energy-dispersive spectroscopy then quantified the elemental makeup: zinc dominated the nanoparticles at 50.24 percent, while silica was the major element in the leaf extract at roughly 70 percent. The authors argue that the high surface area, pure crystalline nature, and rod-like morphology of the particles give them the surface energy needed to propel physiological activities such as nutrient uptake, and that the presence of zinc itself likely enhanced the morphological, physiological, and biochemical changes observed in the treated eggplants.

To test the particles in living plants, the team grew eggplant seedlings in sandy-loam soil in the greenhouse and sprayed them with four concentrations of the nanoparticles, 25, 50, 75, and 100 percent, once every two weeks for eight weeks, alongside a control group watered with distilled water. The experiment followed a completely randomized design with five replications. The strongest concentration produced the most striking results: plants sprayed with 100 percent nanoparticles reached an average height of 19.93 centimeters and carried 34.75 leaves, with a leaf area of 86.77 square centimeters, a specific leaf area of 50.96 square meters per kilogram, and a leaf area index of 0.30 square meters per square meter. Relative growth rate peaked at 0.31 grams per square meter per day, while net assimilation rate and leaf area ratio were highest at the 75 percent concentration.

The biochemical story was equally revealing. Reactive oxygen species, the damaging molecules that plants generate under stress, were significantly downregulated in nanoparticle-treated plants. Malondialdehyde, a marker of lipid peroxidation, peaked at 23.23 micromoles per gram of fresh weight in control leaves, while hydrogen peroxide reached 41.82 nanomoles per gram of dry weight in control leaves and 26.98 nanomoles per gram in control roots. In contrast, the lowest values of these stress markers appeared in the leaves and roots of plants sprayed with the full-strength nanoparticle solution, suggesting the particles had ameliorated oxidative damage rather than provoking it.

Antioxidant enzyme activity told a complementary story. Superoxide dismutase, ascorbate peroxidase, catalase, glutathione reductase, and glutathione S-transferases were all substantially upregulated in the leaves of control plants, which the researchers interpret as a defensive response to the reactive oxygen species accumulating in untreated tissue. Once the nanoparticles suppressed those reactive species, the antioxidant machinery no longer needed to run at full tilt, and enzyme activities dropped to their lowest levels in the 100 percent treatment group. The authors note that zinc is known to bind amino acids, restrict reactive oxygen accumulation, improve antioxidant activity, and maintain osmotic balance, mechanisms that may underpin the stress-buffering effect they observed.

Nutritional analysis added a final layer of significance. Moisture, dry matter, and fat content were highest in control plants, but ash, crude fiber, crude protein, and carbohydrate all increased significantly in plants sprayed with 100 percent nanoparticles, with crude protein reaching 2.45 percent and carbohydrate 3.20 percent. Mineral profiles shifted as well: sodium, potassium, and calcium peaked in the 100 percent treatment, while magnesium at 58.80 milligrams per 100 grams and phosphorus at 90.86 milligrams per 100 grams were significantly higher in plants treated with the 75 percent concentration. The team attributes these gains to the formation of new leaves and biomass, and to the nanoparticles’ ability to distribute nutrients effectively through plant tissue, linking nutritional status to photosynthetic potential.

The implications reach well beyond one vegetable. Eggplant, a Solanaceae crop consumed widely across Africa for food and indigenous purposes, often suffers from the continuous application of synthetic fertilizers, which mineralize slowly due to low surface area and contribute to leaching, erosion, and soil degradation. Ultrafine, plant-derived particles could offer a sustainable alternative, rejuvenating depleted soils and regulating metabolic processes in crops. The authors conclude that zinc oxide nanoparticles at 100 and 75 percent concentrations should be considered as flora-based fertilizers to improve eggplant growth and buffer the plants against erratic climatic conditions.

Still, the researchers are careful to flag what their study did not do. They did not optimize concentrations of the sunflower leaf extract itself, assess its potential as a biofertilizer, or evaluate toxicity, and they recommend that future work investigate the single and synergistic effects of zinc oxide nanoparticles and sunflower leaf extract, along with their potential toxicological risks. That caution matters: reviews of zinc oxide nanoparticles in plant science have emphasized the need to understand ecological risks and dose-dependent effects before widespread deployment. For now, the Lagos State University team’s rod-shaped, 4-nanometer particles stand as a compelling proof of concept that a common garden flower can help manufacture a fertilizer capable of growing taller, greener, and more nutritious eggplants.

Subject of Research: Green-synthesized zinc oxide nanoparticles as foliar nanofertilizers modulating growth, oxidative stress, and nutrition in eggplant

Article Title: Characterization and modulatory influence of flora-based zinc oxide nanoparticles on morpho-physiological and biochemical changes in eggplant

Article References: Ojewumi, A. W., Osifeko, O. L., Fawibe, O. O., Shotonwa, I. O., Sheily, N. E., Akinyemi, O. F., Omolokun, K. T., Oyelami, B. A., Adelugba, D. O., & Ojekale, A. B. (2026). Characterization and modulatory influence of flora-based zinc oxide nanoparticles on morpho-physiological and biochemical changes in eggplant. BMC Agriculture, 2(1), Article 6. https://doi.org/10.1186/s44399-025-00028-4

Image Credits: AI Generated

DOI: 10.1186/s44399-025-00028-4

Keywords: zinc oxide nanoparticles, eggplant, sunflower leaf extract, green synthesis, nanofertilizer, foliar application, reactive oxygen species, antioxidant enzymes, plant nutrition, sustainable agriculture, Lagos State University, BMC Agriculture