Manganese is essential to plants in tiny amounts, but manganese nanoparticles applied to wheat leaves increased cellular manganese twenty to forty-five times and activated a clear stress response without obvious leaf chlorosis or necrosis. Manganese in micro amounts is necessary for proper growth and development of plants, but both deficiency and excess distort physiological processes in plant cells.

The paper also points to increasing soil contamination with manganese compounds, with over-fertilization and climate change identified as potential contributors. Drought and hot summers favor soil acidification and increasing manganese two, the form most easily absorbed by plant roots, while manganese is transported from roots to aerial parts and accumulated in leaves.

Excessive accumulation of manganese in chloroplasts distorts their structure and disrupts cell performance through oxidative stress. The experiments focused on two wheat cultivars and the incorporation of manganese oxide nanoparticles into their cells after foliar application.

This form of manganese nanoparticle treatment was rarely described, and the study aimed to provide information about direct action by nanoparticles accumulated through the leaf surface. The need to study penetration through leaves was linked to increasing airborne manganese nanoparticles from dust emissions, mainly during steel production, iron production, and coal combustion.

The experiments checked manganese accumulation, oxidative stress after leaf penetration, changes in membrane lipids, and changes in chloroplast physicochemical properties. The study used spring wheat cultivars Alibi and Nimfa. The grains were sterilized with eighty percent ethanol and eighty percent perhydrol, rinsed four times with distilled water, and germinated at twenty degrees Celsius in the dark.

The seedlings were grown in fifty percent Hoagland nutrient solution under forty-five to fifty percent relative humidity, eight hundred micromoles of photons per square meter per second, and a sixteen-hour photoperiod for ten days. Manganese nanoparticles were applied to two fully developed leaves at one hundred twenty-five and two hundred fifty milligrams per milliliter, with one milliliter per plant; control leaves received pure water.

After five days, the seedlings were harvested, aerial parts were selected, and tissues were washed, weighed, and frozen in liquid nitrogen. Electrolyte leakage and electrokinetic potential were determined in fresh leaves.

For the membrane model, lipid monolayers were formed by applying chloroform solutions of appropriate lipids to aqueous surfaces. Surface pressure isotherms were recorded with a Langmuir trough equipped with a platinum-Wilhelm plate for surface-tension detection, with an accuracy of plus or minus zero point one millinewton per meter.

The experiments were carried out at twenty-five degrees Celsius, and measurements were repeated three or four times with repeatability of zero point one to zero point three square angstroms. The data were presented as means plus or minus standard error. Statistical analysis used Duncan’s multiple-range test, with significance estimated at p less than zero point zero five using PC SAS eight point zero software.

Significance of the means was evaluated with SAS analysis of variance. During the five days after manganese nanoparticle application, observation of the leaf surface showed no drastic visual changes, including chlorosis or necrosis. Even so, both treatments reduced leaf fresh weight.

Table one compares Alibi and Nimfa wheat leaves under control conditions and after one hundred twenty-five or two hundred fifty MnNPs, measuring fresh weight, manganese content, electrolyte leakage, MDA, and antioxidant enzymes. Letter annotations mark statistically significant differences within each cultivar at p less than or equal to 0.05.

Under control conditions, superoxide dismutase activity was higher in Alibi by approximately three point five percent. After one hundred twenty-five nanoparticles, superoxide dismutase increased significantly, with the increase greater for Alibi by about ten percent.

The two hundred fifty milligrams per milliliter dose only slightly elevated enzyme activity, by about five percent, compared with the lower nanoparticle dose in Nimfa, while Alibi showed a continuous thirteen percent enhancement. Catalase and peroxidase were less active in control Alibi plants than in Nimfa plants.

Catalase increased more at the lower dose in Nimfa, by about sixteen percent, and at the higher dose in Alibi, by over twice. Peroxidase showed the reverse dependence, with particularly strong activity, approximately ninety percent, in Nimfa at the higher nanoparticle dose.

Malondialdehyde concentration was ten percent lower in control Nimfa than in control Alibi and increased after manganese nanoparticle administration. In Alibi, the similar fifteen percent rise appeared at one hundred twenty-five nanoparticles, while in Nimfa it appeared at the higher dose.

In Alibi, starch content increased with the applied manganese nanoparticle dose by forty-four and seventy-seven percent, respectively. Nimfa showed a similar, approximately thirty percent rise in starch content after exposure to one hundred twenty-five and two hundred fifty nanoparticles.

Chlorophyll a decreased as nanoparticle dose increased in both cultivars: by five and four percent at one hundred twenty-five nanoparticles, and by fifteen and twelve percent at two hundred fifty nanoparticles for Alibi and Nimfa, respectively. Chlorophyll b showed the reverse dependence.

Figure 1 compares starch and chlorophyll in leaves of the Alibi and Nimfa cultivars under control conditions and after treatment with one hundred twenty-five or two hundred fifty manganese nanoparticles. Starch increases with nanoparticle dose in Alibi, while Nimfa shows an approximately thirty percent rise at both doses; chlorophyll a declines as dose increases in both cultivars, whereas chlorophyll b shows the reverse pattern.

These responses matter because they indicate dose- and cultivar-dependent changes in leaf carbohydrate storage and photosynthetic pigments. Spectrometric studies showed that manganese levels in leaves increased by about twenty to forty-five times relative to control, suggesting penetration of nanoparticles into internal leaf structures.

At the highest nanoparticle dose, greater manganese content was noted for Alibi, even though manganese ions delivered through the root system previously resulted in lower absorption by Alibi than by Nimfa. The possibility that nanoparticles enter cells through the same transporters as other ions has been suggested, while knowledge of manganese ion transporters remains limited.

The properties of manganese transporters in the plasma membrane of leaf cells have not been clearly described, although their presence in leaf organelles has been suggested. Figure 2A shows that manganese nanoparticles altered chloroplast membrane electrokinetic potential in both cultivars, with the strongest shift appearing after the one-hundred-twenty-five treatment.

Panel B separates total leaf lipids into phospholipids, MGDG, and DGDG, showing that increasing nanoparticle concentration was accompanied by changes in all three fractions, particularly a redistribution from phospholipids toward galactolipids. The authors use the letter groupings to mark statistically significant treatment differences, linking membrane-surface changes with lipid remodeling.

Table two compares limiting molecular area, collapse pressure, and compression modulus for DGDG, MGDG, and phospholipid monolayers from Alibi and Nimfa leaves, before and after one hundred twenty-five or two hundred fifty manganese nanoparticles. The authors report treatment-associated shifts in these membrane-surface parameters, with statistical differences marked by lowercase letters for Alibi and capital letters for Nimfa.

This matters because the measurements indicate how manganese nanoparticle exposure altered the structural and mechanical behavior of membrane lipid layers, alongside the reported reduction in seedling fresh weight. Manganese nanoparticles penetrated the leaves, increasing the cellular manganese pool, and manganese uptake through leaves differed from uptake through the root system.

The investigated concentrations initiated stress reactions, including generation of excessive reactive oxygen species, manifested in activation of antioxidant enzymes. Differences between cultivars in catalase and peroxidase activation may indicate different sensitivity to manganese nanoparticle stress.

Treatment led to photosynthetic disorders, increased starch concentration, and lowered chlorophyll synthesis. The increased electrokinetic potential of chloroplast membranes indicated changes in their polar parts, while rebuilding of hydrophobic parts in the direction of fatty acid saturation could reduce manganese incorporation into chloroplasts.

Greater changes in Alibi could be associated with greater manganese penetration into the cells of this cultivar. The main takeaway is that foliar manganese nanoparticles penetrated wheat leaves and disturbed photosynthesis, antioxidant balance, and membrane properties, with stronger changes associated with greater manganese penetration in Alibi.