Magnesium Oxide Nanoparticles Ease Lead Stress in Radish Seedlings

Radish seedlings soaked in a solution of magnesium oxide nanoparticles before being exposed to lead nitrate grew markedly better than seedlings facing the same lead doses without the nanoparticle treatment, according to a laboratory study conducted at DAV University in Jalandhar, Punjab, India. The researchers, Ayushi Gautam, Vineet Kumar, and Praveen Guleria, report that nanopriming with 150 micrograms per milliliter of biologically synthesized magnesium oxide nanoparticles rescued the growth of lead-stressed seedlings while simultaneously altering their photosynthetic pigments and boosting their antioxidant defenses. The work, published in the journal Bioscience Nanotechnology, adds to a small but growing body of evidence that metal oxide nanoparticles can help crop plants cope with heavy metal contamination in soil.

The experimental setup was straightforward. Radish seeds were divided into groups and exposed to lead nitrate at three concentrations: 0.075 millimolar, 0.15 millimolar, and 0.3 millimolar, designated L1, L2, and L3 respectively. A parallel set of seeds was first incubated with the magnesium oxide nanoparticles for 16 hours before receiving the same lead treatments. All seeds germinated in petri plates kept at 25 degrees Celsius under a 16-hour light photoperiod, and the seven-day-old seedlings were then measured for a battery of morphological and biochemical traits. The study followed a completely randomized factorial design with three biological replicates for each treatment, and differences between group means were assessed with one-way analysis of variance followed by Duncan’s multiple range test at a significance threshold of P < 0.05.

Lead alone proved damaging across the board. Shoot length fell by 24 percent at the lowest lead dose, 38 percent at the middle dose, and 56 percent at the highest dose compared with untreated controls. Root length, often the most sensitive organ to soil metal toxicity, dropped by 13, 31, and 69 percent at the same three doses. Fresh biomass accumulation declined even more steeply, by 38, 50, and 69 percent.

When the nanoprimed seeds faced the same lead doses, the picture changed considerably. Shoot length in the nanoprimed, lead-treated groups exceeded that of the corresponding lead-only groups by 17, 18, and 43 percent at L1, L2, and L3 respectively. Root length showed even more dramatic recovery, rising by 49, 13, and 91 percent relative to the lead-only counterparts. Fresh biomass, the most economically relevant trait for a root vegetable, increased by 53, 25, and 73 percent in the nanoprimed lead-stressed plants compared with their lead-only counterparts. The authors interpret these gains as evidence that a brief pre-sowing exposure to the nanoparticles primed the seedlings’ physiology in a way that buffered them against the metal’s toxic effects during germination and early growth.

The nanoparticles themselves were synthesized using clove extract, a plant-mediated approach the authors describe as environmentally benign compared with physical or chemical synthesis routes. The authors note that plant-mediated synthesis is generally considered less toxic than conventional methods, which can leave behind waste residues and reaction by-products that contaminate the final product.

Photosynthetic pigments told a more nuanced story. Lead exposure reduced total chlorophyll by 5, 23, and 36 percent at the three doses, with chlorophyll a falling by up to 28 percent and chlorophyll b by as much as 56 percent. Carotenoid content dropped by 8, 42, and 45 percent. Surprisingly, nanopriming did not restore these pigments; instead, it further reduced them. Chlorophyll a fell an additional 10, 4, and 6 percent in the nanoprimed lead-stressed groups relative to their lead-only counterparts, chlorophyll b dropped another 5 to 8 percent, and total chlorophyll declined by a further 4 to 8 percent. Carotenoids followed the same pattern, decreasing by an additional 5 to 19 percent.

The antioxidant machinery showed clearer signs of nanoparticle-mediated support. Lead stress alone reduced flavonoid content by 18, 31, and 52 percent and total phenolics by 1, 4, and 7 percent across the three doses, while also depressing the free radical scavenging capacity measured by the DPPH assay. Nanopriming reversed these trends: phenolics rose by 2 to 5 percent and flavonoids by 20 to 33 percent in the nanoprimed lead-stressed groups compared with their lead-only counterparts. Among the antioxidant enzymes, superoxide dismutase activity increased by 4, 14, and 22 percent, ascorbate peroxidase by 57, 39, and 16 percent, and catalase by 13, 17, and 29 percent in the nanoprimed groups relative to the corresponding lead-only groups.

Oxidative stress markers confirmed the protective effect. Malondialdehyde, a breakdown product of lipid peroxidation that serves as a proxy for membrane damage, rose by 28, 31, and 43 percent in the lead-only groups compared with controls. Hydrogen peroxide, a reactive oxygen species, climbed by 20, 28, and 43 percent at the same doses. Nanopriming brought both markers down: malondialdehyde fell by 17, 15, and 8 percent, and hydrogen peroxide by 17, 14, and 13 percent in the nanoprimed lead-stressed groups relative to their lead-only counterparts. The authors suggest that the coordinated reduction in oxidative stress markers, combined with the elevated antioxidant enzyme activities and phenolic compounds, explains how the nanoprimed seedlings maintained better growth despite ongoing lead exposure.

Not every measured parameter moved in a direction that would be considered favorable in an agricultural context. Carbohydrate content, which fell by 2, 5, and 7 percent under lead stress alone, dropped a further 1 to 4 percent with nanopriming. Protein content, reduced by 8, 12, and 21 percent by lead alone, fell another 5 to 11 percent in the nanoprimed groups. In vitro protein digestibility declined by 13, 14, and 19 percent with nanopriming relative to the lead-only groups, and protein solubility also decreased.

The study’s scope is limited to seven-day-old seedlings grown in controlled petri plate conditions rather than mature plants in lead-contaminated field soil, and the lead concentrations used, while spanning a range that produced measurable toxicity, were applied through filter papers in a growth chamber rather than through a realistic soil matrix. The authors also note that very few prior studies have examined magnesium oxide nanoparticles specifically for heavy metal stress mitigation in crops, with most nanoparticle priming work on lead stress having focused on iron oxide, silicon dioxide, or calcium oxide particles. They had previously reported that the same clove-derived magnesium oxide nanoparticles alleviated salt stress in radish, and the present results extend that finding to a different abiotic stressor. Whether the growth rescue and antioxidant enhancement observed here would translate to yield gains in lead-contaminated agricultural fields, and whether the nanoparticle treatment itself poses any accumulation risk in the edible root, remain questions the current data cannot answer.

Subject of Research: Effects of biologically synthesized magnesium oxide nanoparticles on lead stress tolerance in radish seedlings

Article Title: Enhanced antioxidant potential and regulated photosynthetic machinery on MgO-NPs exposure induced heavy metal lead stress tolerance in radish

Article References: Gautam, A., Kumar, V., & Guleria, P. (2026). Enhanced antioxidant potential and regulated photosynthetic machinery on MgO-NPs exposure induced heavy metal lead stress tolerance in radish. Bioscience Nanotechnology, 2(1), Article 9. https://doi.org/10.1186/s44331-026-00016-8

Image Credits: AI Generated

DOI: 10.1186/s44331-026-00016-8

Keywords: magnesium oxide nanoparticles, lead stress, radish, nanopriming, antioxidant defense, oxidative stress, chlorophyll, seed germination, heavy metal toxicity, plant biotechnology, clove extract, abiotic stress