Study of the effect of pre-sowing treatment of wheat seeds with manganese dioxide nanoparticles on salt stress

Relevance. Soil salinity is a global stressor limiting wheat productivity. Manganese participates in photosynthesis and antioxidant defense, but the efficacy of its nanoforms for improving salt tolerance remains underexplored. This study aimed to evaluate the effect of pre-sowing seed treatment with MnO₂ nanoparticles on wheat seedlings under salt stress.

Methods. MnO₂ nanoparticles were synthesized using alkyl dimethyl amine oxide as a stabilizer. Phase composition was assessed using X-ray diffraction analysis. The energetics of interactions were estimated using quantum chemical modeling (B3LYP/6-31G*). Wheat seeds were treated with a MnO₂ suspension (1 mg/L) and germinated at 0.5–5.0% NaCl. Morphometric parameters and photosynthetic pigment content were determined (spectrophotometry). Data were analyzed using a two-way ANOVA (p < 0.05).

Results. X-ray diffraction analysis revealed the presence of an amorphous manganese dioxide phase with a hexagonal lattice. Modeling confirmed the energetic favorability of MnO₂ binding to the N-oxide group of the stabilizer (ΔE = 1299 kcal/mol). In the control, increasing NaCl to 1.0% reduced the total pigment content from 0.087 to 0.032 mg/g, while 2.5% NaCl caused seedling mortality. MnO₂ treatment ensured survival at 2.5% NaCl (total pigment content 0.074 mg/g), which is only slightly inferior to the control at 0.5% NaCl. At 1.0% NaCl, the pigment content in the test samples (0.078 mg/g) was comparable to the control at 0.5% NaCl, indicating complete stress relief. An increase in the proportion of carotenoids indicates activation of antioxidant defenses. MnO₂ nanoparticles effectively protect the photosynthetic apparatus of wheat under salt stress, opening up prospects for the development of new forms of fertilizer.

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