Phytotoxicity and growth enhancement properties of magnesium and zinc co-doped aluminum oxide nanoparticles on barley (Hordeum vulgare L.)

Abstract

Nanotechnology has been utilized in diverse domains, encompassing sustainable agriculture. However, the ecotoxicity and environmental safety of nanoparticles need to be evaluated before their large-scale use. This study synthesizes and characterizes magnesium (Mg) and zinc (Zn) co-doped aluminum (Al) oxide (MgZnAl₂O₄) NPs and elucidates its potential growth-promoting or genotoxic performance on barley (Hordeum vulgare L.). XRD, EDX, TEM, SEM, and XPS were used to characterize the MgZnAl₂O₄ NPs. After characterization, the seedlings were grown in a hydroponic solution containing 0, 50, 100, 200, and 400 mg L⁻¹ NPs for 3 weeks. The germination, growth indices, photosynthetic parameters, and nutrient absorption properties were determined. Confocal microscopy, TEM, and SEM were utilized to follow the path and reveal the structural and morphological effects of NPs. The potential genotoxic effect was evaluated using the RAPD-PCR method. Elemental composition analysis of plant parts confirmed that synthesized MgZnAl₂O₄ NPs, sized at 21.8 nm, were up-taken by the plant roots, leading to increased Mg, Zn, and Al contents of leaves. In addition, compared with the untreated control, the abundance of Ca, K, B, Fe, Mn, and Cu were increased by the NPs treatment. In addition, physiological indices like germination rate (~ 11%), root and leaf growth (15–29%), chlorophyll, and carotenoids (~ 39%) pigments were significantly raised by the NPs inclusion. It can be concluded that low concentrations (< 200 mg L⁻¹) of MgZnAl₂O₄ NPs enhance growth parameters effectively and are safe for plant growth. On the other hand, a phytotoxic and genotoxic impact was observed at high concentrations (100–400 mg L⁻¹). However, considerable amounts of NPs were found to be adsorbed on roots, disrupting root morphology and cell membrane integrity, thus nutrient trafficking and transport. Therefore, it is recommended that MgZnAl₂O₄ NPs can be used in barley breeding programs at low concentrations. Adding micro- or macroelements required by plants to the NP composition is a promising way to compensate for plant nutrition. However, the negative effects of MgZnAl₂O₄ NPs on the environment and other living beings due to their genotoxic effects at high doses must be carefully considered.