Nanoscale magnesium oxide reduces the accumulation and toxicity of micro/nanoplastics by accelerating root lignification and alleviating endoplasmic reticulum stress.

The risk to agricultural production and human health from micro/nanoplastics (MNPs) exposure cannot be ignored, making it imperative to find effective mitigation strategies. Nanoscale magnesium oxide (MgO·NP) has been widely demonstrated to enhance plant stress resistance by activating defense pathways. However, its ability to mitigate MNPs stress remains unexplored. A greenhouse soil culture experiment was conducted by co-adding five predominant soil MNPs (polyethylene terephthalate (PET), polyethylene (PE), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC)) at 1 g·kg⁻¹ each. After 30 days, pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) analysis of tomato leaves revealed a distinct absorption profile for MNPs: PET > PE > PS > PP > PVC. Soil amendment with 40 mg·kg⁻¹ MgO·NP significantly inhibited MNPs accumulation in tomatoes, reducing PET, PS, and PVC by 57.44%, 76.14%, and 31.82%, respectively. Multi-omics analyses revealed that MgO·NP upregulates phenylpropanoid biosynthesis genes (PAL, 4CL, CCR). This upregulation elevated lignin content by 26.7% and stimulated root lignification, a response that may be linked to the observed reduction in apoplastic uptake and transport of MNPs. Furthermore, MgO·NP was associated with changes in ERAD‑related gene expression and may have contributed to mitigating protein misfolding and organelle stress under MNPs exposure. In conclusion, this study demonstrates that exogenous application of 40 mg·kg⁻¹ MgO·NP significantly inhibits the accumulation and mitigates the toxicity of MNPs in tomato plants. These findings may offer a feasible strategy for alleviating the adverse impacts of MNPs contamination on agricultural production.