Table 7 Phytotoxicity of nanoparticles based on iron oxides

Helianthus annuus

γ-Fe₂O₃ 20–100 nm

50, 100 mg L⁻¹

Effect on the root functionality was investigated

The treatment with 50 mg L⁻¹ FeNPs significantly reduced the root hydraulic conductivity (Lo) by up to 26% at 100 mg L⁻¹ FeNPs, but it had no effect on plant biomass production, on shoot or root elongation, and it did not induce oxidative stress in the plant

[106]

Solanum lycopersicum

nZVI < 50 nm

γ-Fe₂O₃ 20–100 nm

50, 100 mg L⁻¹

Effect on the root functionality was investigated

The treatment with 100 mg L⁻¹ of Fe₂O₃ NPs inhibited 40% of the root hydraulic conductivity (Lo), with nZVI no effect on Lo was observed

[73]

Lactuca sativa

FeOx NPs <50 nm

1, 5, 10, 20, 50 mg L⁻¹

A 5-day seed germination test was used to test how different FeOx NPs affected the plant growth in comparison with their respective ionic or solid counterparts

FeOx NPs significantly enhanced root elongation of lettuce seedlings by 12%–26%, indicating that FeOx NPs could be used as an Fe fertilizer as well at low application rates (5–20 mg L⁻¹). At a concentration of 50 mg L⁻¹, FeOx NPs decreased root elongation of lettuce seedlings by 20%

[83]

Oryza sativa

γ-Fe₂O₃ 7–13 nm

2, 20, 200 mg L⁻¹

A 7-day seed germination test was used

Root phytohormone inhibition abscisic acid (ABA) and indole-3-acetic acid (IAA) was positively correlated with Fe₂O₃ NPs concentrations, indicating that Fe₂O₃ had a significant influence on the production of these hormones

[107]