“…181,[186][187][188] In general, compared with the aboveground parts of plants, the oxidative damage of roots exposed to MNPs is more significant because of the direct contact between roots and MNPs, which is characterized by a significant increase in H 2 O 2 and conjugated dienes. 189 In a hydroponic experiment, it was found that the content of malondialdehyde (MDA) increased as the concentration of Al 2 O 3 and CuO NPs increased, and reached the highest at 2000 mg L −1 , which was 25.8 ± 2.3 and 40.8 ± 3 (nM × 10 2 ) per g FW, respectively. The subsequent DCF fluorescence labeling results showed that higher concentrations of Al 2 O 3 and CuO NPs (200 and 2000 mg L −1 ) induced a sharp increase in DCF fluorescence in roots, indicating the formation of ROS in roots.…”