Hematite nanoparticles influence ultrastructure, antioxidant defenses, gene expression, and alleviate cadmium toxicity in <i>Zea mays</i>
Ola A. Youssef, Amel Tammam, Ranya El-Bakatoushi, Asmaa Mohamed Alframawy, Mahmoud Mohamed Emara, Laila M. El-Sadek
Abstract
The present study describes the response of Zea mays to hematite nanoparticles (NPs) using five concentrations ranged from 500 to 8000 mg kg−1, and Cd2+ concentrations (110 or 130 mg kg−1 Cd2+) only or combined with 500 mg kg−1 NPs, using soil culture. The endpoints measured were root/shoot growth, elements uptake, ultra-structural alterations, lipid peroxidation, some antioxidant enzyme activities, and their relative gene expressions. The results indicated that hematite NPs exhibited a dual behavior, in which 500 mg kg−1 NPs significantly enhanced maize growth, while 4000 and 8000 mg kg−1 NPs significantly increased lipid peroxidation and superoxide dismutase (SOD) activity displaying positive correlation with SOD expression in shoots (r = +0.472, p < .05). Ultrastructure micrographs revealed the appearance of aggregated NPs inside the vacuoles. The stunted growth, perturbed ultra-structure, and high lipid peroxidation were used as toxicity biomarkers for Cd2+. However, combined treatments of 500 mg kg−1 NPs and Cd2+ significantly stimulated growth and glutathione reductase activity, while significantly reduced catalase (CAT) activity displaying positive correlation with CAT expression in roots (r = +0.694, p < .01). In conclusion, hematite NPs could alleviate Cd2+ toxicity not at the level of antioxidant defense, but by affecting mechanisms of Cd2+ detoxification.