Fig. 6. Production of ROS after exposure to 0 (A), 200 (B), 400 (C) and 600 mg L^–1 (D) GO suspensions was measured using the fluorescence stereomicroscope. (E) Production of ROS after exposure to 0–600 mg L^–1 GO suspensions was measured using the microplate reader. Values are presented as the mean ± SD. Values that are significantly different from the control are indicated by asterisks (one-way ANOVA, *p < 0.05, **p < 0.01).