Effect of Graphene Oxide on Growth of Wheat Seedlings: Insights from Oxidative Stress and Physiological Flux

In this study, the responses of wheat seedlings to graphene oxide (GO) were investigated at a wide concentration range of 0–1000 mg L−1, including oxidative stress, real-time membrane potential as well as proton and calcium ion fluxes. The results show that GO induced a hormesis effect on root growth (low concentration (100 mg L−1) promotion and high concentration (1000 mg L−1) inhibition. Oxidative stress was responsible for the growth inhibition at GO concentration of 1000 mg L−1, as suggested from great stimulation in the activities of antioxidant enzymes and MDA content in roots or leaves. Superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) activities were highly correlated with MDA levels (r2 = 0.963, 0.984, and 0.960, respectively). GO exposure caused significant concentration-dependent membrane depolarization in roots, and significantly inhibited H+ efflux and extracellular Ca2+ influx in root cap.