Toxicity and translocation of graphene oxide in Arabidopsis plants under stress conditions

In the present study, we investigated the toxicity and translocation of graphene oxide (GO) in the μg L−1 range in Arabidopsis plants under both normal and stress conditions. Exposure to GO for 4 weeks did not cause adverse effects on the development of Arabidopsis seedlings. In contrast, the combined exposure to GO and PEG 6000 (20%) or NaCl (200 mM) resulted in a more severe loss of morphology, decrease in fresh weight or root length, and increase in root-to-shoot ratio in Arabidopsis seedlings compared with exposure to stress alone. The combined exposure to GO and PEG 6000 (20%) or NaCl (200 mM) resulted in a greater increase in hydrogen peroxide content or membrane ion leakage, decrease in superoxide dismutase activity or catalase activity, and induction of reactive oxygen species production in Arabidopsis seedlings compared with exposure to stress alone. The combined exposure to GO and PEG 6000 (20%) or NaCl (200 mM) induced more severe alterations in expression patterns of genes required for development, abiotic stress, and membrane ion leakage in Arabidopsis seedlings. Moreover, under stress conditions, more GO was distributed in Arabidopsis seedlings and GO was translocated from roots to leaves. We hypothesize that, under stress conditions, GO may induce oxidative stress and membrane ion leakage, which may in turn induce GO translocation from the roots to the leaves. Our results will be useful for understanding toxicity and translocation of GO under different environmental conditions.