▎ 摘　　要

In various fields, much attention has been paid to graphene oxide (GO) nanosheets as a novel engineered nanomaterial. Understanding the interactions between GO and plant cells is critical for evaluating GO nanotoxicity, but the relevant information is largely lacking. Herein, it was discovered that GO nanosheets enveloped algal cells and formed blister-like nanostructures and bridge-like microstructures with cell exudates. Nitrogen-containing chemicals were shown to be responsible for the adhesion of GO to cellular surfaces. GO entered cells and damaged organelles. The two obvious alterations were plasmolysis and an increase in the number of starch grains. A reduction of cell division, aggregation of the chromatin and damage to the chloroplast structure were also observed. Compared with bulk-activated carbon, GO inhibited cell growth, enhanced the generation of reactive oxygen species (ROS) and disrupted antioxidant enzymes. Furthermore, GO caused metabolic disturbances linked to key biological processes. Carbohydrate and amino acid metabolisms were inhibited, and the ratios of unsaturated to saturated fatty acids were increased. The flux of nitrogen metabolism changed from amino acids to cadaverine and urea. These findings close a gap in understanding the phytotoxicity of nanomaterials. (C) 2014 Elsevier Ltd. All rights reserved.