Graphene
oxide (GO) has shown enormous potential in applications
for improving crop yield and soil cultivation quality. However, in
heavy metal contaminated soil, the effect of GO on heavy metals and
the indirect toxicity of GO to plants remain unclear. In this work,
we reveal the GO-promoted cadmium (Cd) uptake by rice in a Cd-contaminated
soil system. The oxygen-rich functional groups and the large specific
surface area of monolayer GO result in strong Cd(II) adsorption (with
a maximum adsorption capacity of 265.8 mg/g), which significantly
change the existing forms of Cd(II) in the soil. In particular, GO
converts the inorganic-bound form Cd(II) that is not readily absorbed
by plants into the exchangeable form that is more available for plant
absorption. As a result, Cd(II) content in rice seedlings is increased
by 12.5% with the application of GO. Therefore, it can be concluded
that GO exhibited indirect toxicity to plants in heavy metal-enriched
soil.