For more than twenty years, nanotechnologies have seen exponential growth in use and are now found in nearly all sectors. Carbon nanotubes (CNTs) are one of the most widely used nanomaterials due to their unique optical, mechanical, electrical and thermal properties. CNTs may be released into the environment during production, use, destruction, reuse or potential accidents such as spills. Plants are important potential receptors given that they are at the base of the food chain and can be particularly impacted by multiple exposure routes as they are at the interface between three environmental compartments; air, soil and water.

CNTs can be described as seamless rolled layers of graphene forming nanotubes. CNTs can be formed of one layer (Single Walled CNTs), two layers (Double Walled CNTs) or more (Multi Walled CNTs). Accordingly, their diameter can vary from below 1 to ca. 100 nm. Their length can also differ (from <1 to 100 microns or even more). Finally, CNTs can be functionalized by attaching chemical groups to their surface. These different parameters can modify their properties and their interactions in the environment. In “safer by design” production, it is important to understand how different CNT physico-chemical parameters will influence their behaviour and their impacts on ecosystems. In this study, we tested the influence of CNT functionalization, length and outer diameter on their impacts on the crop plant canola.

Five different types of CNTs were used for this experiment: raw and oxidized DWCNTs, raw and oxidized MWCNTs, and short length raw MWCNTs. An agricultural sandy loam soil was contaminated using these five CNTs at three concentrations (0.1, 10 and 100 mg/kg). Different morphological and metabolism biomarkers were evaluated at the end of the five-week exposure. Nutrient concentrations in the leaves and roots were analysed by ICP-OES. Biomacromolecular changes in leaves were studied using Fourier transformed infra-red spectroscopy by developing a chemometric analysis. Candidate genes expression was analysed in the leaves using qPCR.

The results show that the different physico-chemical parameters of CNTs significantly influence their impacts on canola plants. Only the DWCNTs (smaller diameter) had impacts on canola. Functionalization also influences the effects of CNTs. Raw DWCNTs inhibited several development parameters of the canola, such as the germination rate, while oxidized DWCNTs led to an enhanced development: increased height, foliar surface or biomass. This was not related to nutrient concentrations or plant water content. Additional data on biochemical and molecular response of the plants to exposure will be presented.