Synergistic effects of glyphosate and multiwall carbon nanotubes on Arabidopsis thaliana physiology and metabolism

Agricultural chemicals have the potential to become pollutants that adversely affect plant growth. Interactions between these compounds are likely, but potential synergies are under-researched. Multiwall carbon nanotubes are increasingly finding novel uses in agriculture, as delivery mechanisms and as slow-release fertilizers. There is potential for nanotubes to interact with other agricultural chemicals in unpredictable ways. To investigate this possibility, we examined interactions with glyphosate, a widely used herbicide that is also attracting increasing concern over its potential for non-target effects. Here we examined potential synergistic effects on hydroponically grown Arabidopsis thaliana. Single treatments did not affect plant growth significantly, or did only mildly. However, combined treatment significantly affected both plant root and shoot growth. High-level content of malondialdehyde and up-regulated of metabolic antioxidant molecules in plant indicated that combined group caused the strong oxidative damage, while the decreased of antioxidant enzyme activities indicated an imbalance between reactive oxygen species (ROS)and the antioxidant defense system due to the continuously generated ROS. Besides, several intermediate metabolites of unsaturated fatty acids synthesis pathways were up-regulated in combined treatment, which clarified that combined group changed membrane components. The increase of intermediate metabolites in combined group also reflected more energy consumption in the repairment of the disrupt of combined treatment. The synergistic effect observed was attributed to the accumulation of glyphosate resulting from permeability and transportability of the carbon nanotubes. Overall, the risk of nanotube-herbicide interaction suggests a caution use of nanotubes in agricultural applications.