Proc. Natl Acad. Sci. USA doi:10.1073/pnas.1008856108 (2010)

Understanding the impact of engineered nanomaterials on plants and the environment is a major challenge in nanotechnology. Two years ago, for example, Mariya Khodakovskaya of the University of Arkansas and colleagues showed that single-walled carbon nanotubes can lead to the enhanced growth of tomato plants. Now Khodakovskaya and colleagues at Arkansas have explored the effects of nanoparticles on plants in greater detail using a combination of genetic, photothermal and photoacoustic techniques.

The Arkansas team started by growing tomato plants in growth media that contained one of four forms of carbon — active carbon, few-layer graphene, single-wall nanotubes and multiwall nanotubes. The multiwall nanotubes had the biggest impact on the growth of the plants so the team subjected roots, leaves and fruit from these plants to further analysis, and compared the results with a control sample that did not contain any nanotubes, after both had been growing for ten days.

Photothermal and photoacoustic techniques revealed the presence of the nanotubes in the roots, leaves and fruit to the level of single nanoparticles and cells. The genetic analysis revealed effects not seen in the control sample, such as activation of a number of stress-related genes, including the gene for tomato water-channel protein. The activation of this gene had a significant impact on the germination of the seeds and the growth of the seedlings.