November 2009

NANOTECHNOLOGY:

Sprucing Up Your Garden with Carbon Nanotubes

Update May 2013: Today I was forwarded an unusual e-mail from “Jaime A. Teixeira da Silva.” Apparently this person sent the following note to the National Association of Science Writers, demanding that my blog post be removed:

“Dear NASW,

I wish to bring to your attention that you are supporting the promotion of science in a paper that was formally retracted. Basically, the paper was retracted based on academic fraud.

Thus, by advertising their work, you are supporting fraud and advertising it as being validated research.

I recommend that the PDF you have posted be removed http://www.nasw.org/users/mslong/2009/2009_11/Nanotubes.htm

Sincerely,

Jaime A. Teixeira da Silva”

Dude (ignoring the fact that it’s not a “pdf”), all you had to do was let me know that the original article was retracted. This is the link to the publisher’s retraction notice. Apparently the research results are real, but some of the data was published in other journals without proper attribution.

Read on for a discussion of the manuscript.

Synthetic nanomaterials (something with one dimension that's approximately one billionth of a meter) are everywhere. Among many other examples, cobalt oxide nanoclusters can convert water into oxygen, silica nanoparticles are being developed for diabetes management, and chemically modified gold nanoparticles can be used to test for melamine in purified milk.

Note that some nanomaterials are dangerous. Admittedly, the fear of Armageddon brought about by self-replicating nanomachines that suffocate the planet is a bit ridiculous (at present).

On the other hand, there are legitimate safety concerns about nanomaterials. As one example, titanium nanofilaments can be toxic, emphasizing the need for rigorous toxicity testing of nanomaterials, not just evaluations of their useful chemical and physical properties.

Keeping this in mind, Alexandru Biris (University of Arkansas) and coworkers have reported a startling use for carbon nanotubes. They found that carbon nanotubes can help tomato plants grow.

Carbon nanotubes: Letting in the water.

The scientists supplemented a standard growth medium with carbon nanotubes. They observed that tomato plant seeds incubated in this supplemented growth medium sprouted leaves and roots within three days, faster than in standard growth medium.

Additionally, 90% of the seeds in the supplemented growth medium had started to grow into tomato plants after 20 days. This is more than the 70% observed in standard growth medium.

After 27 days, the tomato plants grown with carbon nanotubes also exhibited 2.5 times more mass (roots, stems, and leaves) than the standard tomato plants. Tomato plants therefore start their growth, and continue to grow, faster when carbon nanotubes are added to the growth medium.

What explains these enhanced growth results? The scientists found that the seeds placed in carbon nanotubes had almost 50% more water in them than the standard seeds.

The scientists suspect that the extra water enters the plant seeds and roots via the carbon nanotubes (the nanotubes punch holes in the plants, letting in water), facilitating growth. However, a detailed biochemical study has yet to be performed.

Further development.

As the scientists note, changing the surface composition of the nanotubes, or changing the plant species, may give totally different results. There are undoubtedly some plants that don't like to be harpooned.

You shouldn't be dumping carbon nanotubes on your vegetable garden as "fertilizer" yet; these are preliminary observations only, and frankly may never be put into practice outside of a laboratory. They could definitely be useful though, for example in accelerating the growth of plants used for biofuel production.

for more information:
Khodakovskaya, M., Dervishi, E., Mahmood, M., Xu, Y., Li, Z., Watanabe, F., & Biris, A. S. (2009). Carbon Nanotubes Are Able To Penetrate Plant Seed Coat and Dramatically Affect Seed Germination and Plant Growth ACS Nano, 3 (10), 3221-3227 DOI: 10.1021/nn900887m