“Plants to Uncover Landmines”
According to this news article: “A genetically engineered plant that detects landmines in soil by changing colour could prevent thousands of deaths and injuries by signalling where explosives are concealed. The plant, a modified version of thale cress (Arabidopsis thaliana), is sensitive to nitrogen dioxide gas, which is released by underground landmines.”
The Danish biotech company, Aresa Biodetection, responsible for this early work, never really achieved practical success with this approach, however. “In September 2008, the Danish firm, Aresa Biodetection that had been primarily behind the research and promotion of this methodology announced that it had discontinued the work behind this project.” (from: “Comparison of Landmine Detection Methods”)
But the story didn’t end there….
Phyto-detection of Explosives
In 2017, a paper was published in Nature Materials (see Ref. 3 below), which the BBC reported as ‘Bionic’ plants can detect explosives and further described as; “Scientists have transformed the humble spinach plant into a bomb detector.”
This BBC article briefly summarized the research as follows: “By embedding tiny tubes in the plants’ leaves, they can be made to pick up chemicals called nitro-aromatics, which are found in landmines and other buried munitions. The scientists implanted nanoparticles and carbon nanotubes (tiny cylinders of carbon) into the leaves of the spinach plant.
They then delivered the nitro-aromatics into the water taken up by the roots and directly to the leaves in droplets. It takes about 10 minutes for the spinach to take up the water via the roots into the leaves.
To read the signal, the researchers shine a laser onto the leaf, prompting the embedded nanotubes to emit near-infrared fluorescent light.
This can be detected with a small infrared camera connected to a small, cheap Raspberry Pi computer. The signal can also be detected with a smartphone by removing the infrared filter most have.”
DARPA has also gotten into the act: Nature’s Silent Sentinels Could Help Detect Security Threats. But, to date, no real-world applications of this technology are evident.
Recently, a group of investigators (see Ref. 4 below) have provided evidence that soil contaminated with explosive compounds, such as TNT and RDX, may be able to be detected by monitoring chemical stress-induced changes in natural vegetation. This monitoring would be conducted by using remote sensing of vegetation with aerial-based hyperspectral systems, reminiscent of a proposal for using changes in vegetation to detect dead bodies (see previous post).
However, as with other attempts to use plants to detect explosives, this research amounts to merely proof of concept, with no practical, real-world results.
Phyto-remediation of Explosives
Though the phytodetection of explosives may prove, in the end, to be somewhat impractical, using plants to help detoxify explosive compounds contaminating soils looks a lot more promising.
In a recent review of this subject, Rylott and Bruce (see Ref. 5 below) report that: “Scientists have been working on bioremediation projects in this area for several decades, characterizing genes, biochemical detoxification pathways, and field-applicable plant species.” They conclude that much progress has been made “…in understanding the fundamental biochemistry behind the detoxification of explosives, including new shock-insensitive explosive compounds; how field-relevant plant species have been characterized and genetically engineered; and the major roles that endophytic and rhizospheric microorganisms play in the detoxification of organic pollutants such as explosives.”
If biotechnologists can overcome the hurdles inherent in introducing GMO plants/microbes into the natural environment, then plants may indeed play important roles in remediating environments contaminated with explosive compounds.
1. Could plants be used as sensors? a blog post (mainly for historical reference) at www.engineering.com (1/22/2013)
2. Plant Sentinel Technology website for Dr. June Medford’s lab at Colorado State University
3. Wong, M. H., et al. (2017) “Nitroaromatic detection and infrared communication from wild-type plants using plant nanobionics.” Nature Materials, Vol. 16, pp. 264–272. (Abstract)
4. Manley, P. V., et al. (2019) “Remote Sensing of Explosives-Induced Stress in Plants: Hyperspectral Imaging Analysis for Remote Detection of Unexploded Threats.” Remote Sensing, 11, 1827; doi:10.3390/rs11151827. (Full Text)
5. Rylott, E. L. and N. C. Bruce (2019) “Right on target: using plants and microbes to remediate explosives.” International Journal of Phytoremediation, Vol. 21, pp. 1051-1064; doi:10.1080/15226514.2019.1606783. (Full Text)