Plants, photosynthetic, eukaryotic, uni- or multi-cellular organisms of the kingdom Plantae form a large part of the foundation of all life on our planet. Complex, multi-cellular life forms would not be possible without them. The Carbon and Nitrogen Cycles are inherently dependent on the biological activity of plants as is the production of oxygen, the Veda Pela of life. Everything we eat is derived directly or indirectly from plants. Plants and the products extracted from them permeate every facet of our lives from the medicines we take to the clothes we wear and the buildings we live in. They clean our air and our water, and to some extent regulate the weather. Plants live a mostly quotidian existence but recently their adaptability and genetic malleability have thrust them into the spotlight as the latest entry in the arsenal of biological anti-terrorism tools. They are being tested as bomb detectors. Mind boggling is an understatement.
Previously, dogs, honey bees, spectrometry, X-ray machines and other such methods and mechanisms were used to detect explosives and their constituent components. Bomb detecting plants would open up new avenues of detection devices capable of unobtrusively monitoring for chemical signatures associated with explosives and their constituent components, as well as environmental pollution. Similar studies have been done using other organisms to detect chemical pollutants in water, e.g. Zebra fish that glow when exposed to certain pollutants.
Recently, biologist June Medford and her teammates at the Colorado State University undertook an extensive research to determine the feasibility of developing plants that could help the world fight terrorism. They redesigned naturally occurring plant receptor proteins using a computer programme. These protein receptors were then modified to function in the plants by incorporation in the cell wall. They then determined that the modified plants were able to detect pollutants in the local vicinity, monitoring either the air or soil for specific chemical trails, and curtailing chlorophyll production, turning white in the process. The plants did this in a matter of hours. The research team hopes to shorten that time to a few minutes.
During her research, Medford discovered that tobacco plants are ever better at detecting the airborne substances than dogs and this trait occurs naturally in plants while dogs must be specially trained to perform this task. She also observed some plants in her lab which turned pale white when exposed to TNT (Trinitrotoluene), which is a powerful explosive often used in terrorist bombs.
Medford said, “The idea comes directly from nature. Plants cant run or hide from threats, so theyve developed sophisticated systems to detect and respond to their environment. Weve taught plants how to detect things were interested in and respond in a way anyone can see, to tell us there is something nasty around. And we did this by modifying the way the plants proteins process chlorophyll.”
The phenomena in plants that provides a base for this ability is that plants have receptors in their DNA that responds naturally to threatening stimuli. For example, if a bug chews on the leaves, the plant releases a series of signaling chemicals called Turpenoids. The release of these chemicals provide evidence that the plants are being subjected to some type of threatening stimuli. It works as an alarm signal. The biologists at the Baker and Hellinga Laboratories used the computer program to redesign these receptors and targeted them to the plant cell wall for the detection of explosive compounds in the air and soil. When the plant detects the target chemical(s), the receptors switch on and change color from green to white. When the chemical stimulants are removed, it turns green again.
The best part about the invention is that these computer detection traits can be induced in any plant, and they have the ability to detect a multitude of explosive compounds at the same time. The color changes the plants undergo can be detected by satellites. The detection of major changes in plants or plant populations takes more time, perhaps 24 to 48 hours but a spectral imaging system already exists that is capable of detecting the major changes in plants.
Medford is now working to decrease the detection time so that the plants respond in a fraction of a second. This will help ensure the safety of the areas where they are being grown or are positioned. Without a shortened response time this ability will be less useful.
One a problem Medford must deal with is that of ammonium nitrate, a common chemical used for making IEDs (Improvised Explosive Devices) in Afghanistan and found in fertilizers. To mitigate this issue Medford wants to introduce the bomb detecting seedlings at first. She expects that it will be less than $100,000 to $200,000 that a backscatter “junk scanner” costs.
So the main questions that must be answered are;
Can these plants detect all the explosives?
Are they able to detect the explosives within the short time?
Is there any way by which we can monitor the activity of the plants from a longer distance?
Can we make such plants response independent of the concentration of the chemicals?
These questions present a definite challenge for the biologists. They hoping further research will provide the answers.