DARPA seeks 'smart plants' to protect soldiers

Forget the canary in the coal mine. The next sensor to detect chemical weapons may be the potted plant in your office.

Or rather, a plant genetically modified to detect chemical weapons, radiation from nuclear devices and other threats that waft through the air. DARPA's Advanced Plant Technologies, or APT, aims to genetically engineer "smart plants" that function as sensors.

"DARPA’s vision for APT is to harness plants’ natural mechanisms for sensing and responding to environmental stimuli and extend them to detect the presence of certain chemicals, pathogens, radiation, and even electromagnetic signals," according to a recent DARPA announcement.

"APT aims to modify the genomes of plants in order to program in these specific types of sensing and trigger discreet response mechanisms in the presence of relevant stimuli, and do so in a way that does not compromise the plants’ ability to thrive."

The idea isn't exactly new. Biologists have already proposed planting smart gardens at airports that could detect drugs and explosives. Others advocate using plants to detect pollutants in the air.

But for DARPA and the U.S. military, plant-based sensors are cheap, provide their own energy courtesy of the sun, can flourish in a variety of environments, and blend unobtrusively in the background. (When is the last time you noticed a potted plant?) Plants also naturally react to certain stimuli. Genetic engineering would allow the U.S. military to determine which stimuli spark a plant's reaction.

“Plants are highly attuned to their environments and naturally manifest physiological responses to basic stimuli such as light and temperature, but also in some cases to touch, chemicals, pests, and pathogens,” said Blake Bextine, DARPA's APT program manager.

While DARPA may be pushing the limits of biology, it will be more conservative on communications. APT will rely on current technology to remotely monitor plants. "Such systems are already capable of measuring plants’ temperature, chemical composition, reflectance, and body plan, among other qualities, from a standoff distance," the announcement states. "The APT program will not fund development of new hardware for this purpose."

DARPA officials admit there are challenges in keeping those leafy sensors alive, such as understanding how plants allocate their biological resources, and how they survive in the wild. "Past experiments of this type have reduced the fitness of modified plants by siphoning resources needed to sustain the plants," the agency notes. "APT will seek to improve how plants collect and distribute resources, and optimize their fitness so that modified plants thrive despite anticipated interactions with natural stressors such as microbes, animals, insects, and other plants."

Interestingly, DARPA says that the initial research will be performed in contained laboratories and greenhouses, and will "adhere to all applicable federal regulations with additional oversight from institutional biosafety committees." If the initial work proves successful, follow-up trials will be conducted under the auspices of the Department of Agriculture’s Animal and Plant Health Inspection Service.

DARPA appears to be anticipating an almost inevitable public backlash. Given the often-vociferous sentiment against genetically modified "Frankenfoods," there may well be protests against militarized plants, or fears among some that their ferns are spying on them. Earlier this year, a genetics scientist warned that DARPA's synthetic biology research could violate international environmental treaties and risk unanticipated effects on ecosystems.

On the other hand, DARPA points out that it is expensive and complicated to maintain networks of mechanical and electronic sensors. A genetically modified organism, or GMO, plant could be a much less expensive option for distributing sensors over a wide area.