Weeding Out Land Mines

Gene-Altered Plant Blushes When Roots Sense Explosives

PETER GWIN / National Geographic v.207, n.3, 1mar2005

A lethal problem just might be solved with a leafy approach: using genetically modified plants to find land mines. Scientists at the Danish firm Aresa Biodetection and the University of Copenhagen have produced a variety of thale cress (Arabidopsis thaliana, right) that turns from green to red (below) when its roots encounter nitrogen dioxide—a by-product of land mines that gradually evaporates from buried explosives.

Thale cress naturally changes color under certain conditions, says Aresa^'s founder Carsten Meier. "We manipulated the plant^'s genetic switch so that this variety changes color when it senses nitrogen dioxide." A range of experiments have been performed with thale cress, including growing it in soil laced with a TNT solution and in boxes containing land mines. Soon Meier hopes to test the plant on live mines in Bosnia.

"It's an interesting idea," says land mine expert Bill Reid, who still notes several drawbacks, among them the costs of defoliating minefields before sowing the plants, and watering in arid climates. But Meier thinks further research may yield strains able to overcome such challenges.

Scientists have tried many techniques to locate the world's estimated 60 million land mines, from training rats to sniff out explosives to using honeybees to collect chemical samples. As yet, says Reid, "there is no silver bullet."