Genetically engineered plants turn red when growing over a mine.
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 leaves of the plant change from green to red after three to five weeks of growth in the presence of this gas. "They are easy to spot," says Carsten Meier of the University of Copenhagen, Denmark, who served as scientific adviser to Aresa, the Danish company that developed the plant.
The team doesn't yet know how sensitive the plant is to nitrogen dioxide, and therefore are not sure how much of the gas is needed to make it turn red.
But they hope the technique will prove useful in field tests. If it does, it should substantially speed up the process of de-mining. Currently, one person can check and clear just two square metres of land a day, says Meier. "Landmines are laid down faster than they are removed," he adds.
"This is a great idea," says Richard Vierstra, a horticulture scientist at the University of Wisconsin, Madison, who works on Arabidopsis. He points out that the plant is quite shallow-rooted, and so will only detect mines near the surface. But this is where most landmines are found, says Geir Bjoersvik, head of the mine action unit for the landmine-removing project at Norwegian People's Aid.
Red marks the spot
The researchers achieved the colour change by manipulating the naturally occurring machinery that makes autumn leaves red. The genes that produce this red pigment, called anthocyanin, are normally switched off during most of the year. But the team inserted a gene that turns on this red pigment-making apparatus in the presence of nitrogen dioxide.
Aresa is now developing spray guns that can sow the seeds cheaply and safely. They are also working on plants that will respond to other environmental pollutants such as cadmium and nickel, so that soil can be cleaned up once these heavy metals have been detected.
The team has also taken steps to ensure that the genetically engineered plant won't spread in the wild. They have removed the gene for an important growth hormone, so that the plant needs a specially designed fertilizer in order to grow.
But Ben Ayliffe, spokesman for the environmental global campaigning organization Greenpeace, is not convinced that technology is the best solution to the problem of landmines. "There are already effective ways of dealing with landmines but there is a lack of political will to address the problem," he says. The ultimate solution, he says, is to stop people from laying mines in the first place.