Talking plants may be able to warn each other

Some plants may be able to "talk" among themselves and warn each other about impending danger, according to new research.

Scientists at Kyoto University in Japan have discovered that some plants not only release chemicals to make them less tasty to attacking bugs, they also warn each other of the impending danger.

The researchers let hungry spider mites loose on an unsuspecting group of lima-bean plants and found they responded with five separate defence mechanisms.

As soon as the mites arrived the first injured plant activated a gene that released a chemical, changing the plant's flavour and making it less attractive to the mites.

More genes were then switched on, producing other chemicals that drifted away from the plant like a distress signal.

This caused all the other nearby lima-bean plants to answer the call and begin giving off the same chemicals even before any more mites arrived, according to an account of the research published in the science journal, Nature, today.

Some of these act like insect repellent, helping to keep the mites out of the neighbourhood.

Others have the opposite effect, serving as irresistible attractants that coax in a predatory form of mite that enjoys lunching on the spider mite.

The Japanese research team also discovered that the plants could tell the difference between damage caused by crushing and damage caused by munching insects.

They intentionally crushed leaves and stems to see if the lima would attempt to defend itself and warn the other plants.

They found the injured bean plant released chemicals, but all the other plants ignored the signals, somehow realising the warning was false and posed no real threat.

The Japanese researchers believe this plant-to-plant communication might be useful in encouraging crops to protect themselves against insect attack without the use of synthetic sprays.

If the plants could be tricked into sending out the warning signals, then the whole crop would become less susceptible to chewing mites.

And if it works for lima beans, then who is to say that peas or tomatoes or spinach don't have their own language and early warning system?