Plants growing close to each other can warn each other about stresses in their lives.
Thale cress (Arabidopsis thaliana) plants were grown on their own or crowded so close together they were touching each other. When all the plants were then stressed with intense light, the isolated plants suffered severe damage, but the crowds of plants were able to cope with the stress. In fact, it just took an hour for the crowded plants to switch on more than 2,000 of their genes that were involved in protecting against a host of different stresses; in contrast, the isolated plants showed little sign of any extra gene activity.
Some sort of signal must have passed between the crowded plants to get them to defend themselves. Plants are well known for passing messages with airborne chemicals, and the crowded thale plants were found to release hydrogen peroxide, a chemical known to tell a plant to gear up its defences against all sorts of stresses. But the recent study was the first time that hydrogen peroxide was found passing from one plant to another to tell them to prepare their defences.
