Plants growing close together can warn one another about incoming stress, helping their neighbours survive conditions that would otherwise cause serious damage.
In experiments with thale cress (Arabidopsis thaliana), researchers grew plants either in isolation or packed closely so their leaves touched. When exposed to intense light stress, isolated plants suffered heavy damage, while crowded plants coped far better by rapidly activating their defences.
Within one hour, densely grown plants switched on more than 2,000 genes linked to protection against many different stresses. Isolated plants showed little additional gene activity in comparison.
The findings suggest that stressed plants send warning signals to nearby neighbours. The study identified hydrogen peroxide as the key signal, a molecule known to activate plant defences.
For the first time, researchers showed that hydrogen peroxide can pass from one plant to another, acting as an alarm that prepares surrounding plants for stress before serious damage occurs.
