Plants growing close together can warn one another about incoming stress, helping nearby 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 just one hour, densely grown plants switched on more than 2,000 genes linked to protection against a wide range of stresses. Isolated plants, by contrast, showed little increase in defensive gene activity.
The findings suggest that stressed plants send warning signals to those nearby. The study identified hydrogen peroxide as the key signal, a molecule known to trigger plant defence responses. For the first time, researchers showed that hydrogen peroxide can pass between plants, acting as a shared alarm that allows neighbours to prepare for stress before serious damage occurs.
