Plants growing close together can warn one another about incoming stress, helping nearby plants 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. In contrast, crowded plants coped far better, 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, while isolated plants showed little additional gene activity. The findings suggest that stressed plants send warning signals to their neighbours.
The study identified hydrogen peroxide as the key signal. While the molecule is already known to trigger defensive responses within plants, this is the first evidence that hydrogen peroxide can move between plants, acting as a shared alarm that prepares surrounding plants for stress before damage occurs.
