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 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 change in gene activity.
The findings indicate that stressed plants send warning signals to nearby neighbours. The study showed that crowded plants released hydrogen peroxide, a molecule known to trigger defence responses. Crucially, this was the first evidence that hydrogen peroxide can move from one plant to another, acting as an alarm signal that prepares surrounding plants for stress before damage occurs.
