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 protective responses.
Within just one hour, densely grown plants switched on more than 2,000 genes linked to defence against a wide range of stresses. Isolated plants, by contrast, showed little increase in gene activity, suggesting they lacked access to warning signals.
The study found that crowded plants released hydrogen peroxide, a molecule known to trigger defensive reactions in plants. For the first time, researchers showed that this chemical can pass between neighbouring plants, acting as an early warning system that prepares them for stress before serious harm occurs.
