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 alone or packed closely so their leaves touched. When exposed to intense light, isolated plants suffered heavy damage, while crowded plants coped far better. Within one hour, densely grown plants activated more than 2,000 genes linked to protection against multiple stresses, whereas isolated plants showed little change in gene activity.
The findings suggest that stressed plants send warning signals to their neighbours. The study showed that crowded plants released hydrogen peroxide, a molecule known to trigger plant defence responses. Crucially, this was the first evidence that hydrogen peroxide can pass from one plant to another, acting as an alarm signal that helps neighbouring plants prepare for stress before damage occurs.
