Plants growing close together can alert one another to environmental 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 densely packed so their leaves touched. When exposed to intense light, isolated plants suffered severe damage, while crowded plants coped much better. Within an hour, densely grown plants activated more than 2,000 genes linked to protection against a wide range of stresses, whereas isolated plants showed little extra gene activity.
The findings indicate that stressed plants send warning signals to neighbours. The study showed that crowded plants released hydrogen peroxide, a molecule known to trigger defensive responses. Crucially, this was the first evidence that hydrogen peroxide can pass from one plant to another, acting as a shared alarm that prepares surrounding plants for stress before damage occurs.
