Plants growing close together can warn one another about 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 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 suggest that stressed plants send warning signals to their neighbours. The study showed that crowded plants released hydrogen peroxide, a molecule known to trigger defence responses. Importantly, this was the first evidence that hydrogen peroxide can pass from one plant to another, allowing plants to alert nearby companions and prepare them for incoming stress.
