Plants growing close together can alert one another to incoming stress, helping neighbouring plants survive conditions that would otherwise cause serious damage.
In experiments with thale cress (Arabidopsis thaliana), researchers grew plants either alone or tightly packed so their leaves touched. When exposed to intense light, isolated plants suffered severe damage, while crowded plants coped far better. Within one hour, closely growing plants activated more than 2,000 genes linked to protection against multiple stresses, whereas isolated plants showed little additional gene activity.
The findings suggest 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. For the first time, researchers demonstrated that hydrogen peroxide can move between plants, acting as an alarm signal that helps surrounding plants prepare for stress before damage occurs.
