Plants growing close together can warn one another about 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 packed closely so their leaves touched. When exposed to intense light, isolated plants suffered heavy damage, while crowded plants coped far better by rapidly activating protective responses.
Within one hour, densely grown plants switched on more than 2,000 genes linked to defence against multiple stresses. Isolated plants showed little change in gene activity, suggesting they lacked early warning signals.
The study indicates that stressed plants send signals to neighbours. Crowded plants released hydrogen peroxide, a molecule known to trigger defence responses. Crucially, this was the first evidence that hydrogen peroxide can pass between plants, allowing them to prepare collectively for incoming stress.
