Plants growing close together can alert one another to environmental stress, improving their chances of survival.
In experiments with thale cress (Arabidopsis thaliana), scientists compared plants grown in isolation with those 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 multiple stresses. Isolated plants showed little change in gene activity.
The findings suggest that stressed plants send warning signals to nearby neighbours. The study identified hydrogen peroxide as the key signal, released by crowded plants and passed between them.
This is the first evidence that hydrogen peroxide can move from one plant to another, triggering shared defensive responses before serious damage occurs.
