Plants growing close together can alert one another to environmental stress, improving their chances of survival. Experiments with thale cress (Arabidopsis thaliana) showed that crowded plants activated strong defence responses when exposed to intense light, while isolated plants suffered severe damage.
Within an hour, densely packed plants switched on more than 2,000 genes linked to stress protection, whereas isolated plants showed little response. Researchers found that stressed plants released hydrogen peroxide, a chemical signal that travelled between neighbouring plants and triggered defensive gene activity. This study provides the first evidence that hydrogen peroxide can act as a warning signal passed directly from one plant to another.
