Plants growing close together can alert one another to danger, helping nearby plants survive conditions that would otherwise cause serious damage.
In experiments with thale cress (Arabidopsis thaliana), researchers grew plants either in isolation or packed so closely that their leaves touched. When exposed to intense light, isolated plants suffered heavy damage, while crowded plants coped far better. Within an hour, closely grown plants activated more than 2,000 genes linked to protection against multiple stresses, whereas isolated plants showed little defensive response.
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 mechanisms. Crucially, this was the first evidence that hydrogen peroxide can move between plants, acting as a shared alarm that prepares nearby plants for stress before serious harm occurs.
