Plants growing close together can warn one another about incoming stress, helping nearby neighbours survive conditions that would otherwise cause serious damage.
In experiments with thale cress (Arabidopsis thaliana), researchers grew plants either in isolation or packed closely so their leaves touched. When exposed to intense light stress, isolated plants suffered heavy damage. Crowded plants, however, coped far better by rapidly activating protective mechanisms.
Within just one hour, densely grown plants switched on more than 2,000 genes linked to defence against a wide range of stresses, while isolated plants showed little extra gene activity. This rapid response suggests that stressed plants transmit warning signals to those nearby.
The study identified hydrogen peroxide as the key messenger. While the chemical is already known to trigger defensive responses within individual plants, this research provides the first evidence that hydrogen peroxide can pass from one plant to another. By sharing this signal, plants growing together can collectively prepare for stress before serious damage occurs.
