Plants growing close together can warn one another about incoming stress, helping their 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, while crowded plants coped far better by rapidly activating protective mechanisms.
Within one hour, densely grown plants switched on more than 2,000 genes linked to defence against multiple stresses. Isolated plants, by contrast, showed little change in gene activity, suggesting they received no early warning.
The findings indicate that stressed plants send signals to nearby neighbours. The study identified hydrogen peroxide as the key messenger, released by crowded plants to alert others to prepare their defences. This marks the first evidence that hydrogen peroxide can pass between plants, acting as a shared alarm system that boosts survival under harsh conditions.
