A new study has found that when plant leaves physically touch, they form a biological signaling network that allows them to warn each other about impending stress. This mechanism can increase plants’ resilience to intense light—one of the most common environmental challenges.

How Plants Respond to Excess Light

The study, which has not yet been peer-reviewed and is published on the BioRxiv platform, defined resilience as a plant’s ability to withstand excess light without suffering serious damage, such as leaf injury. Scientists assessed the extent of damage by measuring ion leakage from the leaves: the less leakage, the greater the plant’s resistance to light stress.

The Impact of Physical Contact Between Plants

Ron Mittler, a plant physiologist at the University of Missouri, noted that plants in physical contact with each other become more resistant to light stress compared to those grown alone. This was confirmed by comparing groups of plants whose leaves touched with those that did not have contact.

Experimental Methodology

The researchers used the small weed Arabidopsis thaliana in their experiments. One group of plants was arranged so that their leaves touched, while another group was kept apart. After establishing physical contact, the plants were exposed to bright, intense light simulating harsh sunlight. The scientists then measured damage by assessing ion leakage and the accumulation of anthocyanins—pigments that indicate stress.

The results showed that plants in contact had less leaf damage and lower anthocyanin levels. In contrast, plants grown alone exhibited significantly higher anthocyanin levels. Mittler pointed out that if one plant experiences stress, it sends a signal to all the plants it touches, making the entire group more resilient.

The Role of Chemical and Electrical Signals

To understand the signaling mechanisms, the team used genetically modified plants incapable of transmitting chemical signals. In the experiment, plants were arranged in a chain of three: a sender, an intermediary, and a receiver. If the intermediary was a mutant plant, the receiver did not gain protection from stress. This confirmed that the release of hydrogen peroxide plays a key role in boosting resilience.

Cooperation Among Plants

The study highlights the cooperative side of plant life. While plants usually compete for space, light, and nutrients, under stress they can unite to improve survival. Mittler sees this as an evolutionary compromise: in harsh conditions, it’s more advantageous to grow in groups, while in ideal conditions, growing alone is preferable.

Piyush Jain, a plant biologist from Cornell University who participated in the study, noted that the experimental design helps to better understand the little-studied pathways of aboveground communication between plants and addresses the longstanding question of the role of chemical and electrical signaling in resistance to light stress.