New research indicates that when plant leaves make physical contact, they form a biological signalling network that helps them warn each other of impending stress. This interaction enhances their resilience to environmental challenges, particularly excessive light exposure, a common stressor for many plant species. The findings, which are pending peer review, suggest that plants can significantly improve their ability to endure harsh conditions when in proximity to one another.
The study, conducted by a team led by Ron Mittler at the University of Missouri, examines the concept of resilience in plants. In this context, resilience refers to a plant’s capacity to withstand excess light without incurring serious damage, such as leaf lesions. Researchers measured the degree of damage by assessing ion leakage from the leaves; more resilient plants exhibited lower ion leakage when subjected to intense light conditions.
“We demonstrated that if plants touch each other, they are more resilient to light stress by comparing groups of plants that touch each other with groups that do not,” Mittler explained in an interview with New Atlas. This builds upon previous findings from a 2022 study which showed that plants can transmit electrical signals when in contact.
To explore whether physical touch enhances stress tolerance, the research team utilized the small weed-like plant, Arabidopsis thaliana. The experimental setup involved arranging two groups of these plants—one group maintaining leaf-to-leaf contact while the other was kept apart. After establishing this connection, the plants were exposed to bright, intense light similar to harsh sunlight.
Following this exposure, researchers evaluated the damage by measuring ion leakage from the affected tissues and the levels of a pigment known as anthocyanin, which accumulates in response to stress. The results revealed that plants in contact with one another experienced significantly lower leaf damage and reduced anthocyanin accumulation compared to their isolated counterparts, which showed markedly higher anthocyanin levels.
Mittler noted that when one plant experiences stress, it signals to all the other plants it touches, resulting in a collective increase in tolerance. This phenomenon suggests a cooperative aspect of plant behaviour, challenging the traditional view that plants solely compete for resources such as space, light, and nutrients.
To delve deeper into the underlying mechanisms, the researchers employed genetically modified plants that lacked the ability to transfer chemical signals. Their experimental configuration involved a sequence of three plants: a transmitter, a mediator, and a receiver. The results indicated that when the mediator was replaced with mutant plants incapable of signal transfer, the receiver plants did not gain the anticipated protection against stress. This setup also underscored the importance of hydrogen peroxide secretion in enhancing resilience.
Mittler’s findings highlight an evolutionary trade-off among plants. “If you grow under harsh conditions, you better grow in a group. If you grow under really ideal conditions with no predators and no stressors, then you better grow individually,” he stated.
Plant biologist Piyush Jain from Cornell University, who contributed to the study, praised the innovative experimental design, noting that it addresses a long-standing question about the role of chemical and electrical signalling in plant resilience to excess light stress.
Although this study has not yet undergone peer review, it is already available on BioRxiv, marking a significant step forward in understanding the complex interactions that occur among plants in their natural environments. The collaborative nature of plant communication opens new avenues for research and has implications for agricultural practices and ecosystem management.
