New research indicates that when plant leaves come into physical contact, they establish a biological signalling network that enhances their resilience to environmental stressors, particularly excessive light. This study, which is currently available on the preprint server BioRxiv but has not yet undergone peer review, suggests that plants can better withstand intense light exposure when they are in close proximity to one another.
The study focuses on the ability of plants to endure excessive light without incurring severe damage, such as leaf lesions. Researchers measured this damage by assessing ion leakage from the leaves. A plant exhibiting greater resilience will show reduced ion leakage compared to one that is more sensitive. According to Ron Mittler, a phytologist at the University of Missouri, “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.”
This latest research builds upon findings from a 2022 study that showed plants can transmit electrical signals through physical contact. The current study aimed to explore whether this touch also enhances the plants’ tolerance to stress. To achieve this, the team utilized the small weed-like plant, Arabidopsis thaliana, arranging one group to maintain leaf-to-leaf contact while another group was kept apart.
Researchers subjected the plants to bright, intense light, akin to harsh sunlight, and subsequently measured the damage. They evaluated ion leakage from the affected tissues and the accumulation of a pigment called anthocyanin, which indicates stress in plants. Results showed that plants in contact displayed lower leaf damage and reduced anthocyanin levels, while those grown in isolation exhibited significantly higher anthocyanin accumulation.
Mittler explained that if one plant experiences stimulation or stress, it sends a signal to all neighboring plants that it is in contact with, prompting them to become more tolerant of stress. To investigate the mechanisms behind this phenomenon, the team employed genetically modified plants incapable of transferring chemical signals. The experimental setup involved three plants: a transmitter, a mediator, and a receiver. When the mediator was replaced with mutant plants, the receiver plants did not receive protective signals against stress.
This research also uncovered the role of hydrogen peroxide secretion in enhancing resilience. It highlights the cooperative behavior of plants, which typically compete for resources such as space, light, and nutrients. Mittler posits that “If you grow under harsh conditions, you better grow in a group. If you grow under really ideal conditions with no predators, with no stressors, then you better grow individually.”
Piyush Jain, a plant biologist at Cornell University, who contributed to the study, praised the experimental design, stating it “addresses a longstanding question: whether chemical signaling and electrical signaling are responsible for increased resilience to excessive light stress.”
As this study awaits peer review, it opens new avenues for understanding the complex interactions between plants and their environments, shedding light on the previously underexplored pathways of plant-to-plant communication.
