Plants, like humans, communicate with one another as soon as they detect a threat or attack in their surroundings. Scientists have known about this phenomenon since the 1980s, when they identified at least 80 species that defend themselves during times of crisis. However, the exact mechanism by which plants receive such danger signals from their neighbors remains unknown.
Now, a team of Japanese scientists has not only solved this puzzle but also captured the communication between plants in an incredible video. In a study published in Nature Communications, molecular biologists Yuri Aratani and Takuya Uemura from Saitama University in Japan demonstrated how these plants respond when they detect danger.
Scientists experimented by setting off caterpillars on tomato plant leaves and a common weed known as Arabidopsis thaliana. To better understand the impact on the neighboring plant, the compounds were concentrated in a plastic bottle and pumped onto the recipient plant at a constant rate.
Furthermore, the recipient Arabidopsis plant was genetically engineered with a biosensor that fluoresced green when calcium ions were detected.
Undamaged plants responded to injured neighbors by displaying calcium signaling across their extended leaves
Undamaged plants in the video responded to messages from injured neighbors, displaying calcium signaling across their extended leaves. The researchers discovered that compounds Z-3-HAL and E-2-HAL induced calcium signals in Arabidopsis by analyzing airborne compounds.
Using Arabidopsis plants engineered with fluorescent sensors in specific cells, they discovered that guard cells (which form stomata), mesophyll cells (inner leaf tissue), and epidermal cells (outermost layer) were the first to respond to danger signals.
When exposed to Z-3-HAL, guard cells first produced calcium signals, followed by mesophyll cells. Furthermore, pre-treating plants with a phytohormone that closes stomata reduced calcium signaling, indicating that stomata function as the plant’s ‘nostrils.’
“We have finally unveiled the intricate story of when, where, and how plants respond to airborne ‘warning messages’ from their threatened neighbors,” says Masatsugu Toyota, a molecular biologist at Saitama University in Japan and senior author of the study.
“This ethereal communication network, hidden from our view, plays a pivotal role in safeguarding neighboring plants from imminent threats promptly.”