Plants warn each other of danger, and now we can watch them | Explained Premium

Plants "eavesdrop" on conversations between other plants via green leaf volatiles (GLVs) released when injured. Scientists are exploring ways to use this process to fight pests without pesticides. A new study by Masatsugu Toyota reveals how plants respond to these warning signals, unlocking long-standing questions in plant defence. GLVs activate defence responses, potentially helping mitigate pest damage to crops. Scientists are now exploring how plants "smell" GLVs and how they use this info to protect themselves.

If you’ve enjoyed the smell of fresh cut grass, you may have unwittingly eavesdropped on a conversation between plants.

The smell is caused by a group of compounds called green leaf volatiles (GLVs) that a plant releases into the air when it is injured. Although it can be a very pleasant smell to humans, to other plants it may be a warning letting them know that danger is near.

Scientists have known for some time that plants can eavesdrop on damage to other plants nearby. Doing so can benefit a plant, which can take steps to defend itself. Scientists are considering harnessing this process to fight agricultural pests without having to use pesticides – although exactly how plants detect danger and protect themselves remains unknown.

Now, Masatsugu Toyota, a professor at Saitama University with a penchant for making microscopes, has found a way to ‘watch’ plants responding to these warning signals. The new study, published in Nature Communications on October 17, could help unlock long-standing questions in the field of plant defence and pave the way to protect crops without pesticides.

Abdul Rashid War, a scientist working on crop health at NatCo Pharma, explained that plants have two major defence mechanisms, involving a chain of molecular reactions. The reactions are triggered when a plant is damaged, he said, and GLVs are released as by-products. (By mounting a defence response, plants can make themselves less palatable or even indigestible to the insect attackers.) The molecular cascade is mediated by calcium, a common mediator of chemical and electrical signals found throughout biology.

When an insect takes a bite of a plant leaf, calcium ions flood the leaves in the cells. Dr. Toyota inserted a gene into the mustard plant (Arabidopsis thaliana), causing the plants’ cells to glow whenever they were flooded with calcium. When he placed the mutant plant under a special microscope rigged to detect fluorescent signals, he saw it light up in response to being touched, cut with a scissor or eaten by a caterpillar.

So if Dr. Toyota’s mutant mustard could eavesdrop on damage being done to another plant, it should also light up in response to GLVs.