Researchers of a new study found that an injured leaf may send distress signals to other undamaged leaves when under threats such as being eaten. The fluorescent experiment shows how quickly plants’ internal communication really works.
Plant Distress Signals
Do plants actually know when they’re being eaten? A new study shows that plants can actually send out distress signals to other uninjured leaves when they are being attacked of eaten. The response is so fast that within seconds of the attack, the signal has already reached the other leaves, thereby prompting them to begin anticipatory defense responses.
In a video, blazes of fluorescent light can be seen issuing from the parts of a leaf being munched on by a caterpillar and travels over to the other uneaten leaves within seconds. The light is a chemical and electrical signal that prompts the other leaves to prepare for an attack.
In animals, nerve cells communicate with the help of glutamate. This happens when an excited nerve cell releases glutamate and triggers a wave of calcium ions from one nerve cell to another in a form of long-distance communication relay.
Evidently, a similar mechanism occurs when plants are under threat. When the leaf is wounded, it triggers the release of glutamate, which in turn activates a wave of calcium that travels from the local wound to other uninjured leaves as a sort of distress signal. Within minutes, researchers observed that the defense-related hormones were already spiked in distant leaves.
Fluorescent Electrical Signals
“We know there’s this systemic signaling system, and if you wound in one place the rest of the plant triggers its defense responses. But we didn’t know what was behind this system,” said Simon Gilroy of the University of Wisconsin-Madison, co-author of the study.
In this regard, researchers looked into the role of calcium in the electric movement that goes through the plant when it gets wounded. Calcium carries a charge, can produce an electrical signal, and often serves as a signal for a changing environment. To see the calcium movement in real time, the researchers bioengineered plants to produce a protein that only fluoresces in response to calcium. As a result, researchers were able to observe the calcium's movement in the plants’ system. This gave them a unique look into plants’ defensive strategy.
Interestingly, plant biologists were already aware that plants seem to know and sense it when there are changes to certain parts of the plant, but the mechanisms behind this internal communication was a mystery. Now, the researchers’ discovery opens up new doors into understanding the mechanisms behind plants’ internal communication and defense mechanisms.
The study is published in the journal Science and was completed by researchers from various institutions in the United States and Japan.