7.2 Electrical Signals

In 2018 it was demonstrated that whe– n a caterpillar or another herbivore eats a leaf, the plant produces a signal that rapidly spreads throughout its structure, activating defensive responses.

This signal depends on glutamate. In animals, glutamate is a key neurotransmitter for the nervous system. In plants, it plays a similar role: it binds to a specific receptor that triggers the activation of the signal.

In plants, this molecule acts as a wound signal: it binds to receptors that increase calcium concentration inside the cells, propagating the signal to distant organs. This signal involves charged calcium ions and is therefore electrochemical — partly comparable to the electrical signals travelling through animal neurons, though with different mechanisms and speed.

Even if slower and less complex, plants possess a molecular signalling system that allows them to perceive the environment and respond to it.

Is this extraordinary behaviour evidence of intelligence — or an automatic biochemical mechanism?