The Very Hungry Caterpillar ate an apple, pears, plums, strawberries and oranges, but never a tomato.

Had it tried, then the unsuspecting insect would have triggered an innate defensive mechanism of the fruit, which would make it taste worse – according to a study.

Researchers, led by a team from Federal University of Pelotas in Brazil, have witnessed and described this clever mechanism for the first time.

They found that a tomato fruit has the inherent ability to sense a nearby insect and produce a cascade of electrical signals.

These warning impulses are sent to the main plant from the fruit and allow other parts of the plant to set up their own defences.

One of the botanical weapons it has at its disposal is the production of distasteful chemicals, which deliberately make the fruit less pleasant to fend off a hungry animal.

Hydrogen peroxide, the same chemical in bleach and hair dye, is one compound which increased in concentration after the electrical signals were triggered.

Preparing for a caterpillar attack

The finding helps revolutionise how we think of plants and their ability to communicate, the researchers say.

It has long been known that plants make and release chemicals to send messages, but usually it is from the plant to the fruit via the sap, not the other way round.

“Since fruits are part of the plant, made of the same tissues of the leaves and stems, why couldn’t they communicate with the plant, informing it about what they are experiencing, just like regular leaves do?” says Dr Gabriela Niemeyer Reissig, one of the report’s authors.

“What we found is that fruits can share important information such as caterpillar attacks – which is a serious issue for a plant – with the rest of the plant, and that can probably prepare other parts of the plant for the same attack.”

The researchers made the discovery by putting tomato plants in a Faraday cage with electrodes at the ends of each branch. This allowed them to measure the electrical impulses made by various parts of the plant, and where they were sent.

When caterpillars were introduced to the arena, the electrical signals changed drastically and so too did the chemicals produced by the plant.

The researchers now hope to see if other plants and fruits also have this ability. 

The findings are published in the journal Frontiers in Sustainable Food Systems.