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Electrical security system helps tomato plants sound alarm when insects attack

When caterpillars, such as the pictured tomato hornworm, eat growing fruit, plants send electrical signals to the rest of the plant to signal the attack. Photo by Wikimedia Commons/CC
When caterpillars, such as the pictured tomato hornworm, eat growing fruit, plants send electrical signals to the rest of the plant to signal the attack. Photo by Wikimedia Commons/CC

July 20 (UPI) -- When caterpillars began munching on the fruits of a particular type of tomato plant, an electrical signal is sent from the fruit to the rest of the plant.

Most plant studies focus on the flow of nutrients and biochemical signals from plant to tomato, but for the latest study -- published Tuesday in the journal Frontiers in Sustainable Food Systems -- scientists set out to investigate the signal-sending capabilities of a plant's fruits.

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"We usually forget that a plant's fruits are living and semiautonomous parts of their mother-plants, far more complex than we currently think," first author Gabriela Niemeyer Reissig said in a press release.

"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?" said Niemeyer Reissig, a plant scientist at the Federal University of Pelotas in Brazil.

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"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," Niemeyer Reissig said.

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For the study, scientists grew tomato plants in a Faraday cage, an enclosure used to block electromagnetic fields. On the branches of the tomato plants, researchers installed electrodes linking fruits to the rest of the plant.

Scientists recorded and analyzed the electric signals produced by plants before, during and after 24 hours of exposure to Helicoverpa armigera caterpillars.

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The recordings showed signal patterns changed dramatically after caterpillars were introduced to the plants. Plants under attack also began producing higher concentrations of various defensive chemicals, including hydrogen peroxide.

Electrical and biochemical patterns showed even parts of the plant far from the caterpillar-caused damage were aware of the invasion and beefing up security.

For the now, the experiments were only able to offer a big-picture view of the plant's electrical signaling patterns. Scientists hope future experiments using machine learning algorithms will help them better understand the dynamics of individual electrical signals.

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"If studies like ours continue to advance and the techniques for measuring electrical signals in open environments continue to improve, it will be possible to detect infestation of agricultural pests quite early, allowing for less aggressive control measures and more accurate insect management," said Niemeyer Reissig.

"Understanding how the plant interacts with its fruits, and the fruits among themselves, may bring insights about how to 'manipulate' this communication for enhancing fruit quality, resistance to pests and shelf life after harvest," Niemeyer Reissig said.

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