Primed for defence with just a caress

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Janet Braam

Just by being touched, some plants will start churning out hormones that give herbivores a sore stomach.

Scientists from Rice University in Houston, Texas, have found that a touch is all that’s required to trigger the production of the natural insecticide jasmonate, which has long been known to be responsible for defence against herbivores in many plants, such as rice, tobacco and tomatoes. When these plants are touched by insects or foraging animals, jasmonates are rapidly prepared to interfere with the digestive process of the grazer.

Previous research has shown that this chemical is also responsible for changing the growth patterns of plants, from making a tendril bend around a wire when one side is rubbed, to the wind’s ‘touch’ stunting the growth of trees on windswept bluffs. Perhaps the wind itself, which delivers fungal spores, inadvertently prepares plants for potential infection.

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