Why does the TickleMe plant move when tickled? What causes the leaves of the TickleMe plant (Mimosa pudica) to close and the branches to droop down?
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No one really knows exactly why the TickleMe plant moves, including scientists. However, it is thought to move in response to being tickled (or touched) due to the loss of turgor pressure, which is the force of the water and plant cell contents in the plant. This pressure gives the plant the ability to stand up straight without wilting. When a leaf is tickled, chemicals in the plant cause water to move out of some of the plant's cells. When water moves out of some of the cells, this reduces the turgor pressure and causes the leaflets and stalks to wilt. Some scientists believe these movements may be a form of protection from animals that attempt to eat it.