Why does the Touch-Me-Not plant (Mimosa pudica) closes its leaves when touched?
It is thought that the Touch-Me-Not (Mimosa pudica) plant closes its leaves when touched as a defense mechanism to prevent it selves from the insects or other herbivores. Nyctonastic movements, which are reactions that happen in absence of light, cause the Mimosa to close its leaves. The opening and closing of the leaves is controlled by a fluid-filled sac like structures found at the base of the leaves and each leaflet. The swollen base of the leaf is called as pulvinus. When the plant is touched, electrical signals are produced by the cells. The cells in the `pulvinus’ respond to this signal by flushing out potassium and water to the adjacent cell. With the massive loss of water, the leaves become flaccid and the pulvinus bends over and the leaflets fold. This causes the leaves of the plant to close. If the leaves are left undisturbed for few seconds, they open again.