The leaves of touch-me-not plant (Mimosa pudica) are very sensitive, they droop on touching because of autotrophic effect. As, water within the cells of this plant applies a turgour pressure, which makes to leaves its stay upright. So, when any external pressure is applied like shaking or touching (seismonastic movement), activates the certain
contractile proteins including potassium ions. These chemicals make water and electrolytes flow/diffuse out of the cell, resulting in a loss of cell pressure. This causes the cell to collapse, which
squeezes the leaves close. Stimulus, in the form of touch is sometimes
transmitted to neighbouring leaves as well and causing the closing of other neighbour leaves too.