Why Do Touch-Me-Not (Mimosa Pudica) Leaves Close When Touched?

Mimosa pudica bends upon being touched. This occurs due to changes in the turgor pressure in its cells. The behavior is a predator avoidance mechanism.

Mimosa pudica is a perennial herb of the Fabaceae pea family, native to Central and South America. Commonly called the touch-me-not plant, the sensitive plant, or the ‘Tickle Me plant’, it is known for closing its leaves or folding them inwards when touched.

These are called nastic movements – movements that occur in response to a stimulus. If the stimulus is a touch or contact stimulus such as the wind, they are called seismonastic movements or thigmonasty. If the stimulus is heat, they are called thermonastic movements. If they are light reactions, the movements are photonastic, while day and night-based movements are called nyctinastic movements.

Mimosa pudica not only responds to seismonastic movements; it also closes upon being heated. When the plant is exposed to such stimuli, it undergoes a series of biochemical and bioelectrical changes that allow it to bend inwards.