How does the sensitive plant detect the touch and how do the leaves move in response ?

Explanation

The sensitive plant (touch-me-not plant) shows visible movement in response to touch. This plant lacks nervous system and muscle tissue.
In a sensitive touch-me-not plant of the Mimosa family (chhui-mui), if we touch the leaves we find that all its leaves immediately fold up and droop.
Instead of specialised proteins or muscle cells, plant cells change the shape by changing the amount of water in them, resulting in swelling or shrinking. It results in folding up and drooping of leaves.
Thus, the sensitive plant detects the touch and its leaves move in response.