AP BIOLOGY

Detailed explanation-1: -sensitive plant, (Mimosa pudica), also called humble plant, plant in the pea family (Fabaceae) that responds to touch and other stimulation by rapidly closing its leaves and drooping.

Detailed explanation-2: -When we touch Mimosa pudica (touch me not ), our touch acts as stimulus for plant and it closes its leaves in return. Some chemicals are released from the stem when we touch the plant. These chemicals force water to move out of the cell leading to the loss of turgor pressure. As a result, leaves droop.

Detailed explanation-3: -Leaves of the sensitive plant wilt and droop down on a slight touch due to turgor movement. Petiole of the sensitive plant is held up by turgid pulvinus tissue. The stimulus of touch leads to loss of turgor at the base of the leaflets and at the base of the petioles i.e. pulvinus.

Detailed explanation-4: -The folding up of leaves in a sensitive plant on touching is not a tropism because it is a non-directional movement. Tropism is a directional movement where the direction of the movement of the plant part is towards the stimulus.

Detailed explanation-5: -It is hypothesized that this rapid folding deters herbivores and insects from eating the plant by making the plant appear smaller, while simultaneously exposing the sharp spines on the plant stems.