Mimosa pudica shows thigmonastic movement.

Thigmonastic movement, also known as "touch-induced movement," is a type of nastic movement that is triggered by mechanical stimulation. This movement is observed in various plants, including Mimosa pudica, commonly known as the sensitive plant or touch-me-not. The plant exhibits a fascinating response to touch, where its leaves fold inward and droop when subjected to external stimuli.

Response to touch:
When the sensitive plant's leaves are touched or disturbed, they rapidly fold up and droop. This response is an adaptive mechanism that helps protect the plant from potential harm, such as being eaten by herbivores or damaged by strong winds. The folding and drooping of the leaves reduce the plant's surface area, making it less visible and more difficult to access for potential threats.

Reason behind the movement:
The thigmonastic movement in Mimosa pudica is primarily driven by changes in turgor pressure within the plant cells. When the plant is touched, electrical signals are rapidly transmitted through specialized cells called pulvinus at the base of each leaflet. These electrical signals trigger the release of ions, including potassium ions, which lead to a decrease in turgor pressure in the leaf cells. As a result, the leaflets lose their rigidity and fold inward.

Role of pulvinus:
The pulvinus, which acts as a motor organ in the sensitive plant, is responsible for the movement of the leaves. It consists of specialized cells that can rapidly change their shape and volume. When stimulated, the pulvinus cells actively pump ions, water, and other solutes, leading to a rapid change in turgor pressure and the consequent folding of the leaflets.

Recovery and reorientation:
After the initial folding response, the Mimosa pudica plant gradually recovers its normal leaf position. This recovery process involves the redistribution of ions and water within the cells, which restores the turgor pressure and allows the leaflets to unfold. The reorientation of the leaves towards sunlight also occurs through thigmonastic movement, enabling the plant to optimize its photosynthetic activity.

Conclusion:
Mimosa pudica exhibits thigmonastic movement, a touch-induced response where its leaves fold inward and droop. This movement is driven by changes in turgor pressure within the plant cells, mediated by the pulvinus at the base of each leaflet. Understanding the mechanisms behind this type of movement helps us appreciate the intricacies of plant adaptations and their responses to environmental stimuli.