Leaflets of Mimosa pudica (common names: sensitive plant, touch-me-not) have a remarkable ability to close up in response to being touched or physically moved.
How fast can the leaflets close?
How does this occur?
And more importantly, what benefit could this unusual response provide to the plant?
If just the leaflets located toward the end of a leaf are touched, the adjacent leaflets close in fairly rapid succession until all leaflets on a leaf close up.
Explain how electrical signaling may be involved in this response.

Verified step by step guidance

1. Mimosa pudica exhibits a rapid plant movement known as thigmonasty, where the leaflets close in response to touch or physical disturbance.
2. The closing of the leaflets is facilitated by changes in turgor pressure within the pulvini, which are specialized motor cells located at the base of each leaflet.
3. When a leaflet is touched, an electrical signal, similar to an action potential in animals, is generated and travels through the plant tissue.
4. This electrical signal triggers the rapid efflux of potassium ions (K⁺) from the pulvini cells, leading to a loss of water and a decrease in turgor pressure, causing the leaflets to fold.
5. The closing of the leaflets may serve as a defense mechanism to deter herbivores or to reduce water loss by minimizing the surface area exposed to the environment.

Key Concepts

Thigmonasty

Thigmonasty refers to the non-directional movement of plant parts in response to touch or physical stimuli. In Mimosa pudica, this rapid movement is a defense mechanism against herbivores and environmental stress. The movement is caused by changes in turgor pressure within the plant cells, leading to the folding of leaflets.

Electrical Signaling in Plants

Electrical signaling in plants involves the transmission of electrical impulses through plant tissues, similar to nerve impulses in animals. In Mimosa pudica, these signals trigger rapid changes in cell turgor pressure, causing the leaflets to close. This signaling is facilitated by ion channels and changes in membrane potential, allowing for quick communication across the plant.

Adaptive Advantage of Leaflet Closure

The ability of Mimosa pudica to close its leaflets provides several adaptive advantages. It can deter herbivores by making the plant appear less appealing or by startling them. Additionally, leaflet closure can reduce water loss and protect the plant from environmental stressors like heavy rain or wind, enhancing its survival in various habitats.