Nyctinasty

Nyctinasty

Diagram illustrating nyctinastic movement in plants.

Nyctinasty is a type of nastic movement in plants that occurs in response to the onset of darkness. This phenomenon is characterized by the movement of plant parts, such as leaves or petals, which open or close at night. Nyctinastic movements are typically driven by changes in turgor pressure within the plant cells and are often regulated by the plant's internal circadian rhythm.

Mechanism

Nyctinastic movements are primarily controlled by the plant's pulvinus, a specialized structure located at the base of the leaf or leaflet. The pulvinus contains motor cells that can rapidly change their turgor pressure, causing the leaf to move. During the day, these cells are turgid, keeping the leaves open to maximize photosynthesis. At night, the cells lose turgor pressure, causing the leaves to close.

The movement is often triggered by changes in light intensity, but it can also be influenced by temperature and humidity. The plant's internal circadian clock plays a crucial role in timing these movements, ensuring that they occur at the appropriate time of day.

Examples

Several plant species exhibit nyctinastic movements. One well-known example is the Mimosa pudica, commonly known as the "sensitive plant," which folds its leaves at night. Other examples include the prayer plant (Maranta leuconeura) and various species of legumes, such as the clover and bean plants.

Biological Significance

Nyctinasty is thought to provide several advantages to plants. By closing their leaves at night, plants may reduce water loss through transpiration and protect themselves from herbivory. Additionally, the movement may help protect the plant from pathogens and pests that are more active at night.

Related Movements

Nyctinasty is one of several types of nastic movements in plants. Other related movements include:

• Photonasty: Movement in response to light.
• Thermonasty: Movement in response to temperature changes.
• Thigmonasty: Movement in response to touch or mechanical stimulation.

Related Pages

• Circadian rhythm
• Turgor pressure
• Pulvinus
• Nastic movement