Nastic Movement.

Nastic movement

Nastic movements are non-directional responses of plants to external stimuli. Unlike tactic movements, nastic movements do not depend on the direction of the stimulus but are triggered by the intensity or presence of the stimulus.

Characteristics of nastic movements

1. They are non-directional (not towards or away from the stimulus).
2. They occur in response to various stimuli such as light, temperature, and chemicals.
3. These movements can be caused by either:
   • Changes in turgor pressure (temporary movement).
   • Differential growth (permanent movement).
4. The rate or frequency of response increases with the intensity of the stimulus.

Types of nastic movements

Nastic movements can be categorized based on the nature of the stimulus:

1. Nyctinasty

• Definition: A type of nastic movement that occurs in response to changes in light intensity (photonasty) or temperature (thermonasty) during the day and night.
• Examples:
  1. Flower Opening and Closing: Certain flowers open during the day and close at night (e.g., Morning Glory flowers).
  2. Sleep Movements in Leaves: Leaves of leguminous plants fold at night and open during the day.

2. Thermonasty

• Definition: A type of nastic movement caused by changes in temperature.
• Examples:
  1. Some flowers close when the temperature drops (e.g., tulip petals close in cold temperatures).
  2. Some leaves fold when the temperature becomes too high to reduce water loss.

3. Chemonasty

• Definition: A nastic movement in response to chemical stimuli.
• Examples:
  1. Sundew Plants (Drosera): The glandular hairs of the plant fold around insects in response to chemicals released by the insect's body, trapping it.

4. Photonasty

• Definition: A type of nastic movement in response to light intensity.
• Examples:
  1. The opening and closing of flowers (e.g., sunflowers facing the sun).
  2. Some leaves fold or unfold depending on light availability (e.g., Oxalis leaves).