Describe different types of nastic movements with one example from each.

Nastic movements are movements in plants caused by the intensity of a stimulus like light, temperature, touch, or chemicals — but not by its direction.
These movements usually occur in mature parts of plants due to changes in turgor pressure.

Types of Nastic Movements:

(i) Photonasty (Light):

• Caused by change in light intensity.
• Example: Lotus and Water lily open in sunlight and close at night.
• This helps the plant carry out photosynthesis during the day.

(ii) Thermonasty (Temperature):

• Caused by change in temperature.
• Example: Tulip and Crocus flowers open in warmth and close in cold.
• This protects the inner parts of flowers from temperature changes.

(iii) Chemonasty (Chemicals):

• Caused by chemical substances.
• Example: Sundew (Drosera) bends its sticky hairs toward the insect when it senses nitrogen compounds.

(iv) Seismonasty (Touch or Shock):

• Caused by mechanical stimuli like touch or vibration.
• Example: Mimosa pudica folds its leaves when touched.
• This happens because water leaves the cells in the pulvinus (leaf base), reducing turgor pressure.