Question

What is the nastic movement? Give one example of each.

Answer 1

The nastic movements are those movements in plants that occur as the response to a stimulus but do not follow any specific direction of the stimulus. These are direction-independent movements and stimulus position has no effect on their direction. There are following types of nastic movements:

1. Seismonastic movements- These types of nastic movements occur in response to the mechanical stimuli of touch, contact, water pressure etc. For example, drooping of the leaves of Mimosa pudica when touched.
2. Photonastic movements- These occur in response to light but do not follow the direction of light. For example, the opening of petals of Cestrum nocturnum at night and closing during the day.
3. Thermonastic movements- These occur in response to the change and variation in temperature. For example, the leaves of rhododendrons curl up and close during low temperature.
4. Nyctinastic movements- These are also called sleeping movements because they occur in response to a change in day and night as well as the change in temperature. For example, the leaves of leguminous plants fold up and close in the evening and open in the morning.
5. Thigmonastic movement- These occur in response to contact of an object. For example, the insectivorous leaves of Drosera close when in contact with an insect.