Question

(i) What are nastic movements?

(ii) Why do these movements occur?

(iii) List their main features.

(iv) Give an example of any two nastic movements.

Answer 1

(i) Nastic Movements:

Nastic movements are paratonic or induced growth-dependent movements that occur in plants. Three common nastic movements observed in plants are scismonasty, photonasty and thermonasty.

(ii) Occurrence:

Nastic movements occur due to changes in the turgor pressure in the cells of plant organs.

(iii) Features of nastic movements:

The main features of nastic movements are that these movements-

1. Are temporary
2. Are reversible
3. Occur at a faster rate
4. Are independent of the direction of an external stimulus.

(iv) Examples:

Some examples of nastic movements are-

1. Scismonastic movement is exhibited by the touch-me-not plant when Its leaves fold and droop when touched.
2. Oxalis exhibits photonastic movements when its flowers close at night and open during the daytime.