Question

(a) What is (i) phototropism, and (ii) geotropism? With labelled diagrams, describe an activity to show that light and gravity change the direction that plant parts grow in.
(b) Mention the role of each of the following plant hormones:
(i) Auxin
(ii) Abscisic acid

Answer 1

(a) (i) The bending of shoots or other plant parts in response to light is known as phototropism.

(ii) The bending or growth of roots towards gravity is known as geotropism.

Activity -
Fill a conical flask with water and then cover the neck of the flask with a wire mesh. Place few germinating seeds on the wire mesh. Then, take a cardboard box that is open from one side. Place the flask in the box and keep this setup near a window. After 3-4 days, you will notice the shoots start bending towards light, while the roots bend away from light.

(b) (i) Auxin helps cells grow longer.

(ii) Abscisic acid inhibits growth and causes wilting of leaves.