(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
Answers
Explanation:
phototropism: The growth of the plant in the presnce of ligt Phototropism is due to the present of the auxin at the shoot part of the which inhibit the plant to grow laterally also know as "Negative geotrophism"
Geotrophism: The growth of the plant under the influence of gravity the auxin concentration is more at the root also called as "Positive geotrophism"
Role of auxin
•Inhibit the laterally growth of the plant
• flowering in pineapple
• control the xylem differentiation and help in cell division
Role of abscisic acid
•closure of stomata
•plant growth inhibitor and inhibitor of plant metabolism
Photo - Light and Geo - Gravity
Explanation:
Phototropism is the direction of the growth of a plant in response to the direction of the light.
Eg - Movement of a shoot of the plant upwards towards the light.
The positive activity of plants towards the gravity is known as Geotropism.
Eg - Root growing downward.
Auxin- It is responsible for the growth of the plant which is present at the shoot of the plant.
Auxin- Auxin has a wide range of uses in a plant.
- Abscisic acid- It inhibits the growth of the plant.
- Abscisic acid (ABA) is a plant hormone that functions mainly as a growth inhibitor.
- Abscisic acid promotes the dormancy in seeds and buds [ this is the opposite of breaking the dormancy].
- The closing of stomata is also dependent upon Abscisic Acid.
- Abscisic acid promotes falling of leaves.
