Question

(a) Define geotropism. Give one example of geotropism.

(b) What is meant by 'positive geotropism' and 'negative geotropism'? Give one example of each type. Draw a lablled diagram to illustrate your answer indicating the plant part which shows positive geotropism and the plant part which shows negative geotropism.

(c) Name one plant part which exhibits positive thigmotropism.

Answer 1

Part (a): Geotropism:

1. The movement of plant parts in response to the direction of gravity is known as geotropism.
   
2. The growth of plant roots is an example of geotropism as it grows towards the direction of gravity.​

Part (b): Positive and negative geotropism:

1. If the movement of the plant parts is towards the pull of gravity, it is known as positive geotropism; whereas if the movement of the plant parts is in the direction opposite to the pull of gravity, it is known as negative geotropism.​
   
2. The movement of roots towards the soil is an example of positive geotropism.
3. The movement of plant stem away from the soil in the upward direction is an example of negative geotropism.​

Part (c): Example of thigmotropism:

1. Tendrils or climbing organs of a plant exhibit positive thigmotropism.​
2. These structures are found in plants with weak stems like pumpkins.