A. What is meant by ‘tropisms’ ? Explain with an example.

B. Mention types of tropisms. Define each type of tropism. Write the name of stimulus in each case.

C. How do tropism differ from nastism?

(A) When a plant part gets moved in response to an external stimuli or directional stimuli, then it is known as tropism. If the growth of plant part is towards the stimulus then it is called positive tropism and when the growth is away from the stimulus, then it is called the negative tropism.

Example- Growth of stem towards the light is an example of positive phototropism. The plant part – stem grows in the response to light.

(B) There are 5 common types of tropism:

1. Phototropism- The movement of plant part in response to light is known as phototropism. The stimulus in this case is –light.

2. Hydrotropism- The movement of plants towards water is hydrotropism. The stimulus is water.

3. Geotropism- The movement of plants towards gravity is known as geotropism. The stimulus in geotropism is gravity.

4. Chemotropism- The movement of plants towards chemical stimulus is known as chemotropism. The stimulus is chemicals.

5 Thigmotropism- The movement of plants towards light is phototropism. The stimulus in thigmotropism is touch.

(C)