Question

Explain two tropic movements with suitable examples

Answer 1

Hint:Tropic movement defined as the movement of plants in response to stimuli. It shows some growth movements in response to stimulus.

Complete answer:
Phototropism:- Photo means 'light' and tropism means 'the direction in response of external stimulus'. So, phototropism is defined as the movement of an organism in response to light.
 If the organism responds towards the light, it is called positive phototropism.
For example, shoots of a plant always respond towards the sunlight. So, it is an example of positive phototropism. And away from light, is called negative phototropism. Root is the best example for negative phototropism.
Geotropism:- Geotropism also known as gravitropism. When the growth of a plant parts response to the force of gravity.
 The upward growth of the shoot is an example of negative geotropism and downward growth of a root is an example of positive geotropism.

Additional information:
There are many types of tropic movements in plants.
1. Phototropism (occurs in response to light)
2. Chemotropism (occurs in response to chemical substances)
3. Geotropism (occurs in response to gravity)
4. Thermotropism (occurs in response to temperature)
5. Hydrotropism (occurs in response to water)
6. Thigmotropism (occurs in response to mechanical stimulation).

Notes:The shoot tip is responsible for the directional movement towards the light and auxin(the growth hormone) can be found in this shoot tip ( meristematic) region. Auxin plays an important role in phototropism.