Question
Discuss with examples three types of tropic movements in plants.
Answer
Plants exhibit various tropic movements or directional growth responses in response to external stimuli such as light, gravity, touch, or moisture.
Here are three types of tropic movements in plants:
- Phototropism: Phototropism is the directional growth response of plants towards or away from a light source. Most plants exhibit positive phototropism, where the shoot grows towards the light, while the roots exhibit negative phototropism, growing away from the light. An example of a plant exhibiting phototropism is sunflowers. They move their heads to track the sun’s movement, to maximize their exposure to sunlight.
- Geotropism: Geotropism is the directional growth response of plants in response to gravity. Roots exhibit positive Geotropism, growing towards the direction of gravity, while shoots exhibit negative Geotropism, growing in the opposite direction. An example of a plant exhibiting Geotropism is the bean plant. When the plant is placed on its side, the roots curve and grow downwards while the stem curve and grows upwards, towards the direction of gravity.
- Thigmotropism: Thigmotropism is the directional growth response of plants in response to touch or mechanical stimuli. This movement can either be towards the stimulus or away from it, depending on the plant species. An example of a plant exhibiting thigmotropism is the Venus Flytrap. The leaves of the Venus Flytrap are lined with sensitive hairs, and when an insect lands on them and triggers the hairs, the leaves close around the insect, capturing it for digestion.
