1.3 Plant Stimulus and Response Flashcards
What are the two main types of plant responses to stimuli?
- Tropism response: Directional growth towards or away from a stimulus.
- Nastic response: Non-directional movement in response to stimuli like touch, light, and heat.
What is phototropism, and give an example.
Phototropism is the growth of plant parts towards light.
- Example: Sunflower shoots grow in the direction of sunlight.
What is geotropism, and give an example.
Geotropism is the growth of plant parts towards gravity.
- Example: The roots of a red chili tree grow downward with gravity.
What is hydrotropism, and give an example.
Hydrotropism is the growth of plant parts towards water.
- Example: Pandan tree roots grow in the direction of water.
What is tigmotropism, and give an example.
Tigmotropism is the movement of plant parts in response to touch.
- Example: Cucumber tendrils wrap around objects they touch.
How does the nastic response differ from tropism?
Unlike tropism, the nastic response does not depend on the direction of the stimulus.
Give an example of a plant showing a nastic response.
The Mimosa pudica (semalu tree) closes its leaves when touched.
Why is phototropism important for plants?
It helps shoots get sunlight for photosynthesis, ensuring food production.
Why is geotropism important for plants?
It helps roots penetrate the soil to absorb water and anchor the plant firmly.
Why is hydrotropism important for plants?
It helps roots absorb water and mineral salts, essential for plant growth.
Why is tigmotropism important for climbing plants?
It allows plants to climb higher to reach sunlight and stay upright.
Why is nastic movement important?
It helps protect leaves from injury, such as in Mimosa pudica, which closes when touched.
