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Listen to an Academic Talk Test #015
Listen to an Academic Talk
1. What is the talk primarily about?
A) How plants produce energy from sunlight
B) The role of hormones in plant development
C) Plants' directional growth responses
D) The way plant roots absorb water
2. What does the professor say causes a plant stem to bend toward light?
A) Cells on the sunny side grow faster
B) Cells on the shaded side grow longer
C) The stem becomes heavier on one side
D) The plant is trying to avoid gravity
3. What can be inferred about the hormone auxin?
A) It is damaged by direct sunlight
B) It is evenly distributed in plant roots
C) Its effect depends on its location in the plant
D) It stops working when a plant is mature
4. Why does the professor mention both phototropism and gravitropism?
A) To show that some plants do not have tropisms
B) To illustrate two different types of tropisms
C) To argue that one tropism is more important
D) To explain how tropisms work against each other
Professor: Plants might seem stationary, but they are constantly adjusting their growth to respond to the world around them. This directional growth in response to an external stimulus is called a tropism.
Perhaps the most familiar example is phototropism—the tendency for a plant to grow towards a light source. This happens because a hormone called auxin builds up on the shaded side of the stem. This concentration of auxin causes the cells on the dark side to grow longer, effectively bending the stem toward the light.
Another important response is gravitropism, which is growth in response to gravity. A plant's roots show positive gravitropism, meaning they grow downward into the soil, while its stem shows negative gravitropism by growing upward, away from gravity.
These tropisms are fundamental survival mechanisms, ensuring a plant can access the sunlight it needs for photosynthesis and its roots can find water and anchor it securely.
Perhaps the most familiar example is phototropism—the tendency for a plant to grow towards a light source. This happens because a hormone called auxin builds up on the shaded side of the stem. This concentration of auxin causes the cells on the dark side to grow longer, effectively bending the stem toward the light.
Another important response is gravitropism, which is growth in response to gravity. A plant's roots show positive gravitropism, meaning they grow downward into the soil, while its stem shows negative gravitropism by growing upward, away from gravity.
These tropisms are fundamental survival mechanisms, ensuring a plant can access the sunlight it needs for photosynthesis and its roots can find water and anchor it securely.
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