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Listen to an Academic Talk Test #085
Listen to an Academic Talk
1. What is the main subject of the lecture?
A) The ways plants grow in response to stimuli
B) The chemical composition of plant hormones
C) The process of photosynthesis in plants
D) The differences between various plant species
2. What does the lecturer say about the hormone auxin?
A) It is produced in the roots of a plant
B) It helps the plant absorb more water
C) It is evenly distributed throughout the stem
D) It accumulates on the shaded side of a plant stem
3. What can be inferred about a plant grown in zero gravity?
A) It would grow much faster than on Earth
B) Its roots and stem might grow in random directions
C) It would not be able to produce the hormone auxin
D) It would not need light to survive
4. What is the purpose of mentioning a plant in a window?
A) To describe an experiment with inconclusive results
B) To provide a familiar example of a tropism
C) To argue that plants should be kept outdoors
D) To explain how glass affects plant growth
Lecturer: Plants seem passive, but they actively respond to their surroundings through movements called tropisms. A tropism is a directional growth response to an external stimulus.
The most common one is phototropism—growth towards light. If you put a plant in a window, you'll see it bend towards the sunlight. 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 elongate, or grow longer, which physically pushes the tip of the stem toward the light.
Another example is gravitropism, the response to gravity. A plant's roots grow downwards, which is positive gravitropism, while the stem grows upwards, which is negative gravitropism. These simple responses are vital for survival, ensuring the plant maximizes its access to essential resources like light and water.
The most common one is phototropism—growth towards light. If you put a plant in a window, you'll see it bend towards the sunlight. 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 elongate, or grow longer, which physically pushes the tip of the stem toward the light.
Another example is gravitropism, the response to gravity. A plant's roots grow downwards, which is positive gravitropism, while the stem grows upwards, which is negative gravitropism. These simple responses are vital for survival, ensuring the plant maximizes its access to essential resources like light and water.
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