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Listen to an Academic Talk Test #020
Listen to an Academic Talk
1. What is the main subject of the talk?
A) The process of photosynthesis in plants
B) How a plant hormone affects growth
C) The different parts of a plant's stem
D) The role of sunlight in a plant's life cycle
2. According to the professor, what does the hormone auxin do to plant cells?
A) It causes them to become longer.
B) It makes them more sensitive to light.
C) It helps them store more water.
D) It protects them from damage.
3. What would most likely happen to a plant that was lit evenly from all sides?
A) It would stop producing the hormone auxin.
B) It would grow much faster than normal.
C) It would likely grow straight up.
D) It would bend in a random direction.
4. Why does the professor begin by mentioning a houseplant on a windowsill?
A) To introduce the topic with a familiar example
B) To suggest the best way to care for plants
C) To describe an experiment she conducted
D) To prove that all plants need sunlight
Professor: Have you ever noticed how a houseplant on a windowsill seems to bend toward the light? This movement is a perfect example of what's called a tropism—a plant's directional growth in response to an external stimulus.
The specific response to light is called phototropism. It's controlled primarily by a plant hormone called auxin. When light shines on a plant, the auxin concentrates on the shaded side of the stem.
This higher concentration of auxin causes the cells on the shaded side to elongate, or grow longer, than the cells on the side receiving direct light. This difference in growth rate is what forces the stem to bend and grow toward the light source.
This is a positive phototropism, and it's a crucial survival mechanism, as it helps the plant maximize its exposure to light for photosynthesis.
The specific response to light is called phototropism. It's controlled primarily by a plant hormone called auxin. When light shines on a plant, the auxin concentrates on the shaded side of the stem.
This higher concentration of auxin causes the cells on the shaded side to elongate, or grow longer, than the cells on the side receiving direct light. This difference in growth rate is what forces the stem to bend and grow toward the light source.
This is a positive phototropism, and it's a crucial survival mechanism, as it helps the plant maximize its exposure to light for photosynthesis.
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