Plants' photoreceptors托福聽力原文翻譯及問題答案

Plants' photoreceptors托福聽力原文翻譯及問題答案

一、Plants' photoreceptors 托福聽力原文：

NARRATOR: Listen to part of a lecture in a botany class.FEMALE PROFESSOR: OK. Last time we talked about photosynthesis, the process by which plants use light to convert carbon dioxide and water into food. Today I want to talk about another way light affects plants. I am sure you all know from physics class about how light moves in microscopic ways and that we can only see light when the wavelength of that light is in a specific range. Plus, depending on the wavelengths, we see different colors.

Well, plants are also capable of distinguishing between different wavelengths of light. Now, I don't want to confuse you. It is not like plants have eyes. Plants don't see in the sense that humans or animals do, but they do have photoreceptors.Photoreceptors are cells that respond to light by sending out a chemical signal. And the organism, the plant, reacts to this signal. In fact, the signals that plants get from their photoreceptors sometimes cause significant reactions.And many plants are seasonal. And one way they know when winter is ending and spring is beginning is by sensing the change in light. The time when an adult plant flowers is based on the amount of light the plant senses. Certain plant species won't flower if they sense too much light and some plants will only flower if they sense a specific amount of light.Of course, these aren't conscious reactions.These plants just automatically respond to light in certain ways.Plants are also able to distinguish between specific wavelengths of light that the human eye cannot even see! Specifically there's a wavelength called far-red.Although why they call it far-red ?I mean, it is not red at all. It lies in the infrared range of the spectrum. We can't see it, but plants can sense it as a different wavelength.OK. Now I need to mention another thing about photosynthesis.I didn't explain how different wavelengths of light affect photosynthesis.When a plant absorbs light for performing photosynthesis, it only absorbs some wavelengths of light and reflects others.Plants absorb most of the red light that hits them, but plants only absorb some of the far-red light that hits them. They reflect the rest. Remember this, because it's going to be relevant in an experiment I want to discuss.This fascinating experiment showed that plants not only detect and react to specific wavelengths of light, plants can also detect and react to changes in the ratio of one wavelength to another.This experiment was called the Pampas experiment.The idea behind the Pampas experiment had to do with the response of plants to changes in the ratio of red light to far-red light that the plants sense with their photoreceptors.Some biologists hypothesize that a plant will stop growing if it's in the shade of another plant, a reaction that's triggered when it senses an unusual ratio of red light to far-red light.OK. Imagine there are two plants. One below the other.The plant on top would absorb most of the red light for photosynthesis, but reflect most of the far-red light. That would lead to the plant in its shade sensing an unusual ratio. There will be less red light and more far-red light than normal.

What that ratio signifies is important. A ratio of less red and to more far-red light would cause a reaction from the plant. It would stop growing taller, because that plant could sense that it wasn't going to get enough sunlight to provide the energy to grow large.To test their hypothesis, researchers took some electrical lights, um...actually, they were light-emitting diodes, or LEDs. These light-emitting diodes could simulate red light. So they put these LEDs around some plants that were in the shade. The LEDs produce light that the plants sensed as red.

But, unlike sunlight, the light from these LEDs did not support photosynthesis. So the plants sensed the proper ratio of red light to far-red light and reacted by continuing to grow taller, while in reality these plants were not getting enough energy from photosynthesis to support all of that growth. And because they weren't getting enough energy to support their growth, most of the shaded plants died after a short time.

二、Plants' photoreceptors 托福聽力中文翻譯：

旁白：聽植物學(xué)課上的部分講座。女教授：好的。上次我們談到光合作用，植物利用光將二氧化碳和水轉(zhuǎn)化為食物的過程。今天我想談?wù)劰庥绊懼参锏牧硪环N方式。我相信你們在物理課上都知道光是如何以微觀方式運動的，我們只能在光的波長在特定范圍內(nèi)時才能看到光。此外，根據(jù)波長的不同，我們可以看到不同的顏色。

嗯，植物也能區(qū)分不同波長的光?，F(xiàn)在，我不想把你弄糊涂。這不像植物有眼睛。植物看不到人類或動物那樣的東西，但它們確實有光感受器。光感受器是通過發(fā)出化學(xué)信號對光作出反應(yīng)的細(xì)胞。生物體，植物，對這個信號做出反應(yīng)。事實上，植物從光感受器獲得的信號有時會引起顯著的反應(yīng)。許多植物是季節(jié)性的。他們知道冬天什么時候結(jié)束，春天什么時候開始的一種方法是感知光線的變化。成年植物開花的時間取決于植物感覺到的光量。某些植物物種如果感覺到太多的光就不會開花，而有些植物只有在感覺到特定數(shù)量的光時才會開花。當(dāng)然，這些都不是有意識的反應(yīng)。這些植物只是以某種方式自動對光做出反應(yīng)。植物還能夠區(qū)分人眼甚至看不到的特定波長的光！特別是有一種波長叫做遠(yuǎn)紅光。盡管他們?yōu)槭裁捶Q之為遠(yuǎn)紅色？我的意思是，它根本不是紅色的。它位于光譜的紅外范圍內(nèi)。我們看不到它，但植物可以將其感知為不同的波長。好啊現(xiàn)在我需要提到另一件關(guān)于光合作用的事情。我沒有解釋不同波長的光是如何影響光合作用的。當(dāng)植物吸收光進(jìn)行光合作用時，它只吸收一些波長的光，反射其他波長的光。植物吸收了大部分擊中它們的紅光，但植物只吸收了一些擊中它們的遠(yuǎn)紅光。它們反映了其余部分。記住這一點，因為這將與我要討論的實驗相關(guān)。這項引人入勝的實驗表明，植物不僅可以檢測特定波長的光并對其作出反應(yīng)，還可以檢測波長與波長之比的變化并對其作出反應(yīng)。這個實驗被稱為潘帕斯實驗。潘帕斯實驗背后的想法與植物對其光感受器感知的紅光與遠(yuǎn)紅光比率變化的反應(yīng)有關(guān)。一些生物學(xué)家假設(shè)，如果一種植物處于另一種植物的陰影下，它就會停止生長，當(dāng)它感覺到紅光與遠(yuǎn)紅光的比例異常時，就會觸發(fā)這種反應(yīng)。好啊想象有兩種植物。一個比另一個低。頂部的植物會吸收大部分紅光進(jìn)行光合作用，但會反射大部分遠(yuǎn)紅光。這將導(dǎo)致樹蔭下的植物感覺到一個不尋常的比例。與正常情況相比，將出現(xiàn)更少的紅光和更多的遠(yuǎn)紅光。

這個比率意味著什么很重要。紅光越少，紅光越遠(yuǎn)，植物就會產(chǎn)生反應(yīng)。它會停止長高，因為這種植物能感覺到它得不到足夠的陽光來提供生長所需的能量。為了驗證他們的假設(shè)，研究人員用了一些電燈，嗯。。。實際上，它們是發(fā)光二極管或LED。這些發(fā)光二極管可以模擬紅光。所以他們把這些LED燈放在一些陰涼的植物周圍。LED產(chǎn)生的光被植物感知為紅色。

但是，與陽光不同，這些LED發(fā)出的光不支持光合作用。因此，這些植物感覺到紅光與遠(yuǎn)紅光的適當(dāng)比例，并通過繼續(xù)長高做出反應(yīng)，而實際上這些植物并沒有從光合作用中獲得足夠的能量來支持所有的生長。由于它們沒有獲得足夠的能量來支持生長，大多數(shù)遮蔭植物在短時間內(nèi)死亡。

三、Plants' photoreceptors 托福聽力問題：

Q1:1.What is the lecture mainly about?

A. The differences in how humans and plants sense light

B. An explanation of an experiment on color and wavelength

C. How plants sense and respond to different wavelengths of light

D. The process by which photoreceptors distinguish wavelengths of light

Q2:2.According to the professor, what is one way that a plant reacts to changes in the number of hours of sunlight?

A. The plant absorbs different wavelengths of light.

B. The plant begins to flower or stops flowering.

C. The number of photoreceptors in the plant increases.

D. The plants’s rate of photosynthesis increases.

Q3:3.Why does the professor think that it is inappropriate for certain wavelengths of light to be named “far-red”?

A. Far-red wavelengths appear identical to red wavelengths to the human eye.

B. Far-red wavelengths have the same effects on plants as red wavelengths do.

C. Far-red wavelengths travel shorter distances than red wavelengths do.

D. Far-red wavelengths are not perceived as red by the human eye.

Q4:4.What points does the professor make when she discusses the red light and far-red light that reaches plants?

A. All of the far-red light that reaches plants is used for photosynthesis.

B. Plants flower more rapidly in response to far-red light than to red light.

C. Plants absorb more of the red light that reaches them than of the far-red light.

D. Red-light is absorbed more slowly by plants than far-red light is.

Q5:5.According to the professor, how does a plant typically react when it senses a high ratio of far-red light to red light?

A. It slows down its growth.

B. It begins photosynthesis.

C. It produces more photoreceptors.

D. It starts to release its seeds.

Q6:6.In the Pampas experiment, what was the function of the LEDs?

A. To simulate photosynthesis

B. To simulate red light

C. To add to the intensity of the sunlight

D. To provide additional far-red light

四、Plants' photoreceptors 托福聽力答案：

A1:正確答案：C

A2:正確答案：B

A3:正確答案：D

A4:正確答案：C

A5:正確答案：A

A6:正確答案：B

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