Plants' photoreceptors托福听力原文翻译及问题答案

Plants' photoreceptors托福听力原文翻译及问题答案

一、Plants' photoreceptors 托福听力原文：

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 托福听力中文翻译：

旁白：听植物学课上的部分讲座。女教授：好的。上次我们谈到光合作用，植物利用光将二氧化碳和水转化为食物的过程。今天我想谈谈光影响植物的另一种方式。我相信你们在物理课上都知道光是如何以微观方式运动的，我们只能在光的波长在特定范围内时才能看到光。此外，根据波长的不同，我们可以看到不同的颜色。

嗯，植物也能区分不同波长的光。现在，我不想把你弄糊涂。这不像植物有眼睛。植物看不到人类或动物那样的东西，但它们确实有光感受器。光感受器是通过发出化学信号对光作出反应的细胞。生物体，植物，对这个信号做出反应。事实上，植物从光感受器获得的信号有时会引起显着的反应。许多植物是季节性的。他们知道冬天什么时候结束，春天什么时候开始的一种方法是感知光线的变化。成年植物开花的时间取决于植物感觉到的光量。某些植物物种如果感觉到太多的光就不会开花，而有些植物只有在感觉到特定数量的光时才会开花。当然，这些都不是有意识的反应。这些植物只是以某种方式自动对光做出反应。植物还能够区分人眼甚至看不到的特定波长的光！特别是有一种波长叫做远红光。尽管他们为什么称之为远红色？我的意思是，它根本不是红色的。它位于光谱的红外范围内。我们看不到它，但植物可以将其感知为不同的波长。好啊现在我需要提到另一件关于光合作用的事情。我没有解释不同波长的光是如何影响光合作用的。当植物吸收光进行光合作用时，它只吸收一些波长的光，反射其他波长的光。植物吸收了大部分击中它们的红光，但植物只吸收了一些击中它们的远红光。它们反映了其余部分。记住这一点，因为这将与我要讨论的实验相关。这项引人入胜的实验表明，植物不仅可以检测特定波长的光并对其作出反应，还可以检测波长与波长之比的变化并对其作出反应。这个实验被称为潘帕斯实验。潘帕斯实验背后的想法与植物对其光感受器感知的红光与远红光比率变化的反应有关。一些生物学家假设，如果一种植物处于另一种植物的阴影下，它就会停止生长，当它感觉到红光与远红光的比例异常时，就会触发这种反应。好啊想象有两种植物。一个比另一个低。顶部的植物会吸收大部分红光进行光合作用，但会反射大部分远红光。这将导致树荫下的植物感觉到一个不寻常的比例。与正常情况相比，将出现更少的红光和更多的远红光。

这个比率意味着什么很重要。红光越少，红光越远，植物就会产生反应。它会停止长高，因为这种植物能感觉到它得不到足够的阳光来提供生长所需的能量。为了验证他们的假设，研究人员用了一些电灯，嗯。。。实际上，它们是发光二极管或LED。这些发光二极管可以模拟红光。所以他们把这些LED灯放在一些阴凉的植物周围。LED产生的光被植物感知为红色。

但是，与阳光不同，这些LED发出的光不支持光合作用。因此，这些植物感觉到红光与远红光的适当比例，并通过继续长高做出反应，而实际上这些植物并没有从光合作用中获得足够的能量来支持所有的生长。由于它们没有获得足够的能量来支持生长，大多数遮荫植物在短时间内死亡。

三、Plants' photoreceptors 托福听力问题：

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 托福听力答案：

A1:正确答案：C

A2:正确答案：B

A3:正确答案：D

A4:正确答案：C

A5:正确答案：A

A6:正确答案：B