Lecture 2 光合作用
Wors Tips
photosynthesis n.光合作用 convert v.使转换，转变
range n.范围 photoreceptor n.光感受器，感光器
infrared adj.红外线的 spectrum n.光谱，范围，系列
identicalto 相同的，同样的 wavelength n.波长，波段
organism n.生物体，有机体 relevant adj.相关的，切题的，中肯的
microscopic adj.显微镜的，极小的，微观的
Listen to the following recording and answer questions 1-4.
1）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
2）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 plant’s rate of photosynthesis increases.
3）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.
4）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.
听力原文
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.
Questions：
1.What is the lecture mainly about？
2.According to the professor，what is the one way that a plant reacts to changes in the period of sunlight？
3.Why does the professor think it inappropriate for certain wavelengths of light to be named“far-red”？
4.What points does the professor make when she discusses the red light and far-red light that reaches plants？
参考译文
好了，上次我们讲了光合作用，即植物用光把二氧化碳和水转化成食物的过程。今天我想讲讲光影响植物的另一种方式。
我相信你们从物理课上都知道了光是怎样做微观运动的，只有在光的波长达到特定范围时，我们才能看见光。还有，根据波长不同，我们看到的颜色也不同。植物也能分辨出不同波长的光。我不想把你们搞糊涂。不是说植物有眼睛。植物不像人或动物一样能看到光，但植物有光感受器。光感受器是一种细胞，遇光后会发出一种化学信号。生物体，或说植物，会对信号产生反应。事实上，植物从光感受器接收的信号有时候会让其产生剧烈反应。
很多种植物是季节性的，它们感知冬去春始的一种方式就是感应光的变化。成年植物开花的时间由植物感受到的光量而定。一些植物在它们感受到过强的光时，是不会开花的，还有一些只会在感受到一定的光量时才会开花。当然了，这些都不是有意识的反应。这些植物遇光后自动以某些方式做出反应。植物还能分辨出一些特殊波长的光，这些光人眼是看不见的。特别是一种称为远红的波长。为什么叫远红……我是说，这种光根本不是红色的。这种光在光谱上处于红外谱段。我们看不见这种光，但植物能感受到这种不同的波长。
好了，现在我要提到光合作用的另一方面。我没有解释不同波长的光是怎么影响光合作用的。植物吸收光进行光合作用时，它只吸收某些波长的光，反射别的光。植物吸收绝大多数接触到的红光，但只吸收部分接触到的远红光。其他光会被植物反射。记住这点，这和我将要讲的实验有关。
参考答案
1.C 2.B 3.D 4.C