The Role of Ethylene托福聽力原文翻譯及問題答案

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The Role of Ethylene托福聽力原文翻譯及問題答案

一、The Role of Ethylene托福聽力原文：

W:Several of the processes related to growth and aging in plants involve the effects of hormones.Today I’ll talk about two aging processes—the ripening of fruit and the falling of leaves in autumn.These processes involve a hormone called ethylene.What is ethylene?It’s a chemical,a gas produced by plants as a hormone.Ethylene is unique among plant hormones because it’s the only hormone that’s a gas.The gaseous state is important because it enables ethylene to move through the plant.Like all other hormones,ethylene triggers certain responses in the plant.Ethylene is associated with a variety of aging processes.One example of the aging process is the ripening of fruit.The ripening of fruit involves several changes in structure and metabolism.Some of these changes are aging processes.One change is the weakening of cell walls,which softens the fruit.Another is the decrease in chlorophyll content,which causes the fruit to lose its greenness.Ethylene initiates or hastens both of these changes and also causes some ripened fruit to drop from the plant.A chain reaction occurs during ripening,as ethylene triggers aging.The aging cells then release more ethylene.Because ethylene is a gas,the signal to ripen spreads from fruit to fruit.You’ve heard the expression“One bad apple spoils the whole lot.”Well,it really is true!Yes,Randy?

M:So,when we buy fruit,like peaches that are still kind of green,and we store them in a plastic bag,and the peaches ripen faster—is this because of ethylene?I mean,I think I get it.The bag traps the ethylene gas,and this speeds up the ripening.

W:Right.That’s exactly what happens.Ethylene accumulates inside the plastic bag,and this starts a chain reaction.The signal to ripen spreads from one peach to another,and this causes all of the peaches to ripen faster.

By the way,the role of ethylene was discovered in sort of an interesting way.A century ago,citrus growers used to ripen fruit by“curing”it in sheds that were heated by kerosene stoves.The growers thought it was the heat from the stoves that ripened the fruit.However,they later discovered that the fruit didn’t ripen after they started using newer,cleaner-burning stoves.Botanists figured out that the reason the fruit ripened in the sheds with kerosene stoves was because of ethylene—not heat—because,as it turns out,ethylene is a by-product of kerosene combustion.Nowadays,a lot of fruit is ripened in huge storage containers that have ethylene gas piped in.It’s a new variation on the old curing shed.But in other cases,storage facilities have to slow down the ripening caused by natural ethylene.For example,apples are stored in bins that are flushed with carbon dioxide.Circulating the air with carbon dioxide prevents ethylene from accumulating,and carbon dioxide slows down the action of whatever ethylene isn’t flushed away.This is how apples can be stored for several months before they’re shipped to supermarkets.

Another aging process in plants where ethylene plays a role is the falling of leaves in autumn.When a leaf falls from a tree,the breaking point is a layer near the base of the leaf’s stalk.A change in the balance of two hormones—ethylene and auxin—controls the falling of leaves.An aging leaf produces less and less auxin,a hormone that stimulates cell growth.The drop in auxin makes the cells of the breaking layer more sensitive to ethylene.As the influence of ethylene becomes stronger,the cells start producing enzymes that weaken the cell walls of the breaking layer.Finally,with the help of wind or rain,the leaf breaks away at that layer and falls from the tree.

二、The Role of Ethylene托福聽力中文翻譯：

W：與植物生長和衰老有關(guān)的幾個過程涉及激素的影響。今天我來談?wù)剝蓚€衰老過程——果實成熟和秋季落葉。這些過程涉及一種名為乙烯的激素。乙烯是什么？它是一種化學(xué)物質(zhì)，是植物作為激素產(chǎn)生的一種氣體。乙烯在植物激素中是獨一無二的，因為它是唯一的氣體激素。氣態(tài)很重要，因為它能使乙烯在植物中移動。就像所有其他激素一樣，乙烯在植物中引發(fā)某些反應(yīng)。乙烯與各種衰老過程有關(guān)。衰老過程的一個例子是果實的成熟。果實的成熟涉及結(jié)構(gòu)和代謝的幾個變化。其中一些變化是衰老過程。一種變化是細胞壁的弱化，使果實軟化。另一種變化則是葉綠素含量的降低，導(dǎo)致果實失去綠色。乙烯引發(fā)或加速了這兩種變化，也導(dǎo)致一些成熟的果實從植物上脫落。在成熟過程中發(fā)生連鎖反應(yīng)，因為乙烯會引發(fā)衰老。然后衰老的細胞會釋放更多的乙烯。因為乙烯是一種氣體，成熟的信號會從一個水果傳播到另一個水果。你聽過“一個壞蘋果會毀掉整個蘋果”的說法。嗯，這真的是真的！是的，Randy？

M：所以，當(dāng)我們買水果時，比如仍然是綠色的桃子，我們把它們放在塑料袋里，桃子成熟得更快，這是因為乙烯嗎？我的意思是，我想我明白了。袋子會鎖住乙烯氣體，這會加速成熟。

W：對。這正是發(fā)生的事情。乙烯在塑料袋內(nèi)積聚，這會引發(fā)連鎖反應(yīng)。成熟的信號從一個桃子傳播到另一個桃子，這導(dǎo)致所有的桃子成熟得更快。

順便說一句，乙烯的作用是以一種有趣的方式被發(fā)現(xiàn)的。一個世紀前，柑橘種植者習(xí)慣于在用煤油爐加熱的棚子里“腌制”水果以使其成熟。種植者認為是爐子的熱量使水果成熟了。然而，他們后來發(fā)現(xiàn)，在開始使用更新、更清潔的爐灶后，水果并沒有成熟。植物學(xué)家發(fā)現(xiàn)，水果在有煤油爐的棚屋中成熟的原因是因為乙烯而不是熱量，因為事實證明，乙烯是煤油燃燒的副產(chǎn)品。如今，許多水果都是在巨大的儲存容器中成熟的，這些容器中有乙烯氣體。這是在舊的腌制棚上的一種新變種。但在其他情況下，儲存設(shè)施必須減緩天然乙烯引起的成熟。例如，蘋果被儲存在充滿二氧化碳的垃圾箱中。用二氧化碳循環(huán)空氣可以防止乙烯的積累，二氧化碳可以減緩任何沒有被沖走的乙烯的作用。這就是蘋果在運往超市之前可以儲存幾個月的方法。

乙烯起作用的植物的另一個衰老過程是秋季的落葉。當(dāng)樹葉從樹上掉落時，斷裂點是靠近樹干底部的一層。乙烯和生長素兩種激素平衡的變化控制著樹葉的掉落。衰老的葉子產(chǎn)生的生長素越來越少，生長素是一種刺激細胞生長的激素。生長素的下降使斷裂層的細胞對乙烯更敏感。隨著乙烯的影響越來越大，細胞開始產(chǎn)生酶，削弱破壞層的細胞壁。最后，在風(fēng)或雨的幫助下，葉子在破壞層脫落，從樹上掉下來。

三、The Role of Ethylene托福聽力問題：

Q1:1.What is the lecture mainly about?

A.The role of ethylene in plant aging processes

B.The discovery of ethylene by fruit growers 

C.Differences between ethylene and other hormones

D.How plant hormones influence growth

Q2:2.According to the professor,how is ethylene unique?

A.Ethylene is the only hormone that plants produce.

B.Ethylene is produced only in flowering plants.

C.Ethylene both stimulates and restricts plant growth.

D.Ethylene is the only plant hormone that is a gas.

Q3:3.According to the lecture,what are two effects of ethylene?

Click on two answers.

A.Fruit becomes softer as it ripens.

B.Plants develop complex root systems.

C.Trees shed their leaves in the fall.

D.Flower buds open in the spring.

Q4:4.Why does the professor say this:

A.To explain why she doesn’t like apples

B.To describe a common disease of fruit

C.To summarize the chain reaction of ripening

D.To caution against eating unwashed fruit

Q5:What does the professor imply about the falling of leaves?

A.Leaves fall from old trees,but not from trees that are still young.

B.Both hormones and environmental factors cause leaves to fall.

C.The falling of leaves increases the tree’s risk of getting a disease.

D.Spraying ethylene into an orchard will prevent leaves from falling.

四、The Role of Ethylene托福聽力答案：

A1:正確答案：A

A2:正確答案：D

A3:正確答案：AC

A4:正確答案：C

A5:正確答案：B

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