The Role of Ethylene托福听力原文翻译及问题答案

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The Role of Ethylene托福听力原文翻译及问题答案

一、The Role of Ethylene托福听力原文：

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托福听力中文翻译：

W：与植物生长和衰老有关的几个过程涉及激素的影响。今天我来谈谈两个衰老过程——果实成熟和秋季落叶。这些过程涉及一种名为乙烯的激素。乙烯是什么？它是一种化学物质，是植物作为激素产生的一种气体。乙烯在植物激素中是独一无二的，因为它是唯一的气体激素。气态很重要，因为它能使乙烯在植物中移动。就像所有其他激素一样，乙烯在植物中引发某些反应。乙烯与各种衰老过程有关。衰老过程的一个例子是果实的成熟。果实的成熟涉及结构和代谢的几个变化。其中一些变化是衰老过程。一种变化是细胞壁的弱化，使果实软化。另一种变化则是叶绿素含量的降低，导致果实失去绿色。乙烯引发或加速了这两种变化，也导致一些成熟的果实从植物上脱落。在成熟过程中发生连锁反应，因为乙烯会引发衰老。然后衰老的细胞会释放更多的乙烯。因为乙烯是一种气体，成熟的信号会从一个水果传播到另一个水果。你听过“一个坏苹果会毁掉整个苹果”的说法。嗯，这真的是真的！是的，Randy？

M：所以，当我们买水果时，比如仍然是绿色的桃子，我们把它们放在塑料袋里，桃子成熟得更快，这是因为乙烯吗？我的意思是，我想我明白了。袋子会锁住乙烯气体，这会加速成熟。

W：对。这正是发生的事情。乙烯在塑料袋内积聚，这会引发连锁反应。成熟的信号从一个桃子传播到另一个桃子，这导致所有的桃子成熟得更快。

顺便说一句，乙烯的作用是以一种有趣的方式被发现的。一个世纪前，柑橘种植者习惯于在用煤油炉加热的棚子里“腌制”水果以使其成熟。种植者认为是炉子的热量使水果成熟了。然而，他们后来发现，在开始使用更新、更清洁的炉灶后，水果并没有成熟。植物学家发现，水果在有煤油炉的棚屋中成熟的原因是因为乙烯而不是热量，因为事实证明，乙烯是煤油燃烧的副产品。如今，许多水果都是在巨大的储存容器中成熟的，这些容器中有乙烯气体。这是在旧的腌制棚上的一种新变种。但在其他情况下，储存设施必须减缓天然乙烯引起的成熟。例如，苹果被储存在充满二氧化碳的垃圾箱中。用二氧化碳循环空气可以防止乙烯的积累，二氧化碳可以减缓任何没有被冲走的乙烯的作用。这就是苹果在运往超市之前可以储存几个月的方法。

乙烯起作用的植物的另一个衰老过程是秋季的落叶。当树叶从树上掉落时，断裂点是靠近树干底部的一层。乙烯和生长素两种激素平衡的变化控制着树叶的掉落。衰老的叶子产生的生长素越来越少，生长素是一种刺激细胞生长的激素。生长素的下降使断裂层的细胞对乙烯更敏感。随着乙烯的影响越来越大，细胞开始产生酶，削弱破坏层的细胞壁。最后，在风或雨的帮助下，叶子在破坏层脱落，从树上掉下来。

三、The Role of Ethylene托福听力问题：

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托福听力答案：

A1:正确答案：A

A2:正确答案：D

A3:正确答案：AC

A4:正确答案：C

A5:正确答案：B

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