『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 41 Lec 1听力练习：Why can annual plants grow in a desert even after a year of no rainfall?原文题目答案解析，TPO/Official 41 Lec 1听力原文范文音频翻译。

托福TPO/Official 41 Lec 1听力原文Why can annual plants grow in a desert even after a year of no rainfall?【新东方在线】

Narrator: Listen to part of the lecture in an environmental science class.

教授：许多生物已经发展了在恶劣环境中生存的能力：酷热、严寒，或者非常干燥的环境。

Professor: Many organisms have developed the ability to survive in harsh environmental conditions: extreme heat or cold, or very dry conditions.

你们的教科书中没有很多关于沙漠植物的具体细节，但我认为沙漠植物是能适应极端环境的很好的例子。

Your textbook doesn't have much about the specifics on desert plants, but I think that desert plants are great examples of specialized adaptations to extreme environmental conditions.

因此，对于沙漠植物，基本上有三种不同的适应策略。

So, with desert plants, there are basically three different adaptive strategies.

我应该指出，这些策略并不局限于任何特定的物种。

And I should point out that these strategies are not specific to any particular species.

许多不同的物种已经发展了其中特有的适应策略。

Many different species have developed each of the adaptations.

So, first of all, there are succulent plants.

有许多种肉质植物，但他们都可以吸收和储存大量的水。

There are many different species of succulent plants, but they all can absorb and store a lot of water.

显然，在沙漠中获得水的机会很少。

Obviously, opportunities to get water in the desert are few and far-between.

一般情况下，雨量很少且很短缺。

所以雨水就不会渗透到土壤深处

So the rain doesn't seep too far down into the soil.

在水分蒸发之前，任何植物获取水分的时间都是有限的。

And there's a limited window of time for any plant to get the water before it evaporates.

但是，肉质植物的根系分布广泛且较浅，可以迅速从土壤顶部几英寸处吸收水分， 尽管土壤必须保持湿润，因为肉质植物不擅长从只有一点湿润的土壤中吸收水分。

But succulent plants have a spread-out and shallow root system that can quickly pull in water from the top inches of soil, though the soil has to be saturated since succulents aren't good at absorbing water from soil that's only a little moist.

肉质植物也非常适合保存水分， 这在雨天稀少的环境中非常重要。

Succulent plants also are well suited to retaining water, important in an environment where rainy days are rare.

肉质植物可以将水储存在他们的叶子、茎干和根中。

Succulent plants can store water in their leaves, in their stems, or in their roots.

为了防止水分在炎热、干燥的环境中蒸发，大部分肉质植物有一层蜡质外层，使他们在气孔封闭时几乎是防水的。

And to keep that moisture from evaporating in the hot, desert Sun, most succulent plants have a waxy outer layer that makes them almost waterproof when their stomates are closed.

他们也通过最小化表面积来储水。

They also preserve water by minimizing their surface area.

植物暴露在阳光下的时间越长，就越有可能丢失其储存的水。

The more of the plant that's out in the Sun, the more potential there is to lose stored-up water.

这就意味着大部分肉质植物的叶子都很少。

And that means that most succulent plants have few, if any, leaves.

现在，除了肉质植物，还有耐旱植物。

Now, besides succulent plants, there're also drought-tolerant plants.

Drought-tolerant plants are like bears in a way.

你们知道熊在冬天大多都是在睡觉。

You know how bears mostly sleep through the winter.

他们可以不进食生存因为他们的新陈代谢减慢了。

They can survive without eating because their metabolism slows down.

耐旱植物也会进入休眠状态，当他们的主要资源，也就是水短缺的时候。

Well, drought-tolerant plants also go into a dormant state when resources, in their case, water, run short.

耐旱植物实际上在干枯时也不会死掉。

A drought-tolerant plant can actually dry out without dying.

我之前说过，沙漠中的雨大都小且少，但是偶尔也会有大雨。

I said before that most desert rains are light and brief, but occasionally there is a heavy one.

耐旱植物在一场大雨之后可以重新活过来。

Drought-tolerant plants revive after one of these significant rainfalls.

并且由于它们很深的根系，能够吸收大量的雨水

And they are able to absorb a good bit of the rainfall due to their deep roots.

实际上，耐旱植物的根系比生长在较为湿润的气候中的植物根系更广泛。

Actually the root system for drought-tolerant plants is more extensive than the root systems of many plants that live in wetter climates.

耐旱植物因其深根甚至可以从相对干燥的土壤中吸收水分，这一点和多肉植物不同。

Drought-tolerant plants can even absorb water from relatively dry soil because of their deep roots in contrast to succulent plants.

第三种适应策略是避免所有干旱条件。

The third adaptive strategy is to avoid the drought conditions altogether.

是的！有这样的植物：一年生植物！

Yes! There are plants that do this: Annual plants!

一年生植物会在的一个季节中成熟，结出种子，种子之后成为下一代的一年生植物。

An annual plant will mature and produce seeds in a single season that will become the next generation of annual plants.

在沙漠条件下，一年生植物生长在秋天或者春天，以避开夏天的炎热和冬天的寒冷。

In desert conditions, annual plants grow in the fall or spring to avoid the heat of summer and the cold of winter.

当然，这些植物可能会遇上一个严重的问题当某个秋天或者春天恰好非常干旱。

Of course, these plants could face a serious problem if a particular fall or spring happened to be very dry.

他们生长会很困难，可能会在结出种子之前死亡。

They would have difficulty growing and could die before producing seeds.

但他们有一个机制，以防止在降雨量少的年份灭绝。

But they have a mechanism to prevent one year of low rainfall from wiping them out.

并不是所有一年生植物的种子都在下一年长出来。

Not all seeds an annual plant puts out will grow the following year.

Some seeds remain dormant in the ground for several years.

这在生长环境恶劣、天气不适宜的季节对一年生植物是一种保障。

It's a type of insurance that protects the annual plants from a season of poor growing conditions, of unfavorable weather.

What are two features of succulent plants that help them survive in deserts? Click on two answers.

What is one ability that drought-tolerant plants have that succulent plants do not have?

Why can annual plants grow in a desert even after a year of no rainfall?

Listen to part of a lecture in an environmental science classMany organisms have developed the ability to survive in harsh environmental conditions, extreme heat or cold or very dry conditions, like plants in the desert. Your textbook doesn’t have much about the specific desert plants. But I think the desert plants are great examples as specialized adaptations to extreme environmental conditions. So with desert plants, there are basically three different adaption strategies. And I should point out the strategies are not specific to any particular species. Many different species have developed each of these adaptions. So first of all, there are succulent plants.There are many different species of succulent plants. But they all can absorb and store a lot of water. Obviously, opportunities to get water in the desert are few and far between. Generally, rains are light and short. So the rain doesn’t sink to far down into the soil. And there is a limited of time for any plant to get water before it evaporates. But succulent plants have spread out and shallow its root system that can quickly pull its water from the top and its soil. Though the soil has to be, since succulents aren’t good at absorbing water from soil that is only a little moist.Succulent plants are also well suited to retaining water, important in the environment where raining days are rare. Succulent can store water in their leaves, in their stems or in their roots. And to keep that moisture from evaporating in the hot desert sun, most succulent plants have wealthy out-layer, that makes almost waterproof when their are closed. They also preserve water by minimizing their surface area. The more of the plant is out in the sun, the more potential there is to lose stored-up water. And that means most succulent plants has few, if any, leaves.Now besides succulent plants, there are also drought-tolerant plants. Drought-tolerant plants are like bears in a way. You know how bears mostly sleep in the winter? They can survive without eating, because their metabolism slows down. Well, drought-tolerant plants also go into a dormant stay when resources, in their case, water run short. A drought-tolerant plant can actually dry out without dying. I said before that most desert rains are light and brief. But occasionally, there is a heavy one. Drought-tolerant plants revive after one of these significant rainfalls, and they are able to absorb a good bit of the rainfall due to their deep roots. Actually the root system for drought-tolerant plants is more extensive than the roots system of many plants that live in wetter climates. Drought-tolerant plants can even absorb water from relatively dry soil because of their deep roots, in contrast to the succulent plants.The third adaption strategy is to avoid the drought conditions all together. Yes, there are plants that do this, annual plants. An annual plant will mature and produce seeds in a single season. That will become the next generation of annual plants. In desert conditions, annual plants grow in the fall or spring to avoid the heat of summer and cold of winter. Of course, these plants could face serious problems if a particular fall or spring happens to be very dry. They would have difficulty growing and could die before producing seeds. But they have a mechanism to prevent one year of low rainfall from weeping them out. Not all seeds and annual plants puts out will grow the following year. Some seeds remain dormant in the ground for several years. It’s a type of insurance that protect the annual plants from the season of poor growing conditions of unfavorable weather. <img alt="" height="392" src="/upload/image/1516162281644.png" width="520" /><img alt="" height="389" src="/upload/image/1516162296326.png" width="521" /><img alt="" height="392" src="/upload/image/1516162307773.png" width="516" /><img alt="" height="388" src="/upload/image/1516162321134.png" width="518" />

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