Plants in salt marshes托福聽力原文翻譯及問題答案

Plants in salt marshes托福聽力原文翻譯及問題答案

一、Plants in salt marshes托福聽力原文：

Narrator:Listen to part of a lecture in a marine biology class.Female Professor:OK,today we’re going to continue our discussion of plant life in coastal salt marshes of North America.Salt marshes are among the least inviting environments for plants.The water is salty,there’s little shade,and the ocean tide comes in and out,constantly flooding the marsh…so the variety of plants found in salt marshes is limited,but there is a plant genus that thrives there—the spartina.

In fact,the spartina genus is the dominant plant found in salt marshes.You can find one type of spartina,salt marsh cordgrass,growing in low marsh areas.In higher marsh areas you’re likely to find a spartina commonly called salt meadow hay.So how is the spartina able to survive in an environment that would kill most plants?Well,it’s because salt marsh grasses have found ways to adapt to the conditions there.

First of all,they’re able to withstand highly saline conditions.One really interesting adaptation is the ability to reverse the process of osmosis.Typically the process of osmosis works…well…When water moves through the wall of a plant cell,it will move from the side containing water with the lowest amount of salt into the side containing the highest amount of salt.

So,imagine what would happen if a typical plant suddenly found itself in salt water.The water contained in the plant’s cells—that’s water with very little salt—would be drawn out toward the seawater—water with a lot of salt.So you can see,the freshwater contained in the plant would be removed and the plant would quickly lose all its water and dehydrate.But,what about the spartinas?Well,they allow a certain amount of salt to enter their cells,bringing the salt content of the water within the plant to a slightly higher concentration than that of the surrounding seawater.So instead of freshwater moving out of the plant’s cells,salt from the seawater enters,—reverse osmosis—and this actually strengthens the cells.Another adaptation to the salty environment is the ability to excrete excess salt back into the environment.That’s why you might see a spartina shimmering in the sunlight.  What’s reflecting the light is not salt from seawater that has evaporated—although that’s a good guess.But it’s actually the salt that came from within the plant.Pretty cool,huh?You can really impress your friends and family with that little tidbit the next time you’re in a salt marsh.

But coping with salt is not the only challenge for plants in a salt marsh.Soil there is dense and very low in oxygen.So spartinas have air tubes.Air enters through tiny openings on the leaves.The tubes provide a direct pipeline for the oxygen,carrying it down the leaves,through the stems and into the roots,where it’s needed.If you pull up a spartina,you might even notice some reddish mud on some of the roots.This is caused by oxygen reacting with iron sulfide in the soil and it produces iron oxide,or rust.

Now although the spartinas have adapted several chemical and physical mechanisms that allow them to thrive in salt water and to feed oxygen to their roots,there’s yet another aspect of the harsh environment that they’ve had to adapt to:the force of the tides and occasional violent storms.Wind and water are constantly crashing into these plants.So as you might have guessed,they’ve developed a means of solidly anchoring themselves into the soil.

How?Well,they have tough sort of…uh…underground stems called rhizomes.Rhizomes from one plant grow through the muddy soil and interlock with those of other nearby plants.The plants form a kind of colony,a community that will survive or perish together,because alone,as single plants,they cannot survive.

Of course,the plants in these colonies also need tough,resilient stems above the soil,stems that can bend a lot but not break as water constantly crashes into them.So in addition to the interlocking underground rhizomes,they have yet another adaptation and it’s,well,we’re back to reverse osmosis again.

By adjusting the osmotic pressure so that its cells are always fully inflated the plant is able to withstand great pressure before snapping.

二、Plants in salt marshes托福聽力中文翻譯：

旁白：在海洋生物課上聽一節(jié)課的一部分。女教授：好的，今天我們將繼續(xù)討論北美沿海鹽沼的植物生活。鹽沼是最不適合植物生長的環(huán)境之一。海水是咸的，幾乎沒有樹蔭，海潮進進出出，不斷淹沒沼澤……因此，在鹽沼中發(fā)現(xiàn)的植物種類有限，但有一種植物屬在那里繁衍生息——米草。

事實上，米草屬是鹽沼中的主要植物。你可以找到一種米草屬植物，鹽沼燈心草，生長在低沼澤地區(qū)。在較高的沼澤地區(qū)，你可能會發(fā)現(xiàn)一種通常被稱為鹽堿草甸干草的米草屬植物。那么，在一個會殺死大多數(shù)植物的環(huán)境中，spartina是如何生存的呢？嗯，這是因為鹽沼草找到了適應那里條件的方法。

首先，它們能夠承受高鹽環(huán)境。一個真正有趣的適應是反滲透過程的能力。通常，滲透過程是有效的……嗯……當水穿過植物細胞壁時，它會從含鹽量最低的一側移動到含鹽量最高的一側。

所以，想象一下，如果一個典型的植物突然發(fā)現(xiàn)自己在鹽水中，會發(fā)生什么。植物細胞中所含的水，即含鹽極少的水，會被抽向含鹽較多的海水。所以你可以看到，植物中所含的淡水會被移除，植物會很快失去所有水分并脫水。但是，斯巴蒂納人呢？嗯，它們允許一定量的鹽進入細胞，使植物體內的水的含鹽量略高于周圍海水的含鹽量。因此，海水中的鹽不是從植物細胞中流出，而是進入反滲透，這實際上加強了細胞。另一種適應鹽環(huán)境的能力是將多余的鹽排泄回環(huán)境中。這就是為什么你可能會看到一棵在陽光下閃閃發(fā)光的；反射光線的不是海水中蒸發(fā)的鹽，盡管這是一個很好的猜測。但實際上是植物內部的鹽。很酷吧？下次你在鹽沼里的時候，你真的可以用這一點給你的朋友和家人留下深刻印象。

但是，對付鹽并不是鹽沼植物面臨的唯一挑戰(zhàn)。那里的土壤很密，氧氣含量很低。所以斯巴蒂納人有氣管?？諝馔ㄟ^樹葉上的小孔進入。這些管子為氧氣提供了一條直接的管道，把氧氣帶到葉子下面，穿過莖，進入需要的根部。如果你拔起一棵米草屬植物，你甚至可能會注意到一些根上有紅色的泥。這是由于氧氣與土壤中的硫化鐵發(fā)生反應，產生氧化鐵或鐵銹。

現(xiàn)在，雖然spartinas已經(jīng)適應了幾種化學和物理機制，使它們能夠在鹽水中茁壯成長，并向根部供氧，但它們還必須適應惡劣環(huán)境的另一個方面：潮汐力和偶爾的猛烈風暴。風和水不斷地沖擊這些植物。因此，正如你可能猜到的，他們已經(jīng)開發(fā)出一種將自己牢牢固定在土壤中的方法。

怎樣嗯，它們有一種堅硬的地下莖叫做根莖。一種植物的根莖穿過泥濘的土壤生長，并與附近其他植物的根莖相互交錯。植物形成了一種群體，一個可以生存或毀滅的群落，因為作為單一植物，它們無法單獨生存。

當然，這些殖民地的植物也需要堅硬、有彈性的莖，莖可以彎曲很多，但不會因為水不斷地沖入而折斷。因此，除了互鎖的地下根莖，它們還有另一種適應性，我們又回到了反滲透。

通過調節(jié)滲透壓，使其細胞始終充分膨脹，植物能夠在折斷前承受巨大的壓力。

三、Plants in salt marshes托福聽力問題：

Q1:1.What is the lecture mainly about?

A.The effect of the tidal flow on the salt marsh

B.Ways that some plants have adapted to living in salt marshes

C.The process of osmosis in plants

D.Differences between plants that grow in salt marshes and plants that grow elsewhere

Q2:2.What is one result of reverse osmosis in the spartina?

A.Salt from seawater strengthens the plant's cells.

B.All parts of the plant are able to receive oxygen.

C.Salt evaporates off the stems and leaves of the plant.

D.Water is unable to move across the plant cell walls.

Q3:3.Why does the professor mention reddish mud on the roots of a spartina?

A.To illustrate the high density of salt-marsh soil

B.To explain how spartina rhizomes move through the soil

C.To point out the problems spartinas face in getting fresh water

D.To provide evidence that oxygen is present in the spartina s roots

Q4:4.In what way are rhizomes important for spartinas?

A.They allow plants to remain cool in direct sunlight.

B.They reduce the possibility of plants being uprooted during storms.

C.They help plants in dense soil process oxygen.

D.They reduce the concentration of salt in the surrounding seawater.

Q5:5.What can be inferred about the process that prevents spartinas from breaking in violent storms?

A.It is the same process that helps them survive being immersed in saltwater.

B.The process is also responsible for causing their air tubes to form.

C.The process sometimes damages their rhizomes.

D.Many other plants have developed a similar process.

Q6:6.Why does the professor say this:

A.To point out an incorrect conclusion.

B.To clarify the meaning of a term.

C.To admit that there is little evidence of the phenomenon she just described.

D.To emphasize the difference between a fact and an opinion.

四、Plants in salt marshes托福聽力答案：

A1:正確答案：B

A2:正確答案：A

A3:正確答案：D

A4:正確答案：B

A5:正確答案：A

A6:正確答案：A

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