400-820-0859Plants in salt marshes托福听力原文翻译及问题答案
一、Plants in salt marshes托福听力原文：
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托福听力中文翻译：
旁白：在海洋生物课上听一节课的一部分。女教授：好的，今天我们将继续讨论北美沿海盐沼的植物生活。盐沼是最不适合植物生长的环境之一。海水是咸的，几乎没有树荫，海潮进进出出，不断淹没沼泽……因此，在盐沼中发现的植物种类有限，但有一种植物属在那里繁衍生息——米草。
事实上，米草属是盐沼中的主要植物。你可以找到一种米草属植物，盐沼灯心草，生长在低沼泽地区。在较高的沼泽地区，你可能会发现一种通常被称为盐碱草甸干草的米草属植物。那么，在一个会杀死大多数植物的环境中，spartina是如何生存的呢？嗯，这是因为盐沼草找到了适应那里条件的方法。
首先，它们能够承受高盐环境。一个真正有趣的适应是反渗透过程的能力。通常，渗透过程是有效的……嗯……当水穿过植物细胞壁时，它会从含盐量最低的一侧移动到含盐量最高的一侧。
所以，想象一下，如果一个典型的植物突然发现自己在盐水中，会发生什么。植物细胞中所含的水，即含盐极少的水，会被抽向含盐较多的海水。所以你可以看到，植物中所含的淡水会被移除，植物会很快失去所有水分并脱水。但是，斯巴蒂纳人呢？嗯，它们允许一定量的盐进入细胞，使植物体内的水的含盐量略高于周围海水的含盐量。因此，海水中的盐不是从植物细胞中流出，而是进入反渗透，这实际上加强了细胞。另一种适应盐环境的能力是将多余的盐排泄回环境中。这就是为什么你可能会看到一棵在阳光下闪闪发光的；反射光线的不是海水中蒸发的盐，尽管这是一个很好的猜测。但实际上是植物内部的盐。很酷吧？下次你在盐沼里的时候，你真的可以用这一点给你的朋友和家人留下深刻印象。
但是，对付盐并不是盐沼植物面临的唯一挑战。那里的土壤很密，氧气含量很低。所以斯巴蒂纳人有气管。空气通过树叶上的小孔进入。这些管子为氧气提供了一条直接的管道，把氧气带到叶子下面，穿过茎，进入需要的根部。如果你拔起一棵米草属植物，你甚至可能会注意到一些根上有红色的泥。这是由于氧气与土壤中的硫化铁发生反应，产生氧化铁或铁锈。
现在，虽然spartinas已经适应了几种化学和物理机制，使它们能够在盐水中茁壮成长，并向根部供氧，但它们还必须适应恶劣环境的另一个方面：潮汐力和偶尔的猛烈风暴。风和水不断地冲击这些植物。因此，正如你可能猜到的，他们已经开发出一种将自己牢牢固定在土壤中的方法。
怎样嗯，它们有一种坚硬的地下茎叫做根茎。一种植物的根茎穿过泥泞的土壤生长，并与附近其他植物的根茎相互交错。植物形成了一种群体，一个可以生存或毁灭的群落，因为作为单一植物，它们无法单独生存。
当然，这些殖民地的植物也需要坚硬、有弹性的茎，茎可以弯曲很多，但不会因为水不断地冲入而折断。因此，除了互锁的地下根茎，它们还有另一种适应性，我们又回到了反渗透。
通过调节渗透压，使其细胞始终充分膨胀，植物能够在折断前承受巨大的压力。
三、Plants in salt marshes托福听力问题：
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托福听力答案：
A1:正确答案：B
A2:正确答案：A
A3:正确答案：D
A4:正确答案：B
A5:正确答案：A
A6:正确答案：A
