英语听力—环球英语 923 Growing Fruit in the Desert

　　Voice 1
Welcome to Spotlight¹. I’m Liz Waid.
Voice 2
And I’m Adam Navis. Spotlight uses a special English method of broadcasting. It is easier for people to understand - no matter where in the world they live.
Voice 1
In the last fifteen years, farmers in Israel were experiencing a serious problem. They were finding² it more and more difficult to grow their fruit crops. The earth was just too dry for their fruit trees. And it was hard for them to find extra supplies of water. Yosef Mizrahi is a farming expert. He told the BBC,
Voice 3
“Farmers in the desert had lost all of their money. They were removing their fruit trees. What we did in the past is not working any more. We had an insane³ idea: why not take desert plants, and make them into crops?”
Voice 2
The farmers needed to find a new way to grow crops in dry areas. So they turned to a desert plant, the cactus⁴, for help. Cacti⁵ need far less water than most normal plants. They have physical and structural⁶ qualities that set them apart from all other plants.
Voice 1
The farmers began using a special cactus that can produce fruit. It is called the nopal. It is also called the prickly pear. They added special fertilizers⁷, or plant growth chemicals, to the nopal. The nopal began producing fruit for eleven months out of the year.
Voice 2
So how are cactus plants able to grow so well in dry areas? How do they stay alive without a dependable water supply? Today’s Spotlight is on the cactus.
Voice 1
Most people recognize the cactus plant by its sharp spines⁸, or points. But there are other things that make the cactus plant different than other plants.
Voice 2
Scientists think that long ago the cactus looked much like any other plant. It had a stem⁹ which grew out of the ground. On the stem there were leaves. And, sometimes there were even flowers. But, over the years the seeds of cactus plants started to spread. They moved into more difficult places, including hot, dry deserts.
Voice 1
When cacti started to grow in dry areas they slowly began to change. Like all desert plants, cacti had to survive for long periods of time without water. Soon, the cacti’s stems¹⁰ started to grow thicker. The thick stem could store water.
Voice 2
The stem of a cactus is made up of many special cells. These cells store the water. The walls around each cell are very thin. So, the walls can stretch. When it rains these cells fill up with water. They stretch wide to make sure they are completely full. After a good rain, cacti are made of ninety percent water!
Voice 1
Over time there were other changes to the cactus plant. These changes helped the plant to survive even better in dry places. The stems became thicker and thicker. Soon, the chemical chlorophyll appeared in the stem.
Voice 2
Chlorophyll is very important to both plants and trees. People can usually find chlorophyll in a plant’s leaves. Chlorophyll gives leaves their green colour. But chlorophyll has another important purpose. It creates the plant’s food. The plant’s energy to stay alive comes from chlorophyll.
Voice 1
Once the chlorophyll moved to the cactus stem, the cactus no longer needed leaves. The leaves were actually a problem! The leaves were a barrier to the sun’s light. The chlorophyll in the stem could not receive enough sunlight through the leaves. Soon, cactus leaves became smaller and smaller. And today, there are usually no leaves growing from the cactus stem. The stem now produces food.
Voice 2
The leaves may have disappeared for another reason too. All plants lose water. Water evaporates¹² into the air from every part of a plant’s surface. So, a good way for a plant to survive in dry areas is to shrink¹³ its surface area. Then it loses less water. The cactus has a much better chance of surviving without the surface area of leaves.
Voice 1
For these reasons, the cactus plant also makes food in a different way than all other plants. Most plants use energy from the sun, carbon dioxide from the air, and water from the earth. Special holes, called pores¹⁴, cover the plant. During the day, the plant opens these pores to let in the sun and carbon dioxide. Immediately, the chlorophyll uses the sun’s energy and the carbon dioxide to make food. But the heat of the desert sun presents danger to the cactus plant. The heat could easily evaporate¹¹ the plant’s water.
Voice 2
So, the cactus performs a special trick. It does not open its pores during the day. Instead, the cactus opens up its pores at night. The temperature is cooler at night. So, the cactus loses less water. And, instead of using the carbon dioxide immediately, the cactus changes this gas into a liquid acid¹⁵ chemical. It stores the acid until morning. When the sun begins to rise, the cactus closes its pores again.
Voice 1
The next day the cactus uses the acid to create food. The chlorophyll gains energy from the sun through closed pores. This energy helps the chlorophyll use the acid to create food. As the day goes on, the cactus uses all of its stored acid. By the end of the day the cactus has lost most of its stored acid. So, it must repeat this process every night.
Voice 2
There are some animals that feed on desert cacti. But if an animal eats a cactus in the early morning, it will get a pain in its stomach! That is because they are eating the cactus when it is filled with acid!
Voice 1
Some desert plants send down long roots to get water from deep inside the ground. But cacti have a different root system. Their roots do not go deep down into the ground. Instead, cacti roots spread in all directions. The roots gather water from a very large area. Even a small cactus plant may send its roots a distance of nine to twelve metres from the area where it grows. There are scientists who study the roots of the desert cacti. They say something surprising. If we looked at the ground underneath¹⁶ a desert, it would look like a thick forest of roots!
Voice 2
Cacti are native to the Americas. Europeans first saw cactus plants when they discovered the New World. These travellers brought cacti home to Europe with them. Since then, people have planted cacti in many parts of the world. Now, you can find cacti growing in dry areas almost everywhere. They are a supply of food, water and beauty in many places.
 

1 spotlight   

n.公众注意的中心，聚光灯，探照灯，视听，注意，醒目

参考例句：

• This week the spotlight is on the world of fashion.本周引人瞩目的是时装界。
• The spotlight followed her round the stage.聚光灯的光圈随着她在舞台上转。

2 finding   

n.发现，发现物；调查的结果

参考例句：

• The finding makes some sense.该发现具有一定的意义。
• That's an encouraging finding.这是一个鼓舞人心的发现。

3 insane   

adj.蠢极的，荒唐的，精神错乱的，疯狂的

参考例句：

• Insane people are sometimes dangerous.精神病人有时非常危险。
• The letter made her insane with jealousy.那封信使她妒忌得发疯。

4 cactus   

n.仙人掌

参考例句：

• It was the first year that the cactus had produced flowers.这是这棵仙人掌第一年开花。
• The giant cactus is the vegetable skycraper.高大的仙人掌是植物界巨人。

5 cacti   

n.（复）仙人掌

参考例句：

• There we could see nothing but cacti.那里除了仙人掌我们什么也看不到。
• Cacti can survive the lack of rainfall in the desert.仙人掌在降水稀少的沙漠中也能生存下去。

6 structural   

adj.构造的，组织的，建筑（用）的

参考例句：

• The storm caused no structural damage.风暴没有造成建筑结构方面的破坏。
• The North American continent is made up of three great structural entities.北美大陆是由三个构造单元组成的。

7 fertilizers   

肥料，化肥( fertilizer的名词复数 )

参考例句：

• the long-term effects of fertilizers 肥料的长远影响
• Crushed bones make one of the best fertilizers. 骨粉是最佳肥料之一。

8 spines   

n.脊柱( spine的名词复数 )；脊椎；（动植物的）刺；书脊

参考例句：

• Porcupines use their spines to protect themselves. 豪猪用身上的刺毛来自卫。
• The cactus has spines. 仙人掌有刺。 来自《现代英汉综合大词典》

9 stem   

n.茎，干，船首，词干，血统；vt.堵住，阻止，抽去梗；vi.起源于，发生

参考例句：

• Cut the stem cleanly,just beneath a leaf joint.把茎切整齐点，正好切在叶根下。
• The ship was in a blaze from stem to stern.整艘船从头到尾都着火了。

10 stems   

n.（花草的）茎( stem的名词复数 )；词干；（高脚酒杯的）脚；烟斗柄v.遏制[阻止]（液体的流动等）( stem的第三人称单数 )；封堵；遏止

参考例句：

• The present wave of strikes stems from discontent among the lower-paid. 当前的罢工浪潮起因于低工资雇员们的不满情绪。 来自《简明英汉词典》
• Her interest in flowers stems from her childhood in the country. 她对花卉的兴趣产生于她在乡下度过的童年时代。 来自《简明英汉词典》

11 evaporate   

vi.蒸发，挥发，消失；vt.使蒸发，使挥发

参考例句：

• Clearly,the star wars problem was not going to evaporate.显然，星球大战问题并没有不了了之。
• It will evaporate like a spirit.它将来总要像幽灵一样化成云烟。

12 evaporates   

v.（使某物）蒸发掉( evaporate的第三人称单数 )；消失，不复存在；使脱水

参考例句：

• Heat evaporates water into steam. 水受热变成水蒸气。 来自《简明英汉词典》
• As the water evaporates, a crust of salt is left on the surface of the soil. 随着水分的蒸发，地面上留下了一层结晶盐。 来自辞典例句

13 shrink   

n.收缩，萎缩；vi.收缩，退缩，萎缩；vt.使收缩

参考例句：

• Washing wool in hot water will shrink it.在热水中洗毛织品会使其缩水。
• This cloth won't shrink when it's washed.这种布下水不缩。

14 pores   

（皮肤上的）毛孔，微孔( pore的名词复数 )

参考例句：

• The pores of your body secrete sweat. 身上的毛孔分泌汗液。
• Sweat exudes through the pores. 汗从毛孔中渗出。

15 acid   

n.酸；酸性物质；adj.酸的，酸性的

参考例句：

• Handle with care,or the acid may get out.小心轻放，否则酸会溢出来。
• The acid has been eating away the sides of the container.酸腐蚀着容器的四壁。

16 underneath   

adj.在...下面，在...底下；adv.在下面

参考例句：

• Working underneath the car is always a messy job.在汽车底下工作是件脏活。
• She wore a coat with a dress underneath.她穿着一件大衣，里面套着一条连衣裙。