Have you ever wondered why the roots of the plants always know which way to grow—into the soil but not above it? Some British scientists have recently solved this mystery.
It turns out that roots have special hairs that tie them into the soil and help them grow their way past obstacles, a team at the John Inners Center in Norwich reports in the February 29 issue of Journal Science.
“The key is in the fuzzy(有绒毛的)coat of hairs on the roots of plants,” says professor Liam Dolan. “We have found a growth control system that enables these hairs to find their way and to become longer when their path is clear.”
Root hairs explore the soil in much the same way a person would feel their way in the dark. If they come across an obstacle, they make their way around until they can continue growing in an opening. In the meantime, the plant is held in place as the hairs grip(紧紧抓住)the soil.
The hairs are guided by a clever chemical trick. A protein(蛋白质) at the tip of the root hairs called RHD2 helps them to take calcium(钙) from the soil. Calcium makes the hairs grow, and produce more RHD2, and take more calcium.
But when an obstacle blocks the hair’s path, or the hair reaches the surface of the soil, the cycle is broken and growth starts in another direction.
This system gives plants the flexibility to explore a complex environment and to live in even the most unpromising soils, says Dolan.
In poor soils such as in parts of Australia and Africa, native plants have adapted by producing enormous numbers of root hairs. A better understanding of this adaptation will allow scientists to develop hairy rooted crops that can grow in unfriendly environments.
According to Dolan, “Research in the John Inners Center is taking a breeding approach to increase hair length in wheat but it will be some time before new cultivars(栽培变种) are developed.”
【小题1】The passage is mainly about _______.

American beekeeping operations have been hit hard by what scientists call colony collapse disorder(C.C.D.). Almost half of their worker bees have disappeared during the past season. C.C.D. has also been reported in Israel, Europe and South America. Bees fly away from the hive and never return. Sometimes they are found dead; other times they are never found. Many crops and trees depend on pollination （授粉） by bees to help them grow.

A new report says virus may be at least partly responsible for the disorder in honey bee colonies in the United States. This virus is called Israeli acute paralysis virus. It was first identified in Israel in 2004. Ian Lipkin at Columbia University in New York and a team reported the new findings in Science magazine. Doctor Lipkin says the virus may not be the only cause. He says it may work with other causes to produce the collapse disorder.

The team found the virus in colonies with the help of a map of honey bee genes that was published last year. They examined thirty colonies affected by the disorder. They found evidence of the virus in twenty–five of them, and in one healthy colony. The next step is further testing of healthy hives.

The researchers suggested that the United States may have imported the disorder in bees from Australia. They say the bees may carry the virus but not be affected.

The idea is that unlike many American bees, the ability of Australian bees to fight disease has not been hurt by the varroa mite（全球性的蜂虱）. This insect attacks honey bees, which could make the disorder more likely to affect a hive. Australian bee producers reject these suspicions.

And some researchers suspect that bee production in the United States is down mainly because of the weather. Honey bees gather nectar（花蜜） from flowers and trees. The sweet liquid gives them food and material to make honey. But cold weather this spring in the Midwest reduced the flow of nectar in many flowers. Many bees may have starved. Dry weather in areas of the country could also be playing a part.

Wayne Esaias is a NASA space agency scientist who keeps bees in his free time. He lives in central Maryland, where he has found that flowers are blooming a month earlier than they did in 1970, which may be partly responsible for the disorder. Wayne Esaias is organizing a group of beekeepers to document nectar flow around the country.

1.The researchers found the virus ______.

2.What is the passage mainly about?

3.How many possibilities may be involved in the bee disorder according to the passage?

4.We can infer from the passage that ______.

In the summer of 1978 an English farmer was driving his tractor through a field of wheat when he discovered that some of his wheat was lying flat on the ground. The fattened (压平的) wheat formed a circle about six meters across. Around this circle were four smaller circles of flattened wheat. The five circles were in a formation like five dots. During the following years, farmers in England found the strange circles in their fields more and more often.
The circles are called “crop circles” because they appear in the fields of grain - usually wheat or corn. The grain in the circles lies flat on the ground but never broken; it continues to grow, and farmers can later harvest it. Farmers always discover the crop circles in the morning, so the circles probably form at night. They appear only in the months from May to September.
At first, people thought that the circles were a hoax. Probably young people were making them as a joke, or farmers were making them to attract tourists. To prove that the circles were a hoax, people tried to make circles exactly like the ones that farmer had found. They couldn’t do it. They couldn’t enter a field of grain without leaving tracks(痕迹), and they couldn’t flatten the grain without breaking it.
Many people believe that beings from outer space are making the circle to communicate with us from far away and that the crop circles are messages from them.
Scientists who have studied the crop circles suggested several possibilities. Some scientists say that a downward rush of wind leads to the formation of the circles - the same downward rush of air that sometimes causes an airplane to crash. Other scientists say that forces within the earth cause the circles to appear. There is one problem with all these scientific explanations: crop circles often appear in formations, like the five-dot formation. It is hard to believe that any natural force could form those.
【小题1】In the summer of 1978, an English farmer discovered in his field that __________.

In the 13^th century, the famous Italian traveler, Marco Polo, traveled a long way to China. During his stay in China, he saw many wonderful things. One of the things he discovered was that the Chinese used paper money. In western countries, people didn’t use the paper money until 15^th century. However, people in China began to use paper money in the 7^th century.
A Chinese man called Cai Lun invented paper almost 2,000 years ago. He took the wood from trees and made it into paper. He then put these pieces of paper together and made them into a book.
Now paper still comes from trees. We use a lot of paper every day. If we keep on wasting so much paper, there will not be any trees left on the earth. If there are no trees, there will be no paper. Every day, people throw away about 2,800 tons of paper in our city. It takes 17 trees to make one ton of paper. This means that we are cutting nearly 48,000 trees every day. Since it takes more than 10 years for a tree to grow, we must start using less paper now.
So how can we save paper? We can use both sides of every piece of paper, especially when we are making notes. We can use cotton handkerchiefs and not paper ones. When we go shopping, we can use fewer paper bags. If the shop assistant gives us a paper bag, we can save it and reuse it later.
Everyone can help to save paper. If we all think carefully, we can help protect trees. But we should do it now, before it is too late.
【小题1】 When he was in China, Marco Polo ____________.

A．discovered Cai Lun invented paper	B．learned to make paper
C．saw many wonderful things	D．read a lot of books

Bamboo（竹） is one of the nature’s most surprising plants. Many people call this plant a tree, but it is a kind of grass.
Like other kinds of grass, a bamboo plant may be cut very low to the ground, but it will grow back very quickly. A Japanese scientist recorded one bamboo plant that grew almost 1.5 meters in 24 hours! Bamboo grows almost everywhere in the world except Europe（欧洲）. There are more than 1,000 kinds of bamboo that grow around the world on both mountains and plains.
Not all bamboo looks the same. Some bamboo plants are very thin. They may only grow to be a few centimeters（厘米）wide while others may grow to more than 30 centimeters across. This plant also comes in different colors, from yellow to black to green.
Many Asian countries have been using bamboo for hundreds of years. They often use bamboo for building new buildings. As a matter of fact, the cables(绳索) hold up the hanging bridge across the Min River in Sichuan are made of bamboo. The bridge has been in use for more than 1,000 years, and is still holding strong.
In Africa, engineers are teaching poor farmers how to find water using bamboo. These African countries need cheap ways to find water because they have no money, and their fields often die from no rain and no water. It seems that bamboo is one of the best things they can use. Bamboo pipes and drills(钻) can help to make the poor thirsty fields be watered.
【小题1】How is bamboo like grass?