LONDON—Life for Cathy Hagner and her thr...

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.”

1.The passage is mainly about _______.

2.How does the circle work?

3.We can infer from the last paragraph that ________.

Five years ago, David Smith wore an expensive suit to work every day. “I was a clothes addict,” jokes. “I used to carry a fresh suit to work with me so I could change if my clothes got wrinkled.” Today David wears casual clothes---khaki pants and sports shirt---to the office. He hardly ever wears necktie. “I’m working harder than ever,” David says, “and I need to feel comfortable.”

More and more companies are allowing their office workers to wear casual clothes to work in the United States. The change from formal to casual office wear has been gradual. In the early 1990s, many companies allowed their employees to wear casual clothes on Friday (but only on Friday). This became known as “dress-down Friday” or “casual Friday.” “What started out as an extra one-day-a-week benefit for employees has really become an everyday thing,” said business consultant Maisly Jones.

Why have so many companies started allowing their employees to wear casual clothes? One reason is that it’s easier for a company to attract new employees if it has a casual dress code. “A lot of young people don’t want to dress up for work,” says the owner of a software company, “so it’s hard to hire people if you have a conservative dress code.” Another reason is that people seem happier and more productive when they are wearing comfortable clothes. In a study conducted by Levi Strauss and Company, 85 percent of employers said that they believe that casual dress improves employee morale. Only 4 percent of employers said that casual dress has a negative impact on productive. Supporters of casual office wear also argue that a casual dress code helps them save money. “Suits are expensive, if you have to wear one every day,” one person said. “For the same amount of money, you can buy a lot more casual clothes.”

1.David Smith refers to himself as having been “a clothes addict” because_______.

2.David Smith wears casual clothes now, because________

3.According to this passage, which of the following statements is FALSE?

4.In this passage, the following advantages of casual office wear are mentioned EXCEPT_______.

There are many ways to keep kids of all ages physically fit besides sports.

If your child is a natural athlete or ___1____ lover, he or she is probably already active and __2___ easy to get moving. But if, like me, you are the parent of a junior sofa potato, complete with a(n) __3____ controller in one hand and a bag of potato chips in the other, you know what it is like to have your ___4__ to go outside to play met with, at best, silence or at worst, cry and ___5___.

If logic, threats and lectures on health don’t work, turn to __6___: trick him or her into liking by making it into fun. __7____ enjoyment, not pressure or physical fitness or anything that seems to be “good for you”. That is where the dancing and nature walks ___8____. Health experts say that the answer to the question, “Which type of exercise is best for my child?” is “Whichever one he or she likes best.” It doesn’t have to be swimming or soccer or gymnastics. ____9___ play, especially with the rest of the family, will ___10___ the body’s requirements for regular aerobic movement (有氧运动) just well, and won’t ever seem like exercising.

___11____, if nature is an interest, walk vigorously around finding every leaf, insect, and _12___ print in the park. If rock radio is the station of choice, ___13____ to the music. Get the family members playing catch, touch football together. Organize a(n) __14____ science group to walk around your neighborhood and pick your rubbish. Make every trip to the pool an excuse for playing games in the water together.

Remember that the goal is to set a pattern for lifelong fitness. And if you don’t make it _15___, kids are never going to keep it up.

If I hadn’t stood under the ladder to catch you when you fell, you _____ now.

What an amazing ______! I was thinking about my cousin Lily when she phone me.